From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- Documentation/fb/api.rst | 307 ++++++++++++++ Documentation/fb/arkfb.rst | 68 +++ Documentation/fb/aty128fb.rst | 73 ++++ Documentation/fb/cirrusfb.rst | 94 +++++ Documentation/fb/cmap_xfbdev.rst | 56 +++ Documentation/fb/deferred_io.rst | 79 ++++ Documentation/fb/efifb.rst | 71 ++++ Documentation/fb/ep93xx-fb.rst | 136 ++++++ Documentation/fb/fbcon.rst | 354 ++++++++++++++++ Documentation/fb/framebuffer.rst | 353 ++++++++++++++++ Documentation/fb/gxfb.rst | 52 +++ Documentation/fb/index.rst | 52 +++ Documentation/fb/intel810.rst | 287 +++++++++++++ Documentation/fb/internals.rst | 86 ++++ Documentation/fb/lxfb.rst | 52 +++ Documentation/fb/matroxfb.rst | 438 ++++++++++++++++++++ Documentation/fb/metronomefb.rst | 38 ++ Documentation/fb/modedb.rst | 182 ++++++++ Documentation/fb/pvr2fb.rst | 66 +++ Documentation/fb/pxafb.rst | 173 ++++++++ Documentation/fb/s3fb.rst | 82 ++++ Documentation/fb/sa1100fb.rst | 37 ++ Documentation/fb/sh7760fb.rst | 130 ++++++ Documentation/fb/sisfb.rst | 160 +++++++ Documentation/fb/sm501.rst | 15 + Documentation/fb/sm712fb.rst | 35 ++ Documentation/fb/sstfb.rst | 204 +++++++++ Documentation/fb/tgafb.rst | 71 ++++ Documentation/fb/tridentfb.rst | 78 ++++ Documentation/fb/udlfb.rst | 169 ++++++++ Documentation/fb/uvesafb.rst | 188 +++++++++ Documentation/fb/vesafb.rst | 190 +++++++++ Documentation/fb/viafb.modes | 870 +++++++++++++++++++++++++++++++++++++++ Documentation/fb/viafb.rst | 297 +++++++++++++ Documentation/fb/vt8623fb.rst | 64 +++ 35 files changed, 5607 insertions(+) create mode 100644 Documentation/fb/api.rst create mode 100644 Documentation/fb/arkfb.rst create mode 100644 Documentation/fb/aty128fb.rst create mode 100644 Documentation/fb/cirrusfb.rst create mode 100644 Documentation/fb/cmap_xfbdev.rst create mode 100644 Documentation/fb/deferred_io.rst create mode 100644 Documentation/fb/efifb.rst create mode 100644 Documentation/fb/ep93xx-fb.rst create mode 100644 Documentation/fb/fbcon.rst create mode 100644 Documentation/fb/framebuffer.rst create mode 100644 Documentation/fb/gxfb.rst create mode 100644 Documentation/fb/index.rst create mode 100644 Documentation/fb/intel810.rst create mode 100644 Documentation/fb/internals.rst create mode 100644 Documentation/fb/lxfb.rst create mode 100644 Documentation/fb/matroxfb.rst create mode 100644 Documentation/fb/metronomefb.rst create mode 100644 Documentation/fb/modedb.rst create mode 100644 Documentation/fb/pvr2fb.rst create mode 100644 Documentation/fb/pxafb.rst create mode 100644 Documentation/fb/s3fb.rst create mode 100644 Documentation/fb/sa1100fb.rst create mode 100644 Documentation/fb/sh7760fb.rst create mode 100644 Documentation/fb/sisfb.rst create mode 100644 Documentation/fb/sm501.rst create mode 100644 Documentation/fb/sm712fb.rst create mode 100644 Documentation/fb/sstfb.rst create mode 100644 Documentation/fb/tgafb.rst create mode 100644 Documentation/fb/tridentfb.rst create mode 100644 Documentation/fb/udlfb.rst create mode 100644 Documentation/fb/uvesafb.rst create mode 100644 Documentation/fb/vesafb.rst create mode 100644 Documentation/fb/viafb.modes create mode 100644 Documentation/fb/viafb.rst create mode 100644 Documentation/fb/vt8623fb.rst (limited to 'Documentation/fb') diff --git a/Documentation/fb/api.rst b/Documentation/fb/api.rst new file mode 100644 index 000000000..4f00e7196 --- /dev/null +++ b/Documentation/fb/api.rst @@ -0,0 +1,307 @@ +=========================== +The Frame Buffer Device API +=========================== + +Last revised: June 21, 2011 + + +0. Introduction +--------------- + +This document describes the frame buffer API used by applications to interact +with frame buffer devices. In-kernel APIs between device drivers and the frame +buffer core are not described. + +Due to a lack of documentation in the original frame buffer API, drivers +behaviours differ in subtle (and not so subtle) ways. This document describes +the recommended API implementation, but applications should be prepared to +deal with different behaviours. + + +1. Capabilities +--------------- + +Device and driver capabilities are reported in the fixed screen information +capabilities field:: + + struct fb_fix_screeninfo { + ... + __u16 capabilities; /* see FB_CAP_* */ + ... + }; + +Application should use those capabilities to find out what features they can +expect from the device and driver. + +- FB_CAP_FOURCC + +The driver supports the four character code (FOURCC) based format setting API. +When supported, formats are configured using a FOURCC instead of manually +specifying color components layout. + + +2. Types and visuals +-------------------- + +Pixels are stored in memory in hardware-dependent formats. Applications need +to be aware of the pixel storage format in order to write image data to the +frame buffer memory in the format expected by the hardware. + +Formats are described by frame buffer types and visuals. Some visuals require +additional information, which are stored in the variable screen information +bits_per_pixel, grayscale, red, green, blue and transp fields. + +Visuals describe how color information is encoded and assembled to create +macropixels. Types describe how macropixels are stored in memory. The following +types and visuals are supported. + +- FB_TYPE_PACKED_PIXELS + +Macropixels are stored contiguously in a single plane. If the number of bits +per macropixel is not a multiple of 8, whether macropixels are padded to the +next multiple of 8 bits or packed together into bytes depends on the visual. + +Padding at end of lines may be present and is then reported through the fixed +screen information line_length field. + +- FB_TYPE_PLANES + +Macropixels are split across multiple planes. The number of planes is equal to +the number of bits per macropixel, with plane i'th storing i'th bit from all +macropixels. + +Planes are located contiguously in memory. + +- FB_TYPE_INTERLEAVED_PLANES + +Macropixels are split across multiple planes. The number of planes is equal to +the number of bits per macropixel, with plane i'th storing i'th bit from all +macropixels. + +Planes are interleaved in memory. The interleave factor, defined as the +distance in bytes between the beginning of two consecutive interleaved blocks +belonging to different planes, is stored in the fixed screen information +type_aux field. + +- FB_TYPE_FOURCC + +Macropixels are stored in memory as described by the format FOURCC identifier +stored in the variable screen information grayscale field. + +- FB_VISUAL_MONO01 + +Pixels are black or white and stored on a number of bits (typically one) +specified by the variable screen information bpp field. + +Black pixels are represented by all bits set to 1 and white pixels by all bits +set to 0. When the number of bits per pixel is smaller than 8, several pixels +are packed together in a byte. + +FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only. + +- FB_VISUAL_MONO10 + +Pixels are black or white and stored on a number of bits (typically one) +specified by the variable screen information bpp field. + +Black pixels are represented by all bits set to 0 and white pixels by all bits +set to 1. When the number of bits per pixel is smaller than 8, several pixels +are packed together in a byte. + +FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only. + +- FB_VISUAL_TRUECOLOR + +Pixels are broken into red, green and blue components, and each component +indexes a read-only lookup table for the corresponding value. Lookup tables +are device-dependent, and provide linear or non-linear ramps. + +Each component is stored in a macropixel according to the variable screen +information red, green, blue