Documentation/fb/api.txt

1 			The Frame Buffer Device API
2 			---------------------------
8 ---------------
10 This document describes the frame buffer API used by applications to interact
11 with frame buffer devices. In-kernel APIs between device drivers and the frame
12 buffer core are not described.
14 Due to a lack of documentation in the original frame buffer API, drivers
21 ---------------
35 - FB_CAP_FOURCC
43 --------------------
45 Pixels are stored in memory in hardware-dependent formats. Applications need
47 frame buffer memory in the format expected by the hardware.
49 Formats are described by frame buffer types and visuals. Some visuals require
57 - FB_TYPE_PACKED_PIXELS
66 - FB_TYPE_PLANES
74 - FB_TYPE_INTERLEAVED_PLANES
85 - FB_TYPE_FOURCC
90 - FB_VISUAL_MONO01
101 - FB_VISUAL_MONO10
112 - FB_VISUAL_TRUECOLOR
115 indexes a read-only lookup table for the corresponding value. Lookup tables
116 are device-dependent, and provide linear or non-linear ramps.
121 - FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR
124 blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
125 and read-write for FB_VISUAL_PSEUDOCOLOR.
130 - FB_VISUAL_DIRECTCOLOR
138 - FB_VISUAL_FOURCC
145 ---------------------
152 about the frame buffer device and the current format. Those information can't
158 	unsigned long smem_start;	/* Start of frame buffer mem */
160 	__u32 smem_len;			/* Length of frame buffer mem */
178 about a frame buffer device, its current format and video mode, as well as
217 	__u32 colorspace;		/* colorspace for FOURCC-based modes */
231 -----------------------
233 Frame buffer devices offer two ways to configure the frame buffer format: the
234 legacy API and the FOURCC-based API.
237 The legacy API has been the only frame buffer format configuration API for a
240 non-standard formats.
243 to the desired frame buffer depth. Values up to 8 will usually map to
246 - For grayscale formats, applications set the grayscale field to one. The red,
251 - For pseudocolor formats, applications set the grayscale field to zero. The
256 - For truecolor and directcolor formats, applications set the grayscale field
267   Pixel values are bits_per_pixel wide and are split in non-overlapping red,
280 The FOURCC-based API replaces format descriptions by four character codes
283 formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
286 Drivers that support the FOURCC-based API report this capability by setting
299 The red, green, blue and transp fields are not used with the FOURCC-based API.