€•å       Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ/translations/zh_CN/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/zh_TW/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/it_IT/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/ja_JP/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/ko_KR/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/sp_SP/fb/api”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒThe Frame Buffer Device API”h]”hŒThe Frame Buffer Device API”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒ4/var/lib/git/docbuild/linux/Documentation/fb/api.rst”h KubhŒ	paragraph”“”)”}”(hŒLast revised: June 21, 2011”h]”hŒLast revised: June 21, 2011”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒ0. Introduction”h]”hŒ0. Introduction”…””}”(hhÊhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhÇhžhhŸh¶h K	ubh¸)”}”(hŒ»This document describes the frame buffer API used by applications to interact
with frame buffer devices. In-kernel APIs between device drivers and the frame
buffer core are not described.”h]”hŒ»This document describes the frame buffer API used by applications to interact
with frame buffer devices. In-kernel APIs between device drivers and the frame
buffer core are not described.”…””}”(hhØhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hX  Due to a lack of documentation in the original frame buffer API, drivers
behaviours differ in subtle (and not so subtle) ways. This document describes
the recommended API implementation, but applications should be prepared to
deal with different behaviours.”h]”hX  Due to a lack of documentation in the original frame buffer API, drivers
behaviours differ in subtle (and not so subtle) ways. This document describes
the recommended API implementation, but applications should be prepared to
deal with different behaviours.”…””}”(hhæhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubeh}”(h]”Œintroduction”ah ]”h"]”Œ0. introduction”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K	ubh¢)”}”(hhh]”(h§)”}”(hŒ1. Capabilities”h]”hŒ1. Capabilities”…””}”(hhÿhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhühžhhŸh¶h Kubh¸)”}”(hŒ`Device and driver capabilities are reported in the fixed screen information
capabilities field::”h]”hŒ_Device and driver capabilities are reported in the fixed screen information
capabilities field:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhühžhubhŒliteral_block”“”)”}”(hŒzstruct fb_fix_screeninfo {
      ...
      __u16 capabilities;             /* see FB_CAP_*                 */
      ...
};”h]”hŒzstruct fb_fix_screeninfo {
      ...
      __u16 capabilities;             /* see FB_CAP_*                 */
      ...
};”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j  hŸh¶h Khhühžhubh¸)”}”(hŒoApplication should use those capabilities to find out what features they can
expect from the device and driver.”h]”hŒoApplication should use those capabilities to find out what features they can
expect from the device and driver.”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K!hhühžhubhŒbullet_list”“”)”}”(hhh]”hŒ	list_item”“”)”}”(hŒFB_CAP_FOURCC
”h]”h¸)”}”(hŒFB_CAP_FOURCC”h]”hŒFB_CAP_FOURCC”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K$hjB  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj=  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1j;  hŸh¶h K$hhühžhubh¸)”}”(hŒ¼The driver supports the four character code (FOURCC) based format setting API.
When supported, formats are configured using a FOURCC instead of manually
specifying color components layout.”h]”hŒ¼The driver supports the four character code (FOURCC) based format setting API.
When supported, formats are configured using a FOURCC instead of manually
specifying color components layout.”…””}”(hjb  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K&hhühžhubeh}”(h]”Œcapabilities”ah ]”h"]”Œ1. capabilities”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒ2. Types and visuals”h]”hŒ2. Types and visuals”…””}”(hj{  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjx  hžhhŸh¶h K,ubh¸)”}”(hŒÔPixels are stored in memory in hardware-dependent formats. Applications need
to be aware of the pixel storage format in order to write image data to the
frame buffer memory in the format expected by the hardware.”h]”hŒÔPixels are stored in memory in hardware-dependent formats. Applications need
to be aware of the pixel storage format in order to write image data to the
frame buffer memory in the format expected by the hardware.”…””}”(hj‰  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K.hjx  hžhubh¸)”}”(hŒØFormats are described by frame buffer types and visuals. Some visuals require
additional information, which are stored in the variable screen information
bits_per_pixel, grayscale, red, green, blue and transp fields.”h]”hŒØFormats are described by frame buffer types and visuals. Some visuals require
additional information, which are stored in the variable screen information
bits_per_pixel, grayscale, red, green, blue and transp fields.”…””}”(hj—  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K2hjx  hžhubh¸)”}”(hŒºVisuals describe how color information is encoded and assembled to create
macropixels. Types describe how macropixels are stored in memory. The following
