mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
synced 2025-10-31 08:26:29 +00:00
1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
83 lines
2.6 KiB
Plaintext
83 lines
2.6 KiB
Plaintext
|
|
This is a first start for some documentation about frame buffer device
|
|
internals.
|
|
|
|
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.
|
|
|