patch-2.1.107 linux/Documentation/fb/internals.txt

• Lines: 87
• Date: Wed Jun 24 14:44:00 1998
• Orig file: v2.1.106/linux/Documentation/fb/internals.txt
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.106/linux/Documentation/fb/internals.txt linux/Documentation/fb/internals.txt
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+
+This is a first start for some documentation about frame buffer device
+internals.
+
+Geert Uytterhoeven <Geert.Uytterhoeven@cs.kuleuven.ac.be>, 10 June 1998
+
+--------------------------------------------------------------------------------
+
+	    ***  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.
+
+  - struct display
+
+    Interface between the frame buffer device and the console driver.
+
+
+--------------------------------------------------------------------------------
+
+	    ***  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, each of which 
+are looked up in separate red, green, and blue lookup tables.
+
+
+Direct color (FB_VISUAL_DIRECTCOLOR)
+------------------------------------
+The pixel value is broken up into red, green, and blue fields. This is what
+most people mean when then say `true color'.
+
+
+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.
+