types and visuals are supported.”h]”hŒºVisuals describe how color information is encoded and assembled to create
macropixels. Types describe how macropixels are stored in memory. The following
types and visuals are supported.”…””}”(hj¥  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K6hjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_TYPE_PACKED_PIXELS
”h]”h¸)”}”(hŒFB_TYPE_PACKED_PIXELS”h]”hŒFB_TYPE_PACKED_PIXELS”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K:hj¶  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj³  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h K:hjx  hžhubh¸)”}”(hŒæMacropixels are stored contiguously in a single plane. If the number of bits
per macropixel is not a multiple of 8, whether macropixels are padded to the
next multiple of 8 bits or packed together into bytes depends on the visual.”h]”hŒæMacropixels are stored contiguously in a single plane. If the number of bits
per macropixel is not a multiple of 8, whether macropixels are padded to the
next multiple of 8 bits or packed together into bytes depends on the visual.”…””}”(hjÔ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K<hjx  hžhubh¸)”}”(hŒsPadding at end of lines may be present and is then reported through the fixed
screen information line_length field.”h]”hŒsPadding at end of lines may be present and is then reported through the fixed
screen information line_length field.”…””}”(hjâ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K@hjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_TYPE_PLANES
”h]”h¸)”}”(hŒFB_TYPE_PLANES”h]”hŒFB_TYPE_PLANES”…””}”(hj÷  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KChjó  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjð  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h KChjx  hžhubh¸)”}”(hŒ¨Macropixels are split across multiple planes. The number of planes is equal to
the number of bits per macropixel, with plane i'th storing i'th bit from all
macropixels.”h]”hŒ¬Macropixels are split across multiple planes. The number of planes is equal to
the number of bits per macropixel, with plane iâ€™th storing iâ€™th bit from all
macropixels.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KEhjx  hžhubh¸)”}”(hŒ*Planes are located contiguously in memory.”h]”hŒ*Planes are located contiguously in memory.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KIhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_TYPE_INTERLEAVED_PLANES
”h]”h¸)”}”(hŒFB_TYPE_INTERLEAVED_PLANES”h]”hŒFB_TYPE_INTERLEAVED_PLANES”…””}”(hj4  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KKhj0  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj-  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h KKhjx  hžhubh¸)”}”(hŒ¨Macropixels are split across multiple planes. The number of planes is equal to
the number of bits per macropixel, with plane i'th storing i'th bit from all
macropixels.”h]”hŒ¬Macropixels are split across multiple planes. The number of planes is equal to
the number of bits per macropixel, with plane iâ€™th storing iâ€™th bit from all
macropixels.”…””}”(hjN  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KMhjx  hžhubh¸)”}”(hŒîPlanes are interleaved in memory. The interleave factor, defined as the
distance in bytes between the beginning of two consecutive interleaved blocks
belonging to different planes, is stored in the fixed screen information
type_aux field.”h]”hŒîPlanes are interleaved in memory. The interleave factor, defined as the
distance in bytes between the beginning of two consecutive interleaved blocks
belonging to different planes, is stored in the fixed screen information
type_aux field.”…””}”(hj\  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KQhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_TYPE_FOURCC
”h]”h¸)”}”(hŒFB_TYPE_FOURCC”h]”hŒFB_TYPE_FOURCC”…””}”(hjq  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KVhjm  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjj  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h KVhjx  hžhubh¸)”}”(hŒˆMacropixels are stored in memory as described by the format FOURCC identifier
stored in the variable screen information grayscale field.”h]”hŒˆMacropixels are stored in memory as described by the format FOURCC identifier
stored in the variable screen information grayscale field.”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KXhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_VISUAL_MONO01
”h]”h¸)”}”(hŒFB_VISUAL_MONO01”h]”hŒFB_VISUAL_MONO01”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K[hjœ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj™  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h K[hjx  hžhubh¸)”}”(hŒ€Pixels are black or white and stored on a number of bits (typically one)
specified by the variable screen information bpp field.”h]”hŒ€Pixels are black or white and stored on a number of bits (typically one)
specified by the variable screen information bpp field.”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K]hjx  hžhubh¸)”}”(hŒ»Black pixels are represented by all bits set to 1 and white pixels by all bits
set to 0. When the number of bits per pixel is smaller than 8, several pixels
are packed together in a byte.”h]”hŒ»Black pixels are represented by all bits set to 1 and white pixels by all bits
