Documentation/fb/api.rst

9 ---------------
12 with frame buffer devices. In-kernel APIs between device drivers and the frame
22 ---------------
36 - FB_CAP_FOURCC
38 The driver supports the four character code (FOURCC) based format setting API.
44 --------------------
46 Pixels are stored in memory in hardware-dependent formats. Applications need
47 to be aware of the pixel storage format in order to write image data to the
48 frame buffer memory in the format expected by the hardware.
58 - FB_TYPE_PACKED_PIXELS
67 - FB_TYPE_PLANES
75 - FB_TYPE_INTERLEAVED_PLANES
86 - FB_TYPE_FOURCC
88 Macropixels are stored in memory as described by the format FOURCC identifier
91 - FB_VISUAL_MONO01
97 set to 0. When the number of bits per pixel is smaller than 8, several pixels
102 - FB_VISUAL_MONO10
108 set to 1. When the number of bits per pixel is smaller than 8, several pixels
113 - FB_VISUAL_TRUECOLOR
116 indexes a read-only lookup table for the corresponding value. Lookup tables
117 are device-dependent, and provide linear or non-linear ramps.
122 - FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR
124 Pixel values are encoded as indices into a colormap that stores red, green and
125 blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
126 and read-write for FB_VISUAL_PSEUDOCOLOR.
128 Each pixel value is stored in the number of bits reported by the variable
131 - FB_VISUAL_DIRECTCOLOR
139 - FB_VISUAL_FOURCC
141 Pixels are encoded and  interpreted as described by the format FOURCC
146 ---------------------
153 about the frame buffer device and the current format. Those information can't
155 application modifies the format::
179 about a frame buffer device, its current format and video mode, as well as
198 	__u32 nonstd;			/* != 0 Non standard pixel format */
208 	__u32 pixclock;			/* pixel clock in ps (pico seconds) */
218 	__u32 colorspace;		/* colorspace for FOURCC-based modes */
231 4. Format configuration
232 -----------------------
234 Frame buffer devices offer two ways to configure the frame buffer format: the
235 legacy API and the FOURCC-based API.
238 The legacy API has been the only frame buffer format configuration API for a
241 non-standard formats.
243 To select a format, applications set the fb_var_screeninfo bits_per_pixel field
247 - For grayscale formats, applications set the grayscale field to one. The red,
252 - For pseudocolor formats, applications set the grayscale field to zero. The
257 - For truecolor and directcolor formats, applications set the grayscale field
268   Pixel values are bits_per_pixel wide and are split in non-overlapping red,
270   component in the pixel value are described by the fb_bitfield offset and
274   bits per pixel is not a multiple of 8, pixel values are padded to the next
277 Upon successful format configuration, drivers update the fb_fix_screeninfo
278 type, visual and line_length fields depending on the selected format.
281 The FOURCC-based API replaces format descriptions by four character codes
282 (FOURCC). FOURCCs are abstract identifiers that uniquely define a format
284 formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
287 Drivers that support the FOURCC-based API report this capability by setting
293 available in Documentation/userspace-api/media/v4l/pixfmt.rst.
295 To select a format, applications set the grayscale field to the desired FOURCC.
298 documented in Documentation/userspace-api/media/v4l/colorspaces.rst.
300 The red, green, blue and transp fields are not used with the FOURCC-based API.
305 Upon successful format configuration, drivers update the fb_fix_screeninfo
306 type, visual and line_length fields depending on the selected format. The type