and transp fields. + +- FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR + +Pixel values are encoded as indices into a colormap that stores red, green and +blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR +and read-write for FB_VISUAL_PSEUDOCOLOR. + +Each pixel value is stored in the number of bits reported by the variable +screen information bits_per_pixel field. + +- FB_VISUAL_DIRECTCOLOR + +Pixels are broken into red, green and blue components, and each component +indexes a programmable lookup table for the corresponding value. + +Each component is stored in a macropixel according to the variable screen +information red, green, blue and transp fields. + +- FB_VISUAL_FOURCC + +Pixels are encoded and interpreted as described by the format FOURCC +identifier stored in the variable screen information grayscale field. + + +3. Screen information +--------------------- + +Screen information are queried by applications using the FBIOGET_FSCREENINFO +and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a +fb_fix_screeninfo and fb_var_screeninfo structure respectively. + +struct fb_fix_screeninfo stores device independent unchangeable information +about the frame buffer device and the current format. Those information can't +be directly modified by applications, but can be changed by the driver when an +application modifies the format:: + + struct fb_fix_screeninfo { + char id[16]; /* identification string eg "TT Builtin" */ + unsigned long smem_start; /* Start of frame buffer mem */ + /* (physical address) */ + __u32 smem_len; /* Length of frame buffer mem */ + __u32 type; /* see FB_TYPE_* */ + __u32 type_aux; /* Interleave for interleaved Planes */ + __u32 visual; /* see FB_VISUAL_* */ + __u16 xpanstep; /* zero if no hardware panning */ + __u16 ypanstep; /* zero if no hardware panning */ + __u16 ywrapstep; /* zero if no hardware ywrap */ + __u32 line_length; /* length of a line in bytes */ + unsigned long mmio_start; /* Start of Memory Mapped I/O */ + /* (physical address) */ + __u32 mmio_len; /* Length of Memory Mapped I/O */ + __u32 accel; /* Indicate to driver which */ + /* specific chip/card we have */ + __u16 capabilities; /* see FB_CAP_* */ + __u16 reserved[2]; /* Reserved for future compatibility */ + }; + +struct fb_var_screeninfo stores device independent changeable information +about a frame buffer device, its current format and video mode, as well as +other miscellaneous parameters:: + + struct fb_var_screeninfo { + __u32 xres; /* visible resolution */ + __u32 yres; + __u32 xres_virtual; /* virtual resolution */ + __u32 yres_virtual; + __u32 xoffset; /* offset from virtual to visible */ + __u32 yoffset; /* resolution */ + + __u32 bits_per_pixel; /* guess what */ + __u32 grayscale; /* 0 = color, 1 = grayscale, */ + /* >1 = FOURCC */ + struct fb_bitfield red; /* bitfield in fb mem if true color, */ + struct fb_bitfield green; /* else only length is significant */ + struct fb_bitfield blue; + struct fb_bitfield transp; /* transparency */ + + __u32 nonstd; /* != 0 Non standard pixel format */ + + __u32 activate; /* see FB_ACTIVATE_* */ + + __u32 height; /* height of picture in mm */ + __u32 width; /* width of picture in mm */ + + __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */ + + /* Timing: All values in pixclocks, except pixclock (of course) */ + __u32 pixclock; /* pixel clock in ps (pico seconds) */ + __u32 left_margin; /* time from sync to picture */ + __u32 right_margin; /* time from picture to sync */ + __u32 upper_margin; /* time from sync to picture */ + __u32 lower_margin; + __u32 hsync_len; /* length of horizontal sync */ + __u32 vsync_len; /* length of vertical sync */ + __u32 sync; /* see FB_SYNC_* */ + __u32 vmode; /* see FB_VMODE_* */ + __u32 rotate; /* angle we rotate counter clockwise */ + __u32 colorspace; /* colorspace for FOURCC-based modes */ + __u32 reserved[4]; /* Reserved for future compatibility */ + }; + +To modify variable information, applications call the FBIOPUT_VSCREENINFO +ioctl with a pointer to a fb_var_screeninfo structure. If the call is +successful, the driver will update the fixed screen information accordingly. + +Instead of filling the complete fb_var_screeninfo structure manually, +applications should call the FBIOGET_VSCREENINFO ioctl and modify only the +fields they care about. + + +4. Format configuration +----------------------- + +Frame buffer devices offer two ways to configure the frame buffer format: the +legacy API and the FOURCC-based API. + + +The legacy API has been the only frame buffer format configuration API for a +long time and is thus widely used by application. It is the recommended API +for applications when using RGB and grayscale formats, as well as legacy +non-standard formats. + +To select a format, applications set the fb_var_screeninfo bits_per_pixel field +to the desired frame buffer depth. Values up to 8 will usually map to +monochrome, grayscale or pseudocolor visuals, although this is not required. + +- For grayscale formats, applications set the grayscale field to one. The red, + blue, green and transp fields must be set to 0 by applications and ignored by + drivers. Drivers must fill the red, blue and green offsets to 0 and lengths + to the bits_per_pixel value. + +- For pseudocolor formats, applications set the grayscale field to zero. The + red, blue, green and transp fields must be set to 0 by applications and + ignored by drivers. Drivers must fill the red, blue and green offsets to 0 + and lengths to the bits_per_pixel value. + +- For truecolor and directcolor formats, applications set the grayscale field + to zero, and the red, blue, green and transp fields to describe the layout of + color components in memory:: + + struct fb_bitfield { + __u32 offset; /* beginning of bitfield */ + __u32 length; /* length of bitfield */ + __u32 msb_right; /* != 0 : Most significant bit is */ + /* right */ + }; + + Pixel values are bits_per_pixel wide and are split in non-overlapping red, + green, blue and alpha (transparency) components. Location and size of each + component in the pixel value are described by the fb_bitfield offset and + length fields. Offset are computed from the right. + + Pixels are always stored in an integer number of bytes. If the number of + bits per pixel is not a multiple of 8, pixel values are padded to the next + multiple of 8 bits. + +Upon successful format configuration, drivers update the fb_fix_screeninfo +type, visual and line_length fields depending on the selected format. + + +The FOURCC-based API replaces format descriptions by four character codes +(FOURCC). FOURCCs are abstract identifiers that uniquely define a format +without explicitly describing it. This is the only API that supports YUV +formats. Drivers are also encouraged to implement the FOURCC-based API for RGB +and grayscale formats. + +Drivers that support the FOURCC-based API report this capability by setting +the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field. + +FOURCC definitions are located in the linux/videodev2.h header. However, and +despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2 +and don't require usage of the V4L2 subsystem. FOURCC documentation is +available in Documentation/userspace-api/media/v4l/pixfmt.rst. + +To select a format, applications set the grayscale field to the desired FOURCC. +For YUV formats, they should also select the appropriate colorspace by setting +the colorspace field to one of the colorspaces listed in linux/videodev2.h and +documented in Documentation/userspace-api/media/v4l/colorspaces.rst. + +The red, green, blue and transp fields are not used with the FOURCC-based API. +For forward compatibility reasons applications