set to 0. When the number of bits per pixel is smaller than 8, several pixels
are packed together in a byte.”…””}”(hjÈ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K`hjx  hžhubh¸)”}”(hŒCFB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.”h]”hŒCFB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.”…””}”(hjÖ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kdhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_VISUAL_MONO10
”h]”h¸)”}”(hŒFB_VISUAL_MONO10”h]”hŒFB_VISUAL_MONO10”…””}”(hjë  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kfhjç  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjä  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h Kfhjx  hžhubh¸)”}”(hŒ€Pixels are black or white and stored on a number of bits (typically one)
specified by the variable screen information bpp field.”h]”hŒ€Pixels are black or white and stored on a number of bits (typically one)
specified by the variable screen information bpp field.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khhjx  hžhubh¸)”}”(hŒ»Black pixels are represented by all bits set to 0 and white pixels by all bits
set to 1. When the number of bits per pixel is smaller than 8, several pixels
are packed together in a byte.”h]”hŒ»Black pixels are represented by all bits set to 0 and white pixels by all bits
set to 1. When the number of bits per pixel is smaller than 8, several pixels
are packed together in a byte.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kkhjx  hžhubh¸)”}”(hŒCFB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.”h]”hŒCFB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kohjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_VISUAL_TRUECOLOR
”h]”h¸)”}”(hŒFB_VISUAL_TRUECOLOR”h]”hŒFB_VISUAL_TRUECOLOR”…””}”(hj6  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kqhj2  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj/  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h Kqhjx  hžhubh¸)”}”(hŒÓPixels are broken into red, green and blue components, and each component
indexes a read-only lookup table for the corresponding value. Lookup tables
are device-dependent, and provide linear or non-linear ramps.”h]”hŒÓPixels are broken into red, green and blue components, and each component
indexes a read-only lookup table for the corresponding value. Lookup tables
are device-dependent, and provide linear or non-linear ramps.”…””}”(hjP  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kshjx  hžhubh¸)”}”(hŒyEach component is stored in a macropixel according to the variable screen
information red, green, blue and transp fields.”h]”hŒyEach component is stored in a macropixel according to the variable screen
information red, green, blue and transp fields.”…””}”(hj^  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kwhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒ7FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR
”h]”h¸)”}”(hŒ6FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR”h]”hŒ6FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR”…””}”(hjs  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kzhjo  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjl  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h Kzhjx  hžhubh¸)”}”(hŒÄPixel values are encoded as indices into a colormap that stores red, green and
blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
and read-write for FB_VISUAL_PSEUDOCOLOR.”h]”hŒÄPixel values are encoded as indices into a colormap that stores red, green and
blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
and read-write for FB_VISUAL_PSEUDOCOLOR.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K|hjx  hžhubh¸)”}”(hŒrEach pixel value is stored in the number of bits reported by the variable
screen information bits_per_pixel field.”h]”hŒrEach pixel value is stored in the number of bits reported by the variable
screen information bits_per_pixel field.”…””}”(hj›  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K€hjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_VISUAL_DIRECTCOLOR
”h]”h¸)”}”(hŒFB_VISUAL_DIRECTCOLOR”h]”hŒFB_VISUAL_DIRECTCOLOR”…””}”(hj°  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kƒhj¬  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hj©  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h Kƒhjx  hžhubh¸)”}”(hŒŠPixels are broken into red, green and blue components, and each component
indexes a programmable lookup table for the corresponding value.”h]”hŒŠPixels are broken into red, green and blue components, and each component
indexes a programmable lookup table for the corresponding value.”…””}”(hjÊ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K…hjx  hžhubh¸)”}”(hŒyEach component is stored in a macropixel according to the variable screen
information red, green, blue and transp fields.”h]”hŒyEach component is stored in a macropixel according to the variable screen
information red, green, blue and transp fields.”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kˆhjx  hžhubj<  )”}”(hhh]”jA  )”}”(hŒFB_VISUAL_FOURCC
”h]”h¸)”}”(hŒFB_VISUAL_FOURCC”h]”hŒFB_VISUAL_FOURCC”…””}”(hjí  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‹hjé  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjæ  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h K‹hjx  hžhubh¸)”}”(hŒ‹Pixels are encoded and  interpreted as described by the format FOURCC
