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/modedb.rst | 182 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 182 insertions(+) create mode 100644 Documentation/fb/modedb.rst (limited to 'Documentation/fb/modedb.rst') diff --git a/Documentation/fb/modedb.rst b/Documentation/fb/modedb.rst new file mode 100644 index 000000000..bb2889c6e --- /dev/null +++ b/Documentation/fb/modedb.rst @@ -0,0 +1,182 @@ +================================= +modedb default video mode support +================================= + + +Currently all frame buffer device drivers have their own video mode databases, +which is a mess and a waste of resources. The main idea of modedb is to have + + - one routine to probe for video modes, which can be used by all frame buffer + devices + - one generic video mode database with a fair amount of standard videomodes + (taken from XFree86) + - the possibility to supply your own mode database for graphics hardware that + needs non-standard modes, like amifb and Mac frame buffer drivers (which + use macmodes.c) + +When a frame buffer device receives a video= option it doesn't know, it should +consider that to be a video mode option. If no frame buffer device is specified +in a video= option, fbmem considers that to be a global video mode option. + +Valid mode specifiers (mode_option argument):: + + x[M][R][-][@][i][m][eDd] + [-][@] + +with , , and decimal numbers and a string. +Things between square brackets are optional. + +Valid names are:: + + - NSTC: 480i output, with the CCIR System-M TV mode and NTSC color encoding + - NTSC-J: 480i output, with the CCIR System-M TV mode, the NTSC color + encoding, and a black level equal to the blanking level. + - PAL: 576i output, with the CCIR System-B TV mode and PAL color encoding + - PAL-M: 480i output, with the CCIR System-M TV mode and PAL color encoding + +If 'M' is specified in the mode_option argument (after and before + and , if specified) the timings will be calculated using +VESA(TM) Coordinated Video Timings instead of looking up the mode from a table. +If 'R' is specified, do a 'reduced blanking' calculation for digital displays. +If 'i' is specified, calculate for an interlaced mode. And if 'm' is +specified, add margins to the calculation (1.8% of xres rounded down to 8 +pixels and 1.8% of yres). + + Sample usage: 1024x768M@60m - CVT timing with margins + +DRM drivers also add options to enable or disable outputs: + +'e' will force the display to be enabled, i.e. it will override the detection +if a display is connected. 'D' will force the display to be enabled and use +digital output. This is useful for outputs that have both analog and digital +signals (e.g. HDMI and DVI-I). For other outputs it behaves like 'e'. If 'd' +is specified the output is disabled. + +You can additionally specify which output the options matches to. +To force the VGA output to be enabled and drive a specific mode say:: + + video=VGA-1:1280x1024@60me + +Specifying the option multiple times for different ports is possible, e.g.:: + + video=LVDS-1:d video=HDMI-1:D + +Options can also be passed after the mode, using commas as separator. + + Sample usage: 720x480,rotate=180 - 720x480 mode, rotated by 180 degrees + +Valid options are:: + + - margin_top, margin_bottom, margin_left, margin_right (integer): + Number of pixels in the margins, typically to deal with overscan on TVs + - reflect_x (boolean): Perform an axial symmetry on the X axis + - reflect_y (boolean): Perform an axial symmetry on the Y axis + - rotate (integer): Rotate the initial framebuffer by x + degrees. Valid values are 0, 90, 180 and 270. + - tv_mode: Analog TV mode. One of "NTSC", "NTSC-443", "NTSC-J", "PAL", + "PAL-M", "PAL-N", or "SECAM". + - panel_orientation, one of "normal", "upside_down", "left_side_up", or + "right_side_up". For KMS drivers only, this sets the "panel orientation" + property on the kms connector as hint for kms users. + + +----------------------------------------------------------------------------- + +What is the VESA(TM) Coordinated Video Timings (CVT)? +===================================================== + +From the VESA(TM) Website: + + "The purpose of CVT is to provide a method for generating a consistent + and coordinated set of standard formats, display refresh rates, and + timing specifications for computer display products, both those + employing CRTs, and those using other display technologies. The + intention of CVT is to give both source and display manufacturers a + common set of tools to enable new timings to be developed in a + consistent manner that ensures greater compatibility." + +This is the third standard approved by VESA(TM) concerning video timings. The +first was the Discrete Video Timings (DVT) which is a collection of +pre-defined modes approved by VESA(TM). The second is the Generalized Timing +Formula (GTF) which is an algorithm to calculate the timings, given the +pixelclock, the horizontal sync frequency, or the vertical refresh rate. + +The GTF is limited by the fact that it is designed mainly for CRT displays. +It artificially increases the pixelclock because of its high blanking +requirement. This is inappropriate for digital display interface with its high +data rate which requires that it conserves the pixelclock as much as possible. +Also, GTF does not take into account the aspect ratio of the display. + +The CVT addresses these limitations. If used with CRT's, the formula used +is a derivation of GTF with a few modifications. If used with digital +displays, the "reduced blanking" calculation can be used. + +From the framebuffer subsystem perspective, new formats need not be added +to the global mode database whenever a new mode is released by display +manufacturers. Specifying for CVT will work for most, if not all, relatively +new CRT displays and probably with most flatpanels, if 'reduced blanking' +calculation is specified. (The CVT compatibility of the display can be +determined from its EDID. The version 1.3 of the EDID has extra 128-byte +blocks where additional timing information is placed. As of this time, there +is no support yet in the layer to parse this additional blocks.) + +CVT also introduced a new naming convention (should be seen from dmesg output):: + + M[-R] + + where: pix = total amount of pixels in MB (xres x yres) + M = always present + a = aspect ratio (3 - 4:3; 4 - 5:4; 9 - 15:9, 16:9; A - 16:10) + -R = reduced blanking + + example: .48M3-R - 800x600 with reduced blanking + +Note: VESA(TM) has restrictions on what is a standard CVT timing: + + - aspect ratio can only be one of the above values + - acceptable refresh rates are 50, 60, 70 or 85 Hz only + - if reduced blanking, the refresh rate must be at 60Hz + +If one of the above are not satisfied, the kernel will print a warning but the +timings will still be calculated. + +----------------------------------------------------------------------------- + +To find a suitable video mode, you just call:: + + int __init fb_find_mode(struct fb_var_screeninfo *var, + struct fb_info *info, const char *mode_option, + const struct fb_videomode *db, unsigned int dbsize, + const struct fb_videomode *default_mode, + unsigned int default_bpp) + +with db/dbsize your non-standard video mode database, or NULL to use the +standard video mode database. + +fb_find_mode() first tries the specified video mode (or any mode that matches, +e.g. there can be multiple 640x480 modes, each of them is tried). If that +fails, the default mode is tried. If that fails, it walks over all modes. + +To specify a video mode at bootup, use the following boot options:: + + video=:x[-][@refresh] + +where is a name from the table below. Valid default modes can be +found in drivers/video/fbdev/core/modedb.c. Check your driver's documentation. +There may be more modes:: + + Drivers that support modedb boot options + Boot Name Cards Supported + + amifb - Amiga chipset frame buffer + aty128fb - ATI Rage128 / Pro frame buffer + atyfb - ATI Mach64 frame buffer + pm2fb - Permedia 2/2V frame buffer + pm3fb - Permedia 3 frame buffer + sstfb - Voodoo 1/2 (SST1) chipset frame buffer + tdfxfb - 3D Fx frame buffer + tridentfb - Trident (Cyber)blade chipset frame buffer + vt8623fb - VIA 8623 frame buffer + +BTW, only a few fb drivers use this at the moment. Others are to follow +(feel free to send patches). The DRM drivers also support this. -- cgit v1.3.1