^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) ===========================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) The Frame Buffer Device API
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ===========================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) Last revised: June 21, 2011
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) 0. Introduction
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) ---------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) This document describes the frame buffer API used by applications to interact
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) with frame buffer devices. In-kernel APIs between device drivers and the frame
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) buffer core are not described.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) Due to a lack of documentation in the original frame buffer API, drivers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) behaviours differ in subtle (and not so subtle) ways. This document describes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) the recommended API implementation, but applications should be prepared to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) deal with different behaviours.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 1. Capabilities
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) ---------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) Device and driver capabilities are reported in the fixed screen information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) capabilities field::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) struct fb_fix_screeninfo {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) __u16 capabilities; /* see FB_CAP_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Application should use those capabilities to find out what features they can
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) expect from the device and driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) - FB_CAP_FOURCC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) The driver supports the four character code (FOURCC) based format setting API.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) When supported, formats are configured using a FOURCC instead of manually
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) specifying color components layout.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) 2. Types and visuals
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) --------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) Pixels are stored in memory in hardware-dependent formats. Applications need
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) to be aware of the pixel storage format in order to write image data to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) frame buffer memory in the format expected by the hardware.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) Formats are described by frame buffer types and visuals. Some visuals require
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) additional information, which are stored in the variable screen information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) bits_per_pixel, grayscale, red, green, blue and transp fields.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) Visuals describe how color information is encoded and assembled to create
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) macropixels. Types describe how macropixels are stored in memory. The following
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) types and visuals are supported.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) - FB_TYPE_PACKED_PIXELS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) Macropixels are stored contiguously in a single plane. If the number of bits
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) per macropixel is not a multiple of 8, whether macropixels are padded to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) next multiple of 8 bits or packed together into bytes depends on the visual.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) Padding at end of lines may be present and is then reported through the fixed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) screen information line_length field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) - FB_TYPE_PLANES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) Macropixels are split across multiple planes. The number of planes is equal to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) the number of bits per macropixel, with plane i'th storing i'th bit from all
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) macropixels.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) Planes are located contiguously in memory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) - FB_TYPE_INTERLEAVED_PLANES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) Macropixels are split across multiple planes. The number of planes is equal to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) the number of bits per macropixel, with plane i'th storing i'th bit from all
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) macropixels.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) Planes are interleaved in memory. The interleave factor, defined as the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) distance in bytes between the beginning of two consecutive interleaved blocks
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) belonging to different planes, is stored in the fixed screen information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) type_aux field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) - FB_TYPE_FOURCC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) Macropixels are stored in memory as described by the format FOURCC identifier
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) stored in the variable screen information grayscale field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) - FB_VISUAL_MONO01
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) Pixels are black or white and stored on a number of bits (typically one)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) specified by the variable screen information bpp field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) Black pixels are represented by all bits set to 1 and white pixels by all bits
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) set to 0. When the number of bits per pixel is smaller than 8, several pixels
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) are packed together in a byte.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) - FB_VISUAL_MONO10
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) Pixels are black or white and stored on a number of bits (typically one)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) specified by the variable screen information bpp field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) Black pixels are represented by all bits set to 0 and white pixels by all bits
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) set to 1. When the number of bits per pixel is smaller than 8, several pixels
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) are packed together in a byte.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) - FB_VISUAL_TRUECOLOR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) Pixels are broken into red, green and blue components, and each component
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) indexes a read-only lookup table for the corresponding value. Lookup tables
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) are device-dependent, and provide linear or non-linear ramps.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) Each component is stored in a macropixel according to the variable screen
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) information red, green, blue and transp fields.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) - FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) Pixel values are encoded as indices into a colormap that stores red, green and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) and read-write for FB_VISUAL_PSEUDOCOLOR.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) Each pixel value is stored in the number of bits reported by the variable
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) screen information bits_per_pixel field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) - FB_VISUAL_DIRECTCOLOR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) Pixels are broken into red, green and blue components, and each component
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) indexes a programmable lookup table for the corresponding value.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) Each component is stored in a macropixel according to the variable screen
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) information red, green, blue and transp fields.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) - FB_VISUAL_FOURCC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) Pixels are encoded and interpreted as described by the format FOURCC
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) identifier stored in the variable screen information grayscale field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) 3. Screen information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) ---------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) Screen information are queried by applications using the FBIOGET_FSCREENINFO
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) fb_fix_screeninfo and fb_var_screeninfo structure respectively.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) struct fb_fix_screeninfo stores device independent unchangeable information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) about the frame buffer device and the current format. Those information can't
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) be directly modified by applications, but can be changed by the driver when an
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) application modifies the format::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) struct fb_fix_screeninfo {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) char id[16]; /* identification string eg "TT Builtin" */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) unsigned long smem_start; /* Start of frame buffer mem */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) /* (physical address) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) __u32 smem_len; /* Length of frame buffer mem */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) __u32 type; /* see FB_TYPE_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) __u32 type_aux; /* Interleave for interleaved Planes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) __u32 visual; /* see FB_VISUAL_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) __u16 xpanstep; /* zero if no hardware panning */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) __u16 ypanstep; /* zero if no hardware panning */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) __u16 ywrapstep; /* zero if no hardware ywrap */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) __u32 line_length; /* length of a line in bytes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) unsigned long mmio_start; /* Start of Memory Mapped I/O */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) /* (physical address) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) __u32 mmio_len; /* Length of Memory Mapped I/O */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) __u32 accel; /* Indicate to driver which */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) /* specific chip/card we have */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) __u16 capabilities; /* see FB_CAP_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) __u16 reserved[2]; /* Reserved for future compatibility */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) struct fb_var_screeninfo stores device independent changeable information