identifier stored in the variable screen information grayscale field.”h]”hŒ‹Pixels are encoded and  interpreted as described by the format FOURCC
identifier stored in the variable screen information grayscale field.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khjx  hžhubeh}”(h]”Œtypes-and-visuals”ah ]”h"]”Œ2. types and visuals”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K,ubh¢)”}”(hhh]”(h§)”}”(hŒ3. Screen information”h]”hŒ3. Screen information”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h K’ubh¸)”}”(hŒÍScreen information are queried by applications using the FBIOGET_FSCREENINFO
and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a
fb_fix_screeninfo and fb_var_screeninfo structure respectively.”h]”hŒÍScreen information are queried by applications using the FBIOGET_FSCREENINFO
and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a
fb_fix_screeninfo and fb_var_screeninfo structure respectively.”…””}”(hj.  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K”hj  hžhubh¸)”}”(hX
  struct fb_fix_screeninfo stores device independent unchangeable information
about the frame buffer device and the current format. Those information can't
be directly modified by applications, but can be changed by the driver when an
application modifies the format::”h]”hX  struct fb_fix_screeninfo stores device independent unchangeable information
about the frame buffer device and the current format. Those information canâ€™t
be directly modified by applications, but can be changed by the driver when an
application modifies the format:”…””}”(hj<  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K˜hj  hžhubj  )”}”(hX9  struct fb_fix_screeninfo {
      char id[16];                    /* identification string eg "TT Builtin" */
      unsigned long smem_start;       /* Start of frame buffer mem */
                                      /* (physical address) */
      __u32 smem_len;                 /* Length of frame buffer mem */
      __u32 type;                     /* see FB_TYPE_*                */
      __u32 type_aux;                 /* Interleave for interleaved Planes */
      __u32 visual;                   /* see FB_VISUAL_*              */
      __u16 xpanstep;                 /* zero if no hardware panning  */
      __u16 ypanstep;                 /* zero if no hardware panning  */
      __u16 ywrapstep;                /* zero if no hardware ywrap    */
      __u32 line_length;              /* length of a line in bytes    */
      unsigned long mmio_start;       /* Start of Memory Mapped I/O   */
                                      /* (physical address) */
      __u32 mmio_len;                 /* Length of Memory Mapped I/O  */
      __u32 accel;                    /* Indicate to driver which     */
                                      /*  specific chip/card we have  */
      __u16 capabilities;             /* see FB_CAP_*                 */
      __u16 reserved[2];              /* Reserved for future compatibility */
};”h]”hX9  struct fb_fix_screeninfo {
      char id[16];                    /* identification string eg "TT Builtin" */
      unsigned long smem_start;       /* Start of frame buffer mem */
                                      /* (physical address) */
      __u32 smem_len;                 /* Length of frame buffer mem */
      __u32 type;                     /* see FB_TYPE_*                */
      __u32 type_aux;                 /* Interleave for interleaved Planes */
      __u32 visual;                   /* see FB_VISUAL_*              */
      __u16 xpanstep;                 /* zero if no hardware panning  */
      __u16 ypanstep;                 /* zero if no hardware panning  */
      __u16 ywrapstep;                /* zero if no hardware ywrap    */
      __u32 line_length;              /* length of a line in bytes    */
      unsigned long mmio_start;       /* Start of Memory Mapped I/O   */
                                      /* (physical address) */
      __u32 mmio_len;                 /* Length of Memory Mapped I/O  */
      __u32 accel;                    /* Indicate to driver which     */
                                      /*  specific chip/card we have  */
      __u16 capabilities;             /* see FB_CAP_*                 */
      __u16 reserved[2];              /* Reserved for future compatibility */
};”…””}”hjJ  sbah}”(h]”h ]”h"]”h$]”h&]”j+  j,  uh1j  hŸh¶h Khj  hžhubh¸)”}”(hŒµstruct fb_var_screeninfo stores device independent changeable information
about a frame buffer device, its current format and video mode, as well as
other miscellaneous parameters::”h]”hŒ´struct fb_var_screeninfo stores device independent changeable information
about a frame buffer device, its current format and video mode, as well as
other miscellaneous parameters:”…””}”(hjX  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K²hj  hžhubj  )”}”(hXV  struct fb_var_screeninfo {
      __u32 xres;                     /* visible resolution           */
      __u32 yres;
      __u32 xres_virtual;             /* virtual resolution           */
      __u32 yres_virtual;
      __u32 xoffset;                  /* offset from virtual to visible */
      __u32 yoffset;                  /* resolution                   */