must zero those fields, and +drivers must ignore them. Values other than 0 may get a meaning in future +extensions. + +Upon successful format configuration, drivers update the fb_fix_screeninfo +type, visual and line_length fields depending on the selected format. The type +and visual fields are set to FB_TYPE_FOURCC and FB_VISUAL_FOURCC respectively. diff --git a/Documentation/fb/arkfb.rst b/Documentation/fb/arkfb.rst new file mode 100644 index 000000000..aeca8773d --- /dev/null +++ b/Documentation/fb/arkfb.rst @@ -0,0 +1,68 @@ +======================================== +arkfb - fbdev driver for ARK Logic chips +======================================== + + +Supported Hardware +================== + + ARK 2000PV chip + ICS 5342 ramdac + + - only BIOS initialized VGA devices supported + - probably not working on big endian + + +Supported Features +================== + + * 4 bpp pseudocolor modes (with 18bit palette, two variants) + * 8 bpp pseudocolor mode (with 18bit palette) + * 16 bpp truecolor modes (RGB 555 and RGB 565) + * 24 bpp truecolor mode (RGB 888) + * 32 bpp truecolor mode (RGB 888) + * text mode (activated by bpp = 0) + * doublescan mode variant (not available in text mode) + * panning in both directions + * suspend/resume support + +Text mode is supported even in higher resolutions, but there is limitation to +lower pixclocks (i got maximum about 70 MHz, it is dependent on specific +hardware). This limitation is not enforced by driver. Text mode supports 8bit +wide fonts only (hardware limitation) and 16bit tall fonts (driver +limitation). Unfortunately character attributes (like color) in text mode are +broken for unknown reason, so its usefulness is limited. + +There are two 4 bpp modes. First mode (selected if nonstd == 0) is mode with +packed pixels, high nibble first. Second mode (selected if nonstd == 1) is mode +with interleaved planes (1 byte interleave), MSB first. Both modes support +8bit wide fonts only (driver limitation). + +Suspend/resume works on systems that initialize video card during resume and +if device is active (for example used by fbcon). + + +Missing Features +================ +(alias TODO list) + + * secondary (not initialized by BIOS) device support + * big endian support + * DPMS support + * MMIO support + * interlaced mode variant + * support for fontwidths != 8 in 4 bpp modes + * support for fontheight != 16 in text mode + * hardware cursor + * vsync synchronization + * feature connector support + * acceleration support (8514-like 2D) + + +Known bugs +========== + + * character attributes (and cursor) in text mode are broken + +-- +Ondrej Zajicek diff --git a/Documentation/fb/aty128fb.rst b/Documentation/fb/aty128fb.rst new file mode 100644 index 000000000..0da8070a5 --- /dev/null +++ b/Documentation/fb/aty128fb.rst @@ -0,0 +1,73 @@ +========================================= +aty128fb - ATI Rage128 framebuffer driver +========================================= + +This is a driver for a graphic framebuffer for ATI Rage128 based devices +on Intel and PPC boxes. + +Advantages: + + * It provides a nice large console (128 cols + 48 lines with 1024x768) + without using tiny, unreadable fonts. + * You can run XF68_FBDev on top of /dev/fb0 + * Most important: boot logo :-) + +Disadvantages: + + * graphic mode is slower than text mode... but you should not notice + if you use same resolution as you used in textmode. + * still experimental. + + +How to use it? +============== + +Switching modes is done using the video=aty128fb:... modedb +boot parameter or using `fbset` program. + +See Documentation/fb/modedb.rst for more information on modedb +resolutions. + +You should compile in both vgacon (to boot if you remove your Rage128 from +box) and aty128fb (for graphics mode). You should not compile-in vesafb +unless you have primary display on non-Rage128 VBE2.0 device (see +Documentation/fb/vesafb.rst for details). + + +X11 +=== + +XF68_FBDev should generally work fine, but it is non-accelerated. As of +this document, 8 and 32bpp works fine. There have been palette issues +when switching from X to console and back to X. You will have to restart +X to fix this. + + +Configuration +============= + +You can pass kernel command line options to vesafb with +`video=aty128fb:option1,option2:value2,option3` (multiple options should +be separated by comma, values are separated from options by `:`). +Accepted options: + +========= ======================================================= +noaccel do not use acceleration engine. It is default. +accel use acceleration engine. Not finished. +vmode:x chooses PowerMacintosh video mode . Deprecated. +cmode:x chooses PowerMacintosh colour mode . Deprecated. + selects startup videomode. See modedb.txt for detailed + explanation. Default is 640x480x8bpp. +========= ======================================================= + + +Limitations +=========== + +There are known and unknown bugs, features and misfeatures. +Currently there are following known bugs: + + - This driver is still experimental and is not finished. Too many + bugs/errata to list here. + +Brad Douglas diff --git a/Documentation/fb/cirrusfb.rst b/Documentation/fb/cirrusfb.rst new file mode 100644 index 000000000..8c3e6c6cb --- /dev/null +++ b/Documentation/fb/cirrusfb.rst @@ -0,0 +1,94 @@ +============================================ +Framebuffer driver for Cirrus Logic chipsets +============================================ + +Copyright 1999 Jeff Garzik + + +.. just a little something to get people going; contributors welcome! + + +Chip families supported: + - SD64 + - Piccolo + - Picasso + - Spectrum + - Alpine (GD-543x/4x) + - Picasso4 (GD-5446) + - GD-5480 + - Laguna (GD-546x) + +Bus's supported: + - PCI + - Zorro + +Architectures supported: + - i386 + - Alpha + - PPC (Motorola Powerstack) + - m68k (Amiga) + + + +Default video modes +------------------- +At the moment, there are two kernel command line arguments supported: + +- mode:640x480 +- mode:800x600 +- mode:1024x768 + +Full support for startup video modes (modedb) will be integrated soon. + +Version 1.9.9.1 +--------------- +* Fix memory detection for 512kB case +* 800x600 mode +* Fixed timings +* Hint for AXP: Use -accel false -vyres -1 when changing resolution + + +Version 1.9.4.4 +--------------- +* Preliminary Laguna support +* Overhaul color register routines. +* Associated with the above, console colors are now obtained from a LUT + called 'palette' instead of from the VGA registers. This code was + modelled after that in atyfb and matroxfb. +* Code cleanup, add comments. +* Overhaul SR07 handling. +* Bug fixes. + + +Version 1.9.4.3 +--------------- +* Correctly set default startup video mode. +* Do not override ram size setting. Define + CLGEN_USE_HARDCODED_RAM_SETTINGS if you _do_ want to override the RAM + setting. +* Compile fixes related to new 2.3.x IORESOURCE_IO[PORT] symbol changes. +* Use new 2.3.x resource allocation. +* Some code cleanup. + + +Version 1.9.4.2 +--------------- +* Casting fixes. +* Assertions no longer cause an oops on purpose. +* Bug fixes. + + +Version 1.9.4.1 +--------------- +* Add compatibility support. Now requires a 2.1.x, 2.2.x or 2.3.x kernel. + + +Version 1.9.4 +------------- +* Several enhancements, smaller memory footprint, a few bugfixes. +* Requires kernel 2.3.14-pre1 or later. + + +Version 1.9.3 +------------- +* Bundled with kernel 2.3.14-pre1 or later. diff --git a/Documentation/fb/cmap_xfbdev.rst b/Documentation/fb/cmap_xfbdev.rst new file mode 100644 index 000000000..5db5e9787 --- /dev/null +++ b/Documentation/fb/cmap_xfbdev.rst @@ -0,0 +1,56 @@ +========================== +Understanding fbdev's cmap +========================== + +These