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) about a frame buffer device, its current format and video mode, as well as
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) other miscellaneous parameters::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) struct fb_var_screeninfo {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) __u32 xres; /* visible resolution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) __u32 yres;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) __u32 xres_virtual; /* virtual resolution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) __u32 yres_virtual;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) __u32 xoffset; /* offset from virtual to visible */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) __u32 yoffset; /* resolution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) __u32 bits_per_pixel; /* guess what */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) __u32 grayscale; /* 0 = color, 1 = grayscale, */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) /* >1 = FOURCC */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) struct fb_bitfield red; /* bitfield in fb mem if true color, */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) struct fb_bitfield green; /* else only length is significant */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) struct fb_bitfield blue;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) struct fb_bitfield transp; /* transparency */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) __u32 nonstd; /* != 0 Non standard pixel format */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) __u32 activate; /* see FB_ACTIVATE_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) __u32 height; /* height of picture in mm */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) __u32 width; /* width of picture in mm */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) /* Timing: All values in pixclocks, except pixclock (of course) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) __u32 pixclock; /* pixel clock in ps (pico seconds) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) __u32 left_margin; /* time from sync to picture */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) __u32 right_margin; /* time from picture to sync */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) __u32 upper_margin; /* time from sync to picture */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) __u32 lower_margin;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) __u32 hsync_len; /* length of horizontal sync */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) __u32 vsync_len; /* length of vertical sync */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) __u32 sync; /* see FB_SYNC_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) __u32 vmode; /* see FB_VMODE_* */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) __u32 rotate; /* angle we rotate counter clockwise */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) __u32 colorspace; /* colorspace for FOURCC-based modes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) __u32 reserved[4]; /* Reserved for future compatibility */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) To modify variable information, applications call the FBIOPUT_VSCREENINFO
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) ioctl with a pointer to a fb_var_screeninfo structure. If the call is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) successful, the driver will update the fixed screen information accordingly.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) Instead of filling the complete fb_var_screeninfo structure manually,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) applications should call the FBIOGET_VSCREENINFO ioctl and modify only the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228) fields they care about.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) 4. Format configuration
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) -----------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) Frame buffer devices offer two ways to configure the frame buffer format: the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) legacy API and the FOURCC-based API.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238) The legacy API has been the only frame buffer format configuration API for a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) long time and is thus widely used by application. It is the recommended API
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) for applications when using RGB and grayscale formats, as well as legacy
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241) non-standard formats.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243) To select a format, applications set the fb_var_screeninfo bits_per_pixel field
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244) to the desired frame buffer depth. Values up to 8 will usually map to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) monochrome, grayscale or pseudocolor visuals, although this is not required.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247) - For grayscale formats, applications set the grayscale field to one. The red,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248) blue, green and transp fields must be set to 0 by applications and ignored by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) drivers. Drivers must fill the red, blue and green offsets to 0 and lengths
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250) to the bits_per_pixel value.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252) - For pseudocolor formats, applications set the grayscale field to zero. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253) red, blue, green and transp fields must be set to 0 by applications and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254) ignored by drivers. Drivers must fill the red, blue and green offsets to 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255) and lengths to the bits_per_pixel value.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257) - For truecolor and directcolor formats, applications set the grayscale field
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258) to zero, and the red, blue, green and transp fields to describe the layout of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) color components in memory::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261) struct fb_bitfield {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262) __u32 offset; /* beginning of bitfield */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) __u32 length; /* length of bitfield */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264) __u32 msb_right; /* != 0 : Most significant bit is */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265) /* right */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) Pixel values are bits_per_pixel wide and are split in non-overlapping red,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 269) green, blue and alpha (transparency) components. Location and size of each
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 270) component in the pixel value are described by the fb_bitfield offset and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 271) length fields. Offset are computed from the right.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 272)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 273) Pixels are always stored in an integer number of bytes. If the number of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 274) bits per pixel is not a multiple of 8, pixel values are padded to the next
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 275) multiple of 8 bits.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 276)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 277) Upon successful format configuration, drivers update the fb_fix_screeninfo
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 278) type, visual and line_length fields depending on the selected format.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 279)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 280)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 281) The FOURCC-based API replaces format descriptions by four character codes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 282) (FOURCC). FOURCCs are abstract identifiers that uniquely define a format
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 283) without explicitly describing it. This is the only API that supports YUV
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 284) formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 285) and grayscale formats.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 286)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 287) Drivers that support the FOURCC-based API report this capability by setting
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 288) the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 289)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 290) FOURCC definitions are located in the linux/videodev2.h header. However, and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 291) despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 292) and don't require usage of the V4L2 subsystem. FOURCC documentation is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 293) available in Documentation/userspace-api/media/v4l/pixfmt.rst.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 294)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 295) To select a format, applications set the grayscale field to the desired FOURCC.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 296) For YUV formats, they should also select the appropriate colorspace by setting
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 297) the colorspace field to one of the colorspaces listed in linux/videodev2.h and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 298) documented in Documentation/userspace-api/media/v4l/colorspaces.rst.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 299)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 300) The red, green, blue and transp fields are not used with the FOURCC-based API.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 301) For forward compatibility reasons applications must zero those fields, and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 302) drivers must ignore them. Values other than 0 may get a meaning in future
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 303) extensions.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 304)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 305) Upon successful format configuration, drivers update the fb_fix_screeninfo
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 306) type, visual and line_length fields depending on the selected format. The type
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 307) and visual fields are set to FB_TYPE_FOURCC and FB_VISUAL_FOURCC respectively.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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