      __u32 bits_per_pixel;           /* guess what                   */
      __u32 grayscale;                /* 0 = color, 1 = grayscale,    */
                                      /* >1 = FOURCC                  */
      struct fb_bitfield red;         /* bitfield in fb mem if true color, */
      struct fb_bitfield green;       /* else only length is significant */
      struct fb_bitfield blue;
      struct fb_bitfield transp;      /* transparency                 */

      __u32 nonstd;                   /* != 0 Non standard pixel format */

      __u32 activate;                 /* see FB_ACTIVATE_*            */

      __u32 height;                   /* height of picture in mm    */
      __u32 width;                    /* width of picture in mm     */

      __u32 accel_flags;              /* (OBSOLETE) see fb_info.flags */

      /* Timing: All values in pixclocks, except pixclock (of course) */
      __u32 pixclock;                 /* pixel clock in ps (pico seconds) */
      __u32 left_margin;              /* time from sync to picture    */
      __u32 right_margin;             /* time from picture to sync    */
      __u32 upper_margin;             /* time from sync to picture    */
      __u32 lower_margin;
      __u32 hsync_len;                /* length of horizontal sync    */
      __u32 vsync_len;                /* length of vertical sync      */
      __u32 sync;                     /* see FB_SYNC_*                */
      __u32 vmode;                    /* see FB_VMODE_*               */
      __u32 rotate;                   /* angle we rotate counter clockwise */
      __u32 colorspace;               /* colorspace for FOURCC-based modes */
      __u32 reserved[4];              /* Reserved for future compatibility */
};”h]”hXV  struct fb_var_screeninfo {
      __u32 xres;                     /* visible resolution           */
      __u32 yres;
      __u32 xres_virtual;             /* virtual resolution           */
      __u32 yres_virtual;
      __u32 xoffset;                  /* offset from virtual to visible */
      __u32 yoffset;                  /* resolution                   */