notes explain how X's dix layer uses fbdev's cmap structures. + +- example of relevant structures in fbdev as used for a 3-bit grayscale cmap:: + + struct fb_var_screeninfo { + .bits_per_pixel = 8, + .grayscale = 1, + .red = { 4, 3, 0 }, + .green = { 0, 0, 0 }, + .blue = { 0, 0, 0 }, + } + struct fb_fix_screeninfo { + .visual = FB_VISUAL_STATIC_PSEUDOCOLOR, + } + for (i = 0; i < 8; i++) + info->cmap.red[i] = (((2*i)+1)*(0xFFFF))/16; + memcpy(info->cmap.green, info->cmap.red, sizeof(u16)*8); + memcpy(info->cmap.blue, info->cmap.red, sizeof(u16)*8); + +- X11 apps do something like the following when trying to use grayscale:: + + for (i=0; i < 8; i++) { + char colorspec[64]; + memset(colorspec,0,64); + sprintf(colorspec, "rgb:%x/%x/%x", i*36,i*36,i*36); + if (!XParseColor(outputDisplay, testColormap, colorspec, &wantedColor)) + printf("Can't get color %s\n",colorspec); + XAllocColor(outputDisplay, testColormap, &wantedColor); + grays[i] = wantedColor; + } + +There's also named equivalents like gray1..x provided you have an rgb.txt. + +Somewhere in X's callchain, this results in a call to X code that handles the +colormap. For example, Xfbdev hits the following: + +xc-011010/programs/Xserver/dix/colormap.c:: + + FindBestPixel(pentFirst, size, prgb, channel) + + dr = (long) pent->co.local.red - prgb->red; + dg = (long) pent->co.local.green - prgb->green; + db = (long) pent->co.local.blue - prgb->blue; + sq = dr * dr; + UnsignedToBigNum (sq, &sum); + BigNumAdd (&sum, &temp, &sum); + +co.local.red are entries that were brought in through FBIOGETCMAP which come +directly from the info->cmap.red that was listed above. The prgb is the rgb +that the app wants to match to. The above code is doing what looks like a least +squares matching function. That's why the cmap entries can't be set to the left +hand side boundaries of a color range. diff --git a/Documentation/fb/deferred_io.rst b/Documentation/fb/deferred_io.rst new file mode 100644 index 000000000..7fc1933b0 --- /dev/null +++ b/Documentation/fb/deferred_io.rst @@ -0,0 +1,79 @@ +=========== +Deferred IO +=========== + +Deferred IO is a way to delay and repurpose IO. It uses host memory as a +buffer and the MMU pagefault as a pretrigger for when to perform the device +IO. The following example may be a useful explanation of how one such setup +works: + +- userspace app like Xfbdev mmaps framebuffer +- deferred IO and driver sets up fault and page_mkwrite handlers +- userspace app tries to write to mmapped vaddress +- we get pagefault and reach fault handler +- fault handler finds and returns physical page +- we get page_mkwrite where we add this page to a list +- schedule a workqueue task to be run after a delay +- app continues writing to that page with no additional cost. this is + the key benefit. +- the workqueue task comes in and mkcleans the pages on the list, then + completes the work associated with updating the framebuffer. this is + the real work talking to the device. +- app tries to write to the address (that has now been mkcleaned) +- get pagefault and the above sequence occurs again + +As can be seen from above, one benefit is roughly to allow bursty framebuffer +writes to occur at minimum cost. Then after some time when hopefully things +have gone quiet, we go and really update the framebuffer which would be +a relatively more expensive operation. + +For some types of nonvolatile high latency displays, the desired image is +the final image rather than the intermediate stages which is why it's okay +to not update for each write that is occurring. + +It may be the case that this is useful in other scenarios as well. Paul Mundt +has mentioned a case where it is beneficial to use the page count to decide +whether to coalesce and issue SG DMA or to do memory bursts. + +Another one may be if one has a device framebuffer that is in an usual format, +say diagonally shifting RGB, this may then be a mechanism for you to allow +apps to pretend to have a normal framebuffer but reswizzle for the device +framebuffer at vsync time based on the touched pagelist. + +How to use it: (for applications) +--------------------------------- +No changes needed. mmap the framebuffer like normal and just use it. + +How to use it: (for fbdev drivers) +---------------------------------- +The following example may be helpful. + +1. Setup your structure. Eg:: + + static struct fb_deferred_io hecubafb_defio = { + .delay = HZ, + .deferred_io = hecubafb_dpy_deferred_io, + }; + +The delay is the minimum delay between when the page_mkwrite trigger occurs +and when the deferred_io callback is called. The deferred_io callback is +explained below. + +2. Setup your deferred IO callback. Eg:: + + static void hecubafb_dpy_deferred_io(struct fb_info *info, + struct list_head *pagelist) + +The deferred_io callback is where you would perform all your IO to the display +device. You receive the pagelist which is the list of pages that were written +to during the delay. You must not modify this list. This callback is called +from a workqueue. + +3. Call init:: + + info->fbdefio = &hecubafb_defio; + fb_deferred_io_init(info); + +4. Call cleanup:: + + fb_deferred_io_cleanup(info); diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst new file mode 100644 index 000000000..3d4aab406 --- /dev/null +++ b/Documentation/fb/efifb.rst @@ -0,0 +1,71 @@ +=================================== +efifb - Generic EFI platform driver +=================================== + +This is a generic EFI platform driver for systems with UEFI firmware. The +system must be booted via the EFI stub for this to be usable. efifb supports +both firmware with Graphics Output Protocol (GOP) displays as well as older +systems with only Universal Graphics Adapter (UGA) displays. + +Supported Hardware +================== + +- iMac 17"/20" +- Macbook +- Macbook Pro 15"/17" +- MacMini +- ARM/ARM64/X86 systems with UEFI firmware + +How to use it? +============== + +For UGA displays, efifb does not have any kind of autodetection of your +machine. + +You have to add the following kernel parameters in your elilo.conf:: + + Macbook : + video=efifb:macbook + MacMini : + video=efifb:mini + Macbook Pro 15", iMac 17" : + video=efifb:i17 + Macbook Pro 17", iMac 20" : + video=efifb:i20 + +For GOP displays, efifb can autodetect the display's resolution and framebuffer +address, so these should work out of the box without any special parameters. + +Accepted options: + +======= =========================================================== +nowc Don't map the framebuffer write combined. This can be used + to workaround side-effects and slowdowns on other CPU cores + when large amounts of console data are written. +======= =========================================================== + +Options for GOP displays: + +mode=n + The EFI stub will set the mode of the display to mode number n if + possible. + +x[-(rgb|bgr|)] + The EFI stub will search for a display mode that matches the specified + horizontal and vertical resolution, and optionally bit depth, and set + the mode of the display to it if one is found. The bit depth can either + "rgb" or "bgr" to match specifically those pixel formats, or a number + for a mode with matching bits per pixel. + +auto + The EFI stub will choose the mode with the highest resolution (product + of horizontal and vertical resolution). If there are multiple modes + with the highest resolution, it will choose one with the highest color + depth. + +list + The EFI stub will list out all the display modes that are available. A + specific mode can then be chosen using one of the above options for the + next boot. + +Edgar Hucek diff --git a/Documentation/fb/ep93xx-fb.rst b/Documentation/fb/ep93xx-fb.rst