summaryrefslogtreecommitdiffstats
path: root/Documentation/fb/internals.rst
diff options
context:
space:
mode:
authorSven Schnelle <svens@linux.ibm.com>2026-09-09 11:29:53 +0200
committerMasami Hiramatsu (Google) <mhiramat@kernel.org>2026-09-10 08:43:35 +0900
commitd22c3e0088e85be8131f7a9283f759cdbb20726d (patch)
tree9668df2aa27b26f850d3ba5ba1287e443803675c /Documentation/fb/internals.rst
downloadlinux-stable-d22c3e0088e85be8131f7a9283f759cdbb20726d.tar.gz
linux-stable-d22c3e0088e85be8131f7a9283f759cdbb20726d.zip
selftests/ftrace: Fix unique symbol check in kprobe_non_uniq_symbol.tcgrafted
The current regex also matches symbols in modules, which makes the test fail on s390 where name_show is present only once in the kernel, but also multiple times in modules: 000001b1401cdc20 t name_show 000001b0c05e6c40 t name_show [mdev] 000001b0c0495f30 t name_show [i2c_core] Fix this by changing the regular expression to only match the function name. Link: https://lore.kernel.org/all/20260909092954.2200558-1-svens@linux.ibm.com/ Fixes: 03b80ff8023a ("selftests/ftrace: Add new test case which checks non unique symbol") Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'Documentation/fb/internals.rst')
-rw-r--r--Documentation/fb/internals.rst86
1 files changed, 86 insertions, 0 deletions
diff --git a/Documentation/fb/internals.rst b/Documentation/fb/internals.rst
new file mode 100644
index 000000000..696b50aa7
--- /dev/null
+++ b/Documentation/fb/internals.rst
@@ -0,0 +1,86 @@
+=============================
+Frame Buffer device internals
+=============================
+
+This is a first start for some documentation about frame buffer device
+internals.
+
+Authors:
+
+- Geert Uytterhoeven <geert@linux-m68k.org>, 21 July 1998
+- James Simmons <jsimmons@user.sf.net>, Nov 26 2002
+
+--------------------------------------------------------------------------------
+
+Structures used by the frame buffer device API
+==============================================
+
+The following structures play a role in the game of frame buffer devices. They
+are defined in <linux/fb.h>.
+
+1. Outside the kernel (user space)
+
+ - struct fb_fix_screeninfo
+
+ Device independent unchangeable information about a frame buffer device and
+ a specific video mode. This can be obtained using the FBIOGET_FSCREENINFO
+ ioctl.
+
+ - struct fb_var_screeninfo
+
+ Device independent changeable information about a frame buffer device and a
+ specific video mode. This can be obtained using the FBIOGET_VSCREENINFO
+ ioctl, and updated with the FBIOPUT_VSCREENINFO ioctl. If you want to pan
+ the screen only, you can use the FBIOPAN_DISPLAY ioctl.
+
+ - struct fb_cmap
+
+ Device independent colormap information. You can get and set the colormap
+ using the FBIOGETCMAP and FBIOPUTCMAP ioctls.
+
+
+2. Inside the kernel
+
+ - struct fb_info
+
+ Generic information, API and low level information about a specific frame
+ buffer device instance (slot number, board address, ...).
+
+ - struct `par`
+
+ Device dependent information that uniquely defines the video mode for this
+ particular piece of hardware.
+
+
+Visuals used by the frame buffer device API
+===========================================
+
+
+Monochrome (FB_VISUAL_MONO01 and FB_VISUAL_MONO10)
+--------------------------------------------------
+Each pixel is either black or white.
+
+
+Pseudo color (FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR)
+---------------------------------------------------------------------
+The whole pixel value is fed through a programmable lookup table that has one
+color (including red, green, and blue intensities) for each possible pixel
+value, and that color is displayed.
+
+
+True color (FB_VISUAL_TRUECOLOR)
+--------------------------------
+The pixel value is broken up into red, green, and blue fields.
+
+
+Direct color (FB_VISUAL_DIRECTCOLOR)
+------------------------------------
+The pixel value is broken up into red, green, and blue fields, each of which
+are looked up in separate red, green, and blue lookup tables.
+
+
+Grayscale displays
+------------------
+Grayscale and static grayscale are special variants of pseudo color and static
+pseudo color, where the red, green and blue components are always equal to
+each other.