      __u32 bits_per_pixel;           /* guess what                   */
      __u32 grayscale;                /* 0 = color, 1 = grayscale,    */
                                      /* >1 = FOURCC                  */
      struct fb_bitfield red;         /* bitfield in fb mem if true color, */
      struct fb_bitfield green;       /* else only length is significant */
      struct fb_bitfield blue;
      struct fb_bitfield transp;      /* transparency                 */

      __u32 nonstd;                   /* != 0 Non standard pixel format */

      __u32 activate;                 /* see FB_ACTIVATE_*            */

      __u32 height;                   /* height of picture in mm    */
      __u32 width;                    /* width of picture in mm     */

      __u32 accel_flags;              /* (OBSOLETE) see fb_info.flags */

      /* Timing: All values in pixclocks, except pixclock (of course) */
      __u32 pixclock;                 /* pixel clock in ps (pico seconds) */
      __u32 left_margin;              /* time from sync to picture    */
      __u32 right_margin;             /* time from picture to sync    */
      __u32 upper_margin;             /* time from sync to picture    */
      __u32 lower_margin;
      __u32 hsync_len;                /* length of horizontal sync    */
      __u32 vsync_len;                /* length of vertical sync      */
      __u32 sync;                     /* see FB_SYNC_*                */
      __u32 vmode;                    /* see FB_VMODE_*               */
      __u32 rotate;                   /* angle we rotate counter clockwise */
      __u32 colorspace;               /* colorspace for FOURCC-based modes */
      __u32 reserved[4];              /* Reserved for future compatibility */
};”…””}”hjf  sbah}”(h]”h ]”h"]”h$]”h&]”j+  j,  uh1j  hŸh¶h K¶hj  hžhubh¸)”}”(hŒÜTo modify variable information, applications call the FBIOPUT_VSCREENINFO
ioctl with a pointer to a fb_var_screeninfo structure. If the call is
successful, the driver will update the fixed screen information accordingly.”h]”hŒÜTo modify variable information, applications call the FBIOPUT_VSCREENINFO
ioctl with a pointer to a fb_var_screeninfo structure. If the call is
successful, the driver will update the fixed screen information accordingly.”…””}”(hjt  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÞhj  hžhubh¸)”}”(hŒ¨Instead of filling the complete fb_var_screeninfo structure manually,
applications should call the FBIOGET_VSCREENINFO ioctl and modify only the
fields they care about.”h]”hŒ¨Instead of filling the complete fb_var_screeninfo structure manually,
applications should call the FBIOGET_VSCREENINFO ioctl and modify only the
fields they care about.”…””}”(hj‚  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kâhj  hžhubeh}”(h]”Œscreen-information”ah ]”h"]”Œ3. screen information”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K’ubh¢)”}”(hhh]”(h§)”}”(hŒ4. Format configuration”h]”hŒ4. Format configuration”…””}”(hj›  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj˜  hžhhŸh¶h Kèubh¸)”}”(hŒrFrame buffer devices offer two ways to configure the frame buffer format: the
legacy API and the FOURCC-based API.”h]”hŒrFrame buffer devices offer two ways to configure the frame buffer format: the