new file mode 100644 index 000000000..93b3494f5 --- /dev/null +++ b/Documentation/fb/ep93xx-fb.rst @@ -0,0 +1,136 @@ +================================ +Driver for EP93xx LCD controller +================================ + +The EP93xx LCD controller can drive both standard desktop monitors and +embedded LCD displays. If you have a standard desktop monitor then you +can use the standard Linux video mode database. In your board file:: + + static struct ep93xxfb_mach_info some_board_fb_info = { + .num_modes = EP93XXFB_USE_MODEDB, + .bpp = 16, + }; + +If you have an embedded LCD display then you need to define a video +mode for it as follows:: + + static struct fb_videomode some_board_video_modes[] = { + { + .name = "some_lcd_name", + /* Pixel clock, porches, etc */ + }, + }; + +Note that the pixel clock value is in pico-seconds. You can use the +KHZ2PICOS macro to convert the pixel clock value. Most other values +are in pixel clocks. See Documentation/fb/framebuffer.rst for further +details. + +The ep93xxfb_mach_info structure for your board should look like the +following:: + + static struct ep93xxfb_mach_info some_board_fb_info = { + .num_modes = ARRAY_SIZE(some_board_video_modes), + .modes = some_board_video_modes, + .default_mode = &some_board_video_modes[0], + .bpp = 16, + }; + +The framebuffer device can be registered by adding the following to +your board initialisation function:: + + ep93xx_register_fb(&some_board_fb_info); + +Video Attribute Flags +===================== + +The ep93xxfb_mach_info structure has a flags field which can be used +to configure the controller. The video attributes flags are fully +documented in section 7 of the EP93xx users' guide. The following +flags are available: + +=============================== ========================================== +EP93XXFB_PCLK_FALLING Clock data on the falling edge of the + pixel clock. The default is to clock + data on the rising edge. + +EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By + default the blank signal is active low. + +EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By + default the horizontal sync is active low. + +EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By + default the vertical sync is active high. +=============================== ========================================== + +The physical address of the framebuffer can be controlled using the +following flags: + +=============================== ====================================== +EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This + is the default setting. + +EP93XXFB_USE_SDCSN1 Use SDCSn[1] for the framebuffer. + +EP93XXFB_USE_SDCSN2 Use SDCSn[2] for the framebuffer. + +EP93XXFB_USE_SDCSN3 Use SDCSn[3] for the framebuffer. +=============================== ====================================== + +Platform callbacks +================== + +The EP93xx framebuffer driver supports three optional platform +callbacks: setup, teardown and blank. The setup and teardown functions +are called when the framebuffer driver is installed and removed +respectively. The blank function is called whenever the display is +blanked or unblanked. + +The setup and teardown devices pass the platform_device structure as +an argument. The fb_info and ep93xxfb_mach_info structures can be +obtained as follows:: + + static int some_board_fb_setup(struct platform_device *pdev) + { + struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data; + struct fb_info *fb_info = platform_get_drvdata(pdev); + + /* Board specific framebuffer setup */ + } + +Setting the video mode +====================== + +The video mode is set using the following syntax:: + + video=XRESxYRES[-BPP][@REFRESH] + +If the EP93xx video driver is built-in then the video mode is set on +the Linux kernel command line, for example:: + + video=ep93xx-fb:800x600-16@60 + +If the EP93xx video driver is built as a module then the video mode is +set when the module is installed:: + + modprobe ep93xx-fb video=320x240 + +Screenpage bug +============== + +At least on the EP9315 there is a silicon bug which causes bit 27 of +the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is +an unofficial errata for this bug at:: + + https://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2 + +By default the EP93xx framebuffer driver checks if the allocated physical +address has bit 27 set. If it does, then the memory is freed and an +error is returned. The check can be disabled by adding the following +option when loading the driver:: + + ep93xx-fb.check_screenpage_bug=0 + +In some cases it may be possible to reconfigure your SDRAM layout to +avoid this bug. See section 13 of the EP93xx users' guide for details. diff --git a/Documentation/fb/fbcon.rst b/Documentation/fb/fbcon.rst new file mode 100644 index 000000000..a98a5cb0b --- /dev/null +++ b/Documentation/fb/fbcon.rst @@ -0,0 +1,354 @@ +======================= +The Framebuffer Console +======================= + +The framebuffer console (fbcon), as its name implies, is a text +console running on top of the framebuffer device. It has the functionality of +any standard text console driver, such as the VGA console, with the added +features that can be attributed to the graphical nature of the framebuffer. + +In the x86 architecture, the framebuffer console is optional, and +some even treat it as a toy. For other architectures, it is the only available +display device, text or graphical. + +What are the features of fbcon? The framebuffer console supports +high resolutions, varying font types, display rotation, primitive multihead, +etc. Theoretically, multi-colored fonts, blending, aliasing, and any feature +made available by the underlying graphics card are also possible. + +A. Configuration +================ + +The framebuffer console can be enabled by using your favorite kernel +configuration tool. It is under Device Drivers->Graphics Support-> +Console display driver support->Framebuffer Console Support. +Select 'y' to compile support statically or 'm' for module support. The +module will be fbcon. + +In order for fbcon to activate, at least one framebuffer driver is +required, so choose from any of the numerous drivers available. For x86 +systems, they almost universally have VGA cards, so vga16fb and vesafb will +always be available. However, using a chipset-specific driver will give you +more speed and features, such as the ability to change the video mode +dynamically. + +To display the penguin logo, choose any logo available in Graphics +support->Bootup logo. + +Also, you will need to select at least one compiled-in font, but if +you don't do anything, the kernel configuration tool will select one for you, +usually an 8x16 font. + +.. admonition:: GOTCHA + + A common bug report is enabling the framebuffer without enabling the + framebuffer console. Depending on the driver, you may get a blanked or + garbled display, but the system still boots to completion. If you are + fortunate to have a driver that does not alter the graphics chip, then you + will still get a VGA console. + +B. Loading +========== + +Possible scenarios: + +1. Driver and fbcon are compiled statically + + Usually, fbcon will automatically take over your console. The notable + exception is vesafb. It needs to be explicitly activated with the + vga= boot option parameter. + +2. Driver is compiled statically, fbcon is compiled as a module + + Depending on the driver, you either get a standard console, or a + garbled display, as mentioned above. To get a framebuffer console, + do a 'modprobe fbcon'. + +3. Driver is compiled as a module, fbcon is compiled statically + + You get your standard console. Once the driver is loaded with + 'modprobe xxxfb', fbcon