€•ý/      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/driver-api/media/v4l2-intro”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/zh_TW/driver-api/media/v4l2-intro”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/it_IT/driver-api/media/v4l2-intro”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/ja_JP/driver-api/media/v4l2-intro”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/ko_KR/driver-api/media/v4l2-intro”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ//translations/sp_SP/driver-api/media/v4l2-intro”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒI/var/lib/git/docbuild/linux/Documentation/driver-api/media/v4l2-intro.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒIntroduction”h]”hŒIntroduction”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h KubhŒ	paragraph”“”)”}”(hŒéThe V4L2 drivers tend to be very complex due to the complexity of the
hardware: most devices have multiple ICs, export multiple device nodes in
/dev, and create also non-V4L2 devices such as DVB, ALSA, FB, I2C and input
(IR) devices.”h]”hŒéThe V4L2 drivers tend to be very complex due to the complexity of the
hardware: most devices have multiple ICs, export multiple device nodes in
/dev, and create also non-V4L2 devices such as DVB, ALSA, FB, I2C and input
(IR) devices.”…””}”(hhËhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hX0  Especially the fact that V4L2 drivers have to setup supporting ICs to
do audio/video muxing/encoding/decoding makes it more complex than most.
Usually these ICs are connected to the main bridge driver through one or
more I2C buses, but other buses can also be used. Such devices are
called 'sub-devices'.”h]”hX4  Especially the fact that V4L2 drivers have to setup supporting ICs to
do audio/video muxing/encoding/decoding makes it more complex than most.
Usually these ICs are connected to the main bridge driver through one or
more I2C buses, but other buses can also be used. Such devices are
called â€˜sub-devicesâ€™.”…””}”(hhÙhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hŒÓFor a long time the framework was limited to the video_device struct for
creating V4L device nodes and video_buf for handling the video buffers
(note that this document does not discuss the video_buf framework).”h]”hŒÓFor a long time the framework was limited to the video_device struct for
creating V4L device nodes and video_buf for handling the video buffers
(note that this document does not discuss the video_buf framework).”…””}”(hhçhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hŒÇThis meant that all drivers had to do the setup of device instances and
connecting to sub-devices themselves. Some of this is quite complicated
to do right and many drivers never did do it correctly.”h]”hŒÇThis meant that all drivers had to do the setup of device instances and
connecting to sub-devices themselves. Some of this is quite complicated
to do right and many drivers never did do it correctly.”…””}”(hhõhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hŒaThere is also a lot of common code that could never be refactored due to
the lack of a framework.”h]”hŒaThere is also a lot of common code that could never be refactored due to
the lack of a framework.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hŒÂSo this framework sets up the basic building blocks that all drivers
need and this same framework should make it much easier to refactor
common code into utility functions shared by all drivers.”h]”hŒÂSo this framework sets up the basic building blocks that all drivers
need and this same framework should make it much easier to refactor
common code into utility functions shared by all drivers.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hX  A good example to look at as a reference is the v4l2-pci-skeleton.c
source that is available in samples/v4l/. It is a skeleton driver for
a PCI capture card, and demonstrates how to use the V4L2 driver
framework. It can be used as a template for real PCI video capture driver.”h]”hX  A good example to look at as a reference is the v4l2-pci-skeleton.c
source that is available in samples/v4l/. It is a skeleton driver for
a PCI capture card, and demonstrates how to use the V4L2 driver
framework. It can be used as a template for real PCI video capture driver.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K hh¶hžhubeh}”(h]”Œintroduction”ah ]”h"]”Œintroduction”ah$]”h&]”uh1h´hhhžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒStructure of a V4L driver”h]”hŒStructure of a V4L driver”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj5  hžhhŸh³h K&ubhÊ)”}”(hŒ)All drivers have the following structure:”h]”hŒ)All drivers have the following structure:”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K(hj5  hžhubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒ?A struct for each device instance containing the device state.
”h]”hÊ)”}”(hŒ>A struct for each device instance containing the device state.”h]”hŒ>A struct for each device instance containing the device state.”…””}”(hj_  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K*hj[  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jY  hjV  hžhhŸh³h NubjZ  )”}”(hŒ;A way of initializing and commanding sub-devices (if any).