legacy API and the FOURCC-based API.”…””}”(hj©  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kêhj˜  hžhubh¸)”}”(hŒ÷The legacy API has been the only frame buffer format configuration API for a
long time and is thus widely used by application. It is the recommended API
for applications when using RGB and grayscale formats, as well as legacy
non-standard formats.”h]”hŒ÷The legacy API has been the only frame buffer format configuration API for a
long time and is thus widely used by application. It is the recommended API
for applications when using RGB and grayscale formats, as well as legacy
non-standard formats.”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kîhj˜  hžhubh¸)”}”(hŒâTo select a format, applications set the fb_var_screeninfo bits_per_pixel field
to the desired frame buffer depth. Values up to 8 will usually map to
monochrome, grayscale or pseudocolor visuals, although this is not required.”h]”hŒâTo select a format, applications set the fb_var_screeninfo bits_per_pixel field
to the desired frame buffer depth. Values up to 8 will usually map to
monochrome, grayscale or pseudocolor visuals, although this is not required.”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kóhj˜  hžhubj<  )”}”(hhh]”(jA  )”}”(hX  For grayscale formats, applications set the grayscale field to one. The red,
blue, green and transp fields must be set to 0 by applications and ignored by
drivers. Drivers must fill the red, blue and green offsets to 0 and lengths
to the bits_per_pixel value.
”h]”h¸)”}”(hX  For grayscale formats, applications set the grayscale field to one. The red,
blue, green and transp fields must be set to 0 by applications and ignored by
drivers. Drivers must fill the red, blue and green offsets to 0 and lengths
to the bits_per_pixel value.”h]”hX  For grayscale formats, applications set the grayscale field to one. The red,
blue, green and transp fields must be set to 0 by applications and ignored by
drivers. Drivers must fill the red, blue and green offsets to 0 and lengths
to the bits_per_pixel value.”…””}”(hjÚ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K÷hjÖ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjÓ  hžhhŸh¶h NubjA  )”}”(hX  For pseudocolor formats, applications set the grayscale field to zero. The
red, blue, green and transp fields must be set to 0 by applications and
ignored by drivers. Drivers must fill the red, blue and green offsets to 0
and lengths to the bits_per_pixel value.
”h]”h¸)”}”(hX  For pseudocolor formats, applications set the grayscale field to zero. The
red, blue, green and transp fields must be set to 0 by applications and
ignored by drivers. Drivers must fill the red, blue and green offsets to 0
and lengths to the bits_per_pixel value.”h]”hX  For pseudocolor formats, applications set the grayscale field to zero. The
red, blue, green and transp fields must be set to 0 by applications and
ignored by drivers. Drivers must fill the red, blue and green offsets to 0
and lengths to the bits_per_pixel value.”…””}”(hjò  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kühjî  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjÓ  hžhhŸh¶h NubjA  )”}”(hXŸ  For truecolor and directcolor formats, applications set the grayscale field
to zero, and the red, blue, green and transp fields to describe the layout of
color components in memory::