automatically takes over the console with + the possible exception of using the fbcon=map:n option. See below. + +4. Driver and fbcon are compiled as a module. + + You can load them in any order. Once both are loaded, fbcon will take + over the console. + +C. Boot options +=============== + + The framebuffer console has several, largely unknown, boot options + that can change its behavior. + +1. fbcon=font: + + Select the initial font to use. The value 'name' can be any of the + compiled-in fonts: 10x18, 6x10, 6x8, 7x14, Acorn8x8, MINI4x6, + PEARL8x8, ProFont6x11, SUN12x22, SUN8x16, TER16x32, VGA8x16, VGA8x8. + + Note, not all drivers can handle font with widths not divisible by 8, + such as vga16fb. + + +2. fbcon=map:<0123> + + This is an interesting option. It tells which driver gets mapped to + which console. The value '0123' is a sequence that gets repeated until + the total length is 64 which is the number of consoles available. In + the above example, it is expanded to 012301230123... and the mapping + will be:: + + tty | 1 2 3 4 5 6 7 8 9 ... + fb | 0 1 2 3 0 1 2 3 0 ... + + ('cat /proc/fb' should tell you what the fb numbers are) + + One side effect that may be useful is using a map value that exceeds + the number of loaded fb drivers. For example, if only one driver is + available, fb0, adding fbcon=map:1 tells fbcon not to take over the + console. + + Later on, when you want to map the console the to the framebuffer + device, you can use the con2fbmap utility. + +3. fbcon=vc:- + + This option tells fbcon to take over only a range of consoles as + specified by the values 'n1' and 'n2'. The rest of the consoles + outside the given range will still be controlled by the standard + console driver. + + .. note:: + For x86 machines, the standard console is the VGA console which + is typically located on the same video card. Thus, the consoles that + are controlled by the VGA console will be garbled. + +4. fbcon=rotate: + + This option changes the orientation angle of the console display. The + value 'n' accepts the following: + + - 0 - normal orientation (0 degree) + - 1 - clockwise orientation (90 degrees) + - 2 - upside down orientation (180 degrees) + - 3 - counterclockwise orientation (270 degrees) + + The angle can be changed anytime afterwards by 'echoing' the same + numbers to any one of the 2 attributes found in + /sys/class/graphics/fbcon: + + - rotate - rotate the display of the active console + - rotate_all - rotate the display of all consoles + + Console rotation will only become available if Framebuffer Console + Rotation support is compiled in your kernel. + + .. note:: + This is purely console rotation. Any other applications that + use the framebuffer will remain at their 'normal' orientation. + Actually, the underlying fb driver is totally ignorant of console + rotation. + +5. fbcon=margin: + + This option specifies the color of the margins. The margins are the + leftover area at the right and the bottom of the screen that are not + used by text. By default, this area will be black. The 'color' value + is an integer number that depends on the framebuffer driver being used. + +6. fbcon=nodefer + + If the kernel is compiled with deferred fbcon takeover support, normally + the framebuffer contents, left in place by the firmware/bootloader, will + be preserved until there actually is some text is output to the console. + This option causes fbcon to bind immediately to the fbdev device. + +7. fbcon=logo-pos: + + The only possible 'location' is 'center' (without quotes), and when + given, the bootup logo is moved from the default top-left corner + location to the center of the framebuffer. If more than one logo is + displayed due to multiple CPUs, the collected line of logos is moved + as a whole. + +8. fbcon=logo-count: + + The value 'n' overrides the number of bootup logos. 0 disables the + logo, and -1 gives the default which is the number of online CPUs. + +D. Attaching, Detaching and Unloading +===================================== + +Before going on to how to attach, detach and unload the framebuffer console, an +illustration of the dependencies may help. + +The console layer, as with most subsystems, needs a driver that interfaces with +the hardware. Thus, in a VGA console:: + + console ---> VGA driver ---> hardware. + +Assuming the VGA driver can be unloaded, one must first unbind the VGA driver +from the console layer before unloading the driver. The VGA driver cannot be +unloaded if it is still bound to the console layer. (See +Documentation/driver-api/console.rst for more information). + +This is more complicated in the case of the framebuffer console (fbcon), +because fbcon is an intermediate layer between the console and the drivers:: + + console ---> fbcon ---> fbdev drivers ---> hardware + +The fbdev drivers cannot be unloaded if bound to fbcon, and fbcon cannot +be unloaded if it's bound to the console layer. + +So to unload the fbdev drivers, one must first unbind fbcon from the console, +then unbind the fbdev drivers from fbcon. Fortunately, unbinding fbcon from +the console layer will automatically unbind framebuffer drivers from +fbcon. Thus, there is no need to explicitly unbind the fbdev drivers from +fbcon. + +So, how do we unbind fbcon from the console? Part of the answer is in +Documentation/driver-api/console.rst. To summarize: + +Echo a value to the bind file that represents the framebuffer console +driver. So assuming vtcon1 represents fbcon, then:: + + echo 1 > /sys/class/vtconsole/vtcon1/bind - attach framebuffer console to + console layer + echo 0 > /sys/class/vtconsole/vtcon1/bind - detach framebuffer console from + console layer + +If fbcon is detached from the console layer, your boot console driver (which is +usually VGA text mode) will take over. A few drivers (rivafb and i810fb) will +restore VGA text mode for you. With the rest, before detaching fbcon, you +must take a few additional steps to make sure that your VGA text mode is +restored properly. The following is one of the several methods that you can do: + +1. Download or install vbetool. This utility is included with most + distributions nowadays, and is usually part of the suspend/resume tool. + +2. In your kernel configuration, ensure that CONFIG_FRAMEBUFFER_CONSOLE is set + to 'y' or 'm'. Enable one or more of your favorite framebuffer drivers. + +3. Boot into text mode and as root run:: + + vbetool vbestate save > + + The above command saves the register contents of your graphics + hardware to . You need to do this step only once as + the state file can be reused. + +4. If fbcon is compiled as a module, load fbcon by doing:: + + modprobe fbcon + +5. Now to detach fbcon:: + + vbetool vbestate restore < && \ + echo 0 > /sys/class/vtconsole/vtcon1/bind + +6. That's it, you're back to VGA mode. And if you compiled fbcon as a module, + you can unload it by 'rmmod fbcon'. + +7. To reattach fbcon:: + + echo 1 > /sys/class/vtconsole/vtcon1/bind + +8. Once fbcon is unbound, all drivers registered to the system will also + become unbound. This means that fbcon and individual framebuffer drivers + can be unloaded or reloaded at will. Reloading the drivers or fbcon will + automatically bind the console, fbcon and the drivers together. Unloading + all the drivers without unloading fbcon will make it impossible for the + console to bind fbcon. + +Notes for vesafb users: +======================= + +Unfortunately, if your bootline includes a vga=xxx parameter that sets the +hardware in graphics mode, such as when loading vesafb, vgacon will not load. +Instead, vgacon will replace the default boot console with dummycon, and you +won't get any display after detaching fbcon. Your machine is still alive, so +you can reattach vesafb. However, to reattach vesafb, you need to do one of +the following: + +Variation 1: + + a. Before detaching fbcon, do:: + + vbetool vbemode save > # do once for each vesafb mode, + # the file can be reused + + b. Detach fbcon as in step 5. + + c. Attach fbcon:: + + vbetool vbestate restore < && \ + echo 1 > /sys/class/vtconsole/vtcon1/bind + +Variation 2: + + a. Before detaching fbcon, do:: + + echo > /sys/class/tty/console/bind + + vbetool vbemode get + + b. Take note of the mode number + + b. Detach fbcon as in step 5. + + c. Attach fbcon:: + + vbetool vbemode set && \ + echo 1 > /sys/class/vtconsole/vtcon1/bind + +Samples: +======== + +Here are 2 sample bash scripts that you can use to bind or unbind the +framebuffer console driver if you are on an X86 box:: + + #!