”h]”hÊ)”}”(hŒ:A way of initializing and commanding sub-devices (if any).”h]”hŒ:A way of initializing and commanding sub-devices (if any).”…””}”(hjw  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K,hjs  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jY  hjV  hžhhŸh³h NubjZ  )”}”(hŒtCreating V4L2 device nodes (/dev/videoX, /dev/vbiX and /dev/radioX)
and keeping track of device-node specific data.
”h]”hÊ)”}”(hŒsCreating V4L2 device nodes (/dev/videoX, /dev/vbiX and /dev/radioX)
and keeping track of device-node specific data.”h]”hŒsCreating V4L2 device nodes (/dev/videoX, /dev/vbiX and /dev/radioX)
and keeping track of device-node specific data.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K.hj‹  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jY  hjV  hžhhŸh³h NubjZ  )”}”(hŒ<Filehandle-specific structs containing per-filehandle data;
”h]”hÊ)”}”(hŒ;Filehandle-specific structs containing per-filehandle data;”h]”hŒ;Filehandle-specific structs containing per-filehandle data;”…””}”(hj§  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K1hj£  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jY  hjV  hžhhŸh³h NubjZ  )”}”(hŒvideo buffer handling.
”h]”hÊ)”}”(hŒvideo buffer handling.”h]”hŒvideo buffer handling.”…””}”(hj¿  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K3hj»  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jY  hjV  hžhhŸh³h Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ)”uh1jT  hj5  hžhhŸh³h K*ubhÊ)”}”(hŒ0This is a rough schematic of how it all relates:”h]”hŒ0This is a rough schematic of how it all relates:”…””}”(hjÞ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K5hj5  hžhubhŒliteral_block”“”)”}”(hŒldevice instances
  |
  +-sub-device instances
  |
  \-V4L2 device nodes
      |
      \-filehandle instances”h]”hŒldevice instances
  |
  +-sub-device instances
  |
  \-V4L2 device nodes
      |
      \-filehandle instances”…””}”hjî  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²Œforce”‰Œlanguage”Œnone”Œhighlight_args”}”uh1jì  hŸh³h K7hj5  hžhubeh}”(h]”Œstructure-of-a-v4l-driver”ah ]”h"]”Œstructure of a v4l driver”ah$]”h&]”uh1h´hhhžhhŸh³h K&ubhµ)”}”(hhh]”(hº)”}”(hŒStructure of the V4L2 framework”h]”hŒStructure of the V4L2 framework”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj	  hžhhŸh³h KCubhÊ)”}”(hX  The framework closely resembles the driver structure: it has a v4l2_device
struct for the device instance data, a v4l2_subdev struct to refer to
sub-device instances, the video_device struct stores V4L2 device node data
and the v4l2_fh struct keeps track of filehandle instances.”h]”hX  The framework closely resembles the driver structure: it has a v4l2_device
struct for the device instance data, a v4l2_subdev struct to refer to
sub-device instances, the video_device struct stores V4L2 device node data
and the v4l2_fh struct keeps track of filehandle instances.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KEhj	  hžhubhÊ)”}”(hŒÕThe V4L2 framework also optionally integrates with the media framework. If a
driver sets the struct v4l2_device mdev field, sub-devices and video nodes
will automatically appear in the media framework as entities.”h]”hŒÕThe V4L2 framework also optionally integrates with the media framework. If a
driver sets the struct v4l2_device mdev field, sub-devices and video nodes
will automatically appear in the media framework as entities.”…””}”(hj(  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KJhj	  hžhubeh}”(h]”Œstructure-of-the-v4l2-framework”ah ]”h"]”Œstructure of the v4l2 framework”ah$]”h&]”uh1h´hhhžhhŸh³h KCubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”ja  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j2  j/  j  j  j;  j8  uŒ	nametypes”}”(j2  ‰j  ‰j;  ‰uh}”(j/  h¶j  j5  j8  j	  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.