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linux/Documentation/ABI/testing/configfs-usb-gadget-uvc
Joel Pepper b206548be6 usb: gadget: uvc: configfs: Add bFrameIndex attributes 
- Add bFrameIndex as a UVCG_FRAME_ATTR_RO for each frame size.
- Automatically assign ascending bFrameIndex to each frame in a format.

Before all "bFrameindex" attributes were set to "1" with no way to
configure the gadget otherwise. This resulted in the host always
negotiating for bFrameIndex 1 (i.e. the first frame size of the gadget).
After the negotiation the host driver will set the user or application
selected frame size, while the gadget is actually set to the first frame
size.

Now, when the containing format is linked into the streaming header,
iterate over all child frame descriptors and assign ascending indices.
The automatically assigned indices can be read from the new read only
bFrameIndex configfs attribute in each frame descriptor item.

Signed-off-by: Joel Pepper <joel.pepper@rwth-aachen.de>
[Simplified documentation, renamed function, blank space update]
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
2018-09-24 19:00:35 +03:00

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What: /config/usb-gadget/gadget/functions/uvc.name
Date: Dec 2014
KernelVersion: 4.0
Description: UVC function directory
streaming_maxburst - 0..15 (ss only)
streaming_maxpacket - 1..1023 (fs), 1..3072 (hs/ss)
streaming_interval - 1..16
What: /config/usb-gadget/gadget/functions/uvc.name/control
Date: Dec 2014
KernelVersion: 4.0
Description: Control descriptors
All attributes read only:
bInterfaceNumber - USB interface number for this
streaming interface
What: /config/usb-gadget/gadget/functions/uvc.name/control/class
Date: Dec 2014
KernelVersion: 4.0
Description: Class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/class/ss
Date: Dec 2014
KernelVersion: 4.0
Description: Super speed control class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/class/fs
Date: Dec 2014
KernelVersion: 4.0
Description: Full speed control class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/terminal
Date: Dec 2014
KernelVersion: 4.0
Description: Terminal descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/terminal/output
Date: Dec 2014
KernelVersion: 4.0
Description: Output terminal descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/terminal/output/default
Date: Dec 2014
KernelVersion: 4.0
Description: Default output terminal descriptors
All attributes read only:
iTerminal - index of string descriptor
bSourceID - id of the terminal to which this terminal
is connected
bAssocTerminal - id of the input terminal to which this output
terminal is associated
wTerminalType - terminal type
bTerminalID - a non-zero id of this terminal
What: /config/usb-gadget/gadget/functions/uvc.name/control/terminal/camera
Date: Dec 2014
KernelVersion: 4.0
Description: Camera terminal descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/terminal/camera/default
Date: Dec 2014
KernelVersion: 4.0
Description: Default camera terminal descriptors
All attributes read only:
bmControls - bitmap specifying which controls are
supported for the video stream
wOcularFocalLength - the value of Locular
wObjectiveFocalLengthMax- the value of Lmin
wObjectiveFocalLengthMin- the value of Lmax
iTerminal - index of string descriptor
bAssocTerminal - id of the output terminal to which
this terminal is connected
wTerminalType - terminal type
bTerminalID - a non-zero id of this terminal
What: /config/usb-gadget/gadget/functions/uvc.name/control/processing
Date: Dec 2014
KernelVersion: 4.0
Description: Processing unit descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/processing/default
Date: Dec 2014
KernelVersion: 4.0
Description: Default processing unit descriptors
All attributes read only:
iProcessing - index of string descriptor
bmControls - bitmap specifying which controls are
supported for the video stream
wMaxMultiplier - maximum digital magnification x100
bSourceID - id of the terminal to which this unit is
connected
bUnitID - a non-zero id of this unit
What: /config/usb-gadget/gadget/functions/uvc.name/control/header
Date: Dec 2014
KernelVersion: 4.0
Description: Control header descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/control/header/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific control header descriptors
dwClockFrequency
bcdUVC
What: /config/usb-gadget/gadget/functions/uvc.name/streaming
Date: Dec 2014
KernelVersion: 4.0
Description: Streaming descriptors
All attributes read only:
bInterfaceNumber - USB interface number for this
streaming interface
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/class
Date: Dec 2014
KernelVersion: 4.0
Description: Streaming class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/class/ss
Date: Dec 2014
KernelVersion: 4.0
Description: Super speed streaming class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/class/hs
Date: Dec 2014
KernelVersion: 4.0
Description: High speed streaming class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/class/fs
Date: Dec 2014
KernelVersion: 4.0