/bin/bash + # Unbind fbcon + + # Change this to where your actual vgastate file is located + # Or Use VGASTATE=$1 to indicate the state file at runtime + VGASTATE=/tmp/vgastate + + # path to vbetool + VBETOOL=/usr/local/bin + + + for (( i = 0; i < 16; i++)) + do + if test -x /sys/class/vtconsole/vtcon$i; then + if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \ + = 1 ]; then + if test -x $VBETOOL/vbetool; then + echo Unbinding vtcon$i + $VBETOOL/vbetool vbestate restore < $VGASTATE + echo 0 > /sys/class/vtconsole/vtcon$i/bind + fi + fi + fi + done + +--------------------------------------------------------------------------- + +:: + + #!/bin/bash + # Bind fbcon + + for (( i = 0; i < 16; i++)) + do + if test -x /sys/class/vtconsole/vtcon$i; then + if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \ + = 1 ]; then + echo Unbinding vtcon$i + echo 1 > /sys/class/vtconsole/vtcon$i/bind + fi + fi + done + +Antonino Daplas diff --git a/Documentation/fb/framebuffer.rst b/Documentation/fb/framebuffer.rst new file mode 100644 index 000000000..7fe087310 --- /dev/null +++ b/Documentation/fb/framebuffer.rst @@ -0,0 +1,353 @@ +======================= +The Frame Buffer Device +======================= + +Last revised: May 10, 2001 + + +0. Introduction +--------------- + +The frame buffer device provides an abstraction for the graphics hardware. It +represents the frame buffer of some video hardware and allows application +software to access the graphics hardware through a well-defined interface, so +the software doesn't need to know anything about the low-level (hardware +register) stuff. + +The device is accessed through special device nodes, usually located in the +/dev directory, i.e. /dev/fb*. + + +1. User's View of /dev/fb* +-------------------------- + +From the user's point of view, the frame buffer device looks just like any +other device in /dev. It's a character device using major 29; the minor +specifies the frame buffer number. + +By convention, the following device nodes are used (numbers indicate the device +minor numbers):: + + 0 = /dev/fb0 First frame buffer + 1 = /dev/fb1 Second frame buffer + ... + 31 = /dev/fb31 32nd frame buffer + +For backwards compatibility, you may want to create the following symbolic +links:: + + /dev/fb0current -> fb0 + /dev/fb1current -> fb1 + +and so on... + +The frame buffer devices are also `normal` memory devices, this means, you can +read and write their contents. You can, for example, make a screen snapshot by:: + + cp /dev/fb0 myfile + +There also can be more than one frame buffer at a time, e.g. if you have a +graphics card in addition to the built-in hardware. The corresponding frame +buffer devices (/dev/fb0 and /dev/fb1 etc.) work independently. + +Application software that uses the frame buffer device (e.g. the X server) will +use /dev/fb0 by default (older software uses /dev/fb0current). You can specify +an alternative frame buffer device by setting the environment variable +$FRAMEBUFFER to the path name of a frame buffer device, e.g. (for sh/bash +users):: + + export FRAMEBUFFER=/dev/fb1 + +or (for csh users):: + + setenv FRAMEBUFFER /dev/fb1 + +After this the X server will use the second frame buffer. + + +2. Programmer's View of /dev/fb* +-------------------------------- + +As you already know, a frame buffer device is a memory device like /dev/mem and +it has the same features. You can read it, write it, seek to some location in +it and mmap() it (the main usage). The difference is just that the memory that +appears in the special file is not the whole memory, but the frame buffer of +some video hardware. + +/dev/fb* also allows several ioctls on it, by which lots of information about +the hardware can be queried and set. The color map handling works via ioctls, +too. Look into for more information on what ioctls exist and on +which data structures they work. Here's just a brief overview: + + - You can request unchangeable information about the hardware, like name, + organization of the screen memory (planes, packed pixels, ...) and address + and length of the screen memory. + + - You can request and change variable information about the hardware, like + visible and virtual geometry, depth, color map format, timing, and so on. + If you try to change that information, the driver maybe will round up some + values to meet the hardware's capabilities (or return EINVAL if that isn't + possible). + + - You can get and set parts of the color map. Communication is done with 16 + bits per color part (red, green, blue, transparency) to support all + existing hardware. The driver does all the computations needed to apply + it to the hardware (round it down to less bits, maybe throw away + transparency). + +All this hardware abstraction makes the implementation of application programs +easier and more portable. E.g. the X server works completely on /dev/fb* and +thus doesn't need to know, for example, how the color registers of the concrete +hardware are organized. XF68_FBDev is a general X server for bitmapped, +unaccelerated video hardware. The only thing that has to be built into +application programs is the screen organization (bitplanes or chunky pixels +etc.), because it works on the frame buffer image data directly. + +For the future it is planned that frame buffer drivers for graphics cards and +the like can be implemented as kernel modules that are loaded at runtime. Such +a driver just has to call register_framebuffer() and supply some functions. +Writing and distributing such drivers independently from the kernel will save +much trouble... + + +3. Frame Buffer Resolution Maintenance +-------------------------------------- + +Frame buffer resolutions are maintained using the utility `fbset`. It can +change the video mode properties of a frame buffer device. Its main usage is +to change the current video mode, e.g. during boot up in one of your `/etc/rc.