  struct fb_bitfield {
      __u32 offset;                   /* beginning of bitfield        */
      __u32 length;                   /* length of bitfield           */
      __u32 msb_right;                /* != 0 : Most significant bit is */
                                      /* right */
  };

Pixel values are bits_per_pixel wide and are split in non-overlapping red,
green, blue and alpha (transparency) components. Location and size of each
component in the pixel value are described by the fb_bitfield offset and
length fields. Offset are computed from the right.

Pixels are always stored in an integer number of bytes. If the number of
bits per pixel is not a multiple of 8, pixel values are padded to the next
multiple of 8 bits.
”h]”(h¸)”}”(hŒ¶For truecolor and directcolor formats, applications set the grayscale field
to zero, and the red, blue, green and transp fields to describe the layout of
color components in memory::”h]”hŒµFor truecolor and directcolor formats, applications set the grayscale field
to zero, and the red, blue, green and transp fields to describe the layout of
color components in memory:”…””}”(hj
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj  ubj  )”}”(hX  struct fb_bitfield {
    __u32 offset;                   /* beginning of bitfield        */
    __u32 length;                   /* length of bitfield           */
    __u32 msb_right;                /* != 0 : Most significant bit is */
                                    /* right */
};”h]”hX  struct fb_bitfield {
    __u32 offset;                   /* beginning of bitfield        */
    __u32 length;                   /* length of bitfield           */
    __u32 msb_right;                /* != 0 : Most significant bit is */
                                    /* right */
};”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”j+  j,  uh1j  hŸh¶h Mhj  ubh¸)”}”(hX  Pixel values are bits_per_pixel wide and are split in non-overlapping red,
green, blue and alpha (transparency) components. Location and size of each
component in the pixel value are described by the fb_bitfield offset and
length fields. Offset are computed from the right.”h]”hX  Pixel values are bits_per_pixel wide and are split in non-overlapping red,
green, blue and alpha (transparency) components. Location and size of each
component in the pixel value are described by the fb_bitfield offset and
length fields. Offset are computed from the right.”…””}”(hj&  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj  ubh¸)”}”(hŒ§Pixels are always stored in an integer number of bytes. If the number of
bits per pixel is not a multiple of 8, pixel values are padded to the next
multiple of 8 bits.”h]”hŒ§Pixels are always stored in an integer number of bytes. If the number of
bits per pixel is not a multiple of 8, pixel values are padded to the next
multiple of 8 bits.”…””}”(hj4  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j@  hjÓ  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j`  ja  uh1j;  hŸh¶h K÷hj˜  hžhubh¸)”}”(hŒUpon successful format configuration, drivers update the fb_fix_screeninfo
type, visual and line_length fields depending on the selected format.”h]”hŒUpon successful format configuration, drivers update the fb_fix_screeninfo
type, visual and line_length fields depending on the selected format.”…””}”(hjN  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj˜  hžhubh¸)”}”(hXA  The FOURCC-based API replaces format descriptions by four character codes
(FOURCC). FOURCCs are abstract identifiers that uniquely define a format
without explicitly describing it. This is the only API that supports YUV
formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
and grayscale formats.”h]”hXA  The FOURCC-based API replaces format descriptions by four character codes
(FOURCC). FOURCCs are abstract identifiers that uniquely define a format
without explicitly describing it. This is the only API that supports YUV
formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
and grayscale formats.”…””}”(hj\  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj˜  hžhubh¸)”}”(hŒŽDrivers that support the FOURCC-based API report this capability by setting
the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field.”h]”hŒŽDrivers that support the FOURCC-based API report this capability by setting
the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field.”…””}”(hjj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj˜  hžhubh¸)”}”(hX!  FOURCC definitions are located in the linux/videodev2.h header. However, and
despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2
and don't require usage of the V4L2 subsystem. FOURCC documentation is
available in Documentation/userspace-api/media/v4l/pixfmt.rst.”h]”hX#  FOURCC definitions are located in the linux/videodev2.h header. However, and
despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2
and donâ€™t require usage of the V4L2 subsystem. FOURCC documentation is
available in Documentation/userspace-api/media/v4l/pixfmt.rst.”…””}”(hjx  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M"hj˜  hžhubh¸)”}”(hX2  To select a format, applications set the grayscale field to the desired FOURCC.
For YUV formats, they should also select the appropriate colorspace by setting
the colorspace field to one of the colorspaces listed in linux/videodev2.h and
documented in Documentation/userspace-api/media/v4l/colorspaces.rst.”h]”hX2  To select a format, applications set the grayscale field to the desired FOURCC.
For YUV formats, they should also select the appropriate colorspace by setting
the colorspace field to one of the colorspaces listed in linux/videodev2.h and
documented in Documentation/userspace-api/media/v4l/colorspaces.rst.”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M'hj˜  hžhubh¸)”}”(hŒïThe red, green, blue and transp fields are not used with the FOURCC-based API.
For forward compatibility reasons applications must zero those fields, and
drivers must ignore them. Values other than 0 may get a meaning in future
extensions.”h]”hŒïThe red, green, blue and transp fields are not used with the FOURCC-based API.
For forward compatibility reasons applications must zero those fields, and
drivers must ignore them. Values other than 0 may get a meaning in future
extensions.”…””}”(hj”  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M,hj˜  hžhubh¸)”}”(hŒèUpon successful format configuration, drivers update the fb_fix_screeninfo
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