Description: Full speed streaming class descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/color_matching
Date: Dec 2014
KernelVersion: 4.0
Description: Color matching descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/color_matching/default
Date: Dec 2014
KernelVersion: 4.0
Description: Default color matching descriptors
All attributes read only:
bMatrixCoefficients - matrix used to compute luma and
chroma values from the color primaries
bTransferCharacteristics- optoelectronic transfer
characteristic of the source picutre,
also called the gamma function
bColorPrimaries - color primaries and the reference
white
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/mjpeg
Date: Dec 2014
KernelVersion: 4.0
Description: MJPEG format descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/mjpeg/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific MJPEG format descriptors
All attributes read only,
except bmaControls and bDefaultFrameIndex:
bFormatIndex - unique id for this format descriptor;
only defined after parent header is
linked into the streaming class;
read-only
bmaControls - this format's data for bmaControls in
the streaming header
bmInterfaceFlags - specifies interlace information,
read-only
bAspectRatioY - the X dimension of the picture aspect
ratio, read-only
bAspectRatioX - the Y dimension of the picture aspect
ratio, read-only
bmFlags - characteristics of this format,
read-only
bDefaultFrameIndex - optimum frame index for this stream
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/mjpeg/name/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific MJPEG frame descriptors
bFrameIndex - unique id for this framedescriptor;
only defined after parent format is
linked into the streaming header;
read-only
dwFrameInterval - indicates how frame interval can be
programmed; a number of values
separated by newline can be specified
dwDefaultFrameInterval - the frame interval the device would
like to use as default
dwMaxVideoFrameBufferSize- the maximum number of bytes the
compressor will produce for a video
frame or still image
dwMaxBitRate - the maximum bit rate at the shortest
frame interval in bps
dwMinBitRate - the minimum bit rate at the longest
frame interval in bps
wHeight - height of decoded bitmap frame in px
wWidth - width of decoded bitmam frame in px
bmCapabilities - still image support, fixed frame-rate
support
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/uncompressed
Date: Dec 2014
KernelVersion: 4.0
Description: Uncompressed format descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/uncompressed/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific uncompressed format descriptors
bFormatIndex - unique id for this format descriptor;
only defined after parent header is
linked into the streaming class;
read-only
bmaControls - this format's data for bmaControls in
the streaming header
bmInterfaceFlags - specifies interlace information,
read-only
bAspectRatioY - the X dimension of the picture aspect
ratio, read-only
bAspectRatioX - the Y dimension of the picture aspect
ratio, read-only
bDefaultFrameIndex - optimum frame index for this stream
bBitsPerPixel - number of bits per pixel used to
specify color in the decoded video
frame
guidFormat - globally unique id used to identify
stream-encoding format
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/uncompressed/name/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific uncompressed frame descriptors
bFrameIndex - unique id for this framedescriptor;
only defined after parent format is
linked into the streaming header;
read-only
dwFrameInterval - indicates how frame interval can be
programmed; a number of values
separated by newline can be specified
dwDefaultFrameInterval - the frame interval the device would
like to use as default
dwMaxVideoFrameBufferSize- the maximum number of bytes the
compressor will produce for a video
frame or still image
dwMaxBitRate - the maximum bit rate at the shortest
frame interval in bps
dwMinBitRate - the minimum bit rate at the longest
frame interval in bps
wHeight - height of decoded bitmap frame in px
wWidth - width of decoded bitmam frame in px
bmCapabilities - still image support, fixed frame-rate
support
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/header
Date: Dec 2014
KernelVersion: 4.0
Description: Streaming header descriptors
What: /config/usb-gadget/gadget/functions/uvc.name/streaming/header/name
Date: Dec 2014
KernelVersion: 4.0
Description: Specific streaming header descriptors
All attributes read only:
bTriggerUsage - how the host software will respond to
a hardware trigger interrupt event
bTriggerSupport - flag specifying if hardware
triggering is supported
bStillCaptureMethod - method of still image caputre
supported
bTerminalLink - id of the output terminal to which
the video endpoint of this interface
is connected
bmInfo - capabilities of this video streaming
interface
What: /sys/class/udc/udc.name/device/gadget/video4linux/video.name/function_name
Date: May 2018
KernelVersion: 4.19
Description: UVC configfs function instance name
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