*` +or `/etc/init.d/*` files. + +Fbset uses a video mode database stored in a configuration file, so you can +easily add your own modes and refer to them with a simple identifier. + + +4. The X Server +--------------- + +The X server (XF68_FBDev) is the most notable application program for the frame +buffer device. Starting with XFree86 release 3.2, the X server is part of +XFree86 and has 2 modes: + + - If the `Display` subsection for the `fbdev` driver in the /etc/XF86Config + file contains a:: + + Modes "default" + + line, the X server will use the scheme discussed above, i.e. it will start + up in the resolution determined by /dev/fb0 (or $FRAMEBUFFER, if set). You + still have to specify the color depth (using the Depth keyword) and virtual + resolution (using the Virtual keyword) though. This is the default for the + configuration file supplied with XFree86. It's the most simple + configuration, but it has some limitations. + + - Therefore it's also possible to specify resolutions in the /etc/XF86Config + file. This allows for on-the-fly resolution switching while retaining the + same virtual desktop size. The frame buffer device that's used is still + /dev/fb0current (or $FRAMEBUFFER), but the available resolutions are + defined by /etc/XF86Config now. The disadvantage is that you have to + specify the timings in a different format (but `fbset -x` may help). + +To tune a video mode, you can use fbset or xvidtune. Note that xvidtune doesn't +work 100% with XF68_FBDev: the reported clock values are always incorrect. + + +5. Video Mode Timings +--------------------- + +A monitor draws an image on the screen by using an electron beam (3 electron +beams for color models, 1 electron beam for monochrome monitors). The front of +the screen is covered by a pattern of colored phosphors (pixels). If a phosphor +is hit by an electron, it emits a photon and thus becomes visible. + +The electron beam draws horizontal lines (scanlines) from left to right, and +from the top to the bottom of the screen. By modifying the intensity of the +electron beam, pixels with various colors and intensities can be shown. + +After each scanline the electron beam has to move back to the left side of the +screen and to the next line: this is called the horizontal retrace. After the +whole screen (frame) was painted, the beam moves back to the upper left corner: +this is called the vertical retrace. During both the horizontal and vertical +retrace, the electron beam is turned off (blanked). + +The speed at which the electron beam paints the pixels is determined by the +dotclock in the graphics board. For a dotclock of e.g. 28.37516 MHz (millions +of cycles per second), each pixel is 35242 ps (picoseconds) long:: + + 1/(28.37516E6 Hz) = 35.242E-9 s + +If the screen resolution is 640x480, it will take:: + + 640*35.242E-9 s = 22.555E-6 s + +to paint the 640 (xres) pixels on one scanline. But the horizontal retrace +also takes time (e.g. 272 `pixels`), so a full scanline takes:: + + (640+272)*35.242E-9 s = 32.141E-6 s + +We'll say that the horizontal scanrate is about 31 kHz:: + + 1/(32.141E-6 s) = 31.113E3 Hz + +A full screen counts 480 (yres) lines, but we have to consider the vertical +retrace too (e.g. 49 `lines`). So a full screen will take:: + + (480+49)*32.141E-6 s = 17.002E-3 s + +The vertical scanrate is about 59 Hz:: + + 1/(17.002E-3 s) = 58.815 Hz + +This means the screen data is refreshed about 59 times per second. To have a +stable picture without visible flicker, VESA recommends a vertical scanrate of +at least 72 Hz. But the perceived flicker is very human dependent: some people +can use 50 Hz without any trouble, while I'll notice if it's less than 80 Hz. + +Since the monitor doesn't know when a new scanline starts, the graphics board +will supply a synchronization pulse (horizontal sync or hsync) for each +scanline. Similarly it supplies a synchronization pulse (vertical sync or +vsync) for each new frame. The position of the image on the screen is +influenced by the moments at which the synchronization pulses occur. + +The following picture summarizes all timings. The horizontal retrace time is +the sum of the left margin, the right margin and the hsync length, while the +vertical retrace time is the sum of the upper margin, the lower margin and the +vsync length:: + + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |upper_margin | | | + | | ↓ | | | + +----------###############################################----------+-------+ + | # ↑ # | | + | # | # | | + | # | # | | + | # | # | | + | left # | # right | hsync | + | margin # | xres # margin | len | + |<-------->#<---------------+--------------------------->#<-------->|<----->| + | # | # | | + | # | # | | + | # | # | | + | # |yres # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # ↓ # | | + +----------###############################################----------+-------+ + | | ↑ | | | + | | |lower_margin | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |vsync_len | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + +The frame buffer device expects all horizontal timings in number of dotclocks +(in picoseconds, 1E-12 s), and vertical timings in number of scanlines. + + +6. Converting XFree86 timing values info frame buffer device timings +-------------------------------------------------------------------- + +An XFree86 mode line consists of the following fields:: + + "800x600" 50 800 856 976 1040 600 637 643 666 + < name > DCF HR SH1 SH2 HFL VR SV1 SV2 VFL + +The frame buffer device uses the following fields: + + - pixclock: pixel clock in ps (pico seconds) + - left_margin: time from sync to picture + - right_margin: time from picture to sync + - upper_margin: time from sync to picture + - lower_margin: time from picture to sync + - hsync_len: length of horizontal sync + - vsync_len: length of vertical sync + +1) Pixelclock: + + xfree: in MHz + + fb: in picoseconds (ps) + + pixclock = 1000000 / DCF + +2) horizontal timings: + + left_margin = HFL - SH2 + + right_margin = SH1 - HR + + hsync_len = SH2 - SH1 + +3) vertical timings: + + upper_margin = VFL - SV2 + + lower_margin = SV1 - VR + + vsync_len = SV2 - SV1 + +Good examples for VESA timings can be found in the XFree86 source tree, +under "xc/programs/Xserver/hw/xfree86/doc/modeDB.txt". + + +7. References +------------- + +For more specific information about the frame buffer device and its +applications, please refer to the Linux-fbdev website: + + http://linux-fbdev.sourceforge.net/ + +and to the following documentation: + + - The manual pages for fbset: fbset(8), fb.modes(5) + - The manual pages for XFree86: XF68_FBDev(1), XF86Config(4/5) + - The mighty kernel sources: + + - linux/drivers/video/ + - linux/include/linux/fb.h + - linux/include/video/ + + + +8. Mailing list +--------------- + +There is a frame buffer device related mailing list at kernel.org: +linux-fbdev@vger.kernel.org. + +Point your web browser to http://sourceforge.net/projects/linux-fbdev/ for +subscription information and archive browsing. + + +9. Downloading +-------------- + +All necessary files can be found at + + ftp://ftp.uni-erlangen.de/pub/Linux/LOCAL/680x0/ + +and on its mirrors. + +The latest version of fbset can be found at + + http://www.linux-fbdev.org/ + + +10. Credits +----------- + +This readme was written by Geert Uytterhoeven, partly based on the original +`X-framebuffer.README` by Roman Hodek and Martin Schaller. Section 6 was +provided by Frank Neumann. + +The frame buffer device abstraction was designed by Martin Schaller. diff --git a/Documentation/fb/gxfb.rst b/Documentation/fb/gxfb.rst new file mode 100644 index 000000000..3fda48560 --- /dev/null +++ b/Documentation/fb/gxfb.rst @@ -0,0 +1,52 @@ +======================================= +gxfb - AMD Geode GX2 framebuffer driver +======================================= + +This is a graphics framebuffer driver for AMD Geode GX2 based processors. + +Advantages: + + * No need to use AMD's VSA code (or other VESA emulation layer) in the + BIOS. + * It provides a nice large console (128 cols + 48 lines with 1024x768) + without using tiny, unreadable fonts. + * You can run XF68_FBDev on top of /dev/fb0 + * Most important: boot logo :-) + +Disadvantages: + + * graphic mode is slower than text mode... + + +How to use it? +============== + +Switching modes is done using gxfb.mode_option=... boot +parameter or using `fbset` program. + +See Documentation/fb/modedb.rst for more information on modedb +resolutions. + + +X11 +=== + +XF68_FBDev should generally work fine, but it is non-accelerated. + + +Configuration +============= + +You can pass kernel command line options to gxfb with gxfb.