usb: gadget: uvc: Make bmControls attr read/write

[linux-2.6-block.git] / Documentation / usb / gadget_uvc.rst

diff --git a/Documentation/usb/gadget_uvc.rst b/Documentation/usb/gadget_uvc.rst
index 6d22faceb1a0b309c9502aad2629d512cb90a6b4..62bd81ba3dd1fe6f7426eb58baac2e62360fdc0d 100644 (file)
--- a/Documentation/usb/gadget_uvc.rst
+++ b/Documentation/usb/gadget_uvc.rst
@@ -275,6 +275,34 @@ out with 0x00, for example:
 
 bNrInPins and baSourceID function in the same way.
 
+Configuring Supported Controls for Camera Terminal and Processing Unit
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Camera Terminal and Processing Units in the UVC chain also have bmControls
+attributes which function similarly to the same field in an Extension Unit.
+Unlike XUs however, the meaning of the bitflag for these units is defined in
+the UVC specification; you should consult the "Camera Terminal Descriptor" and
+"Processing Unit Descriptor" sections for an enumeration of the flags.
+
+.. code-block:: bash
+
+        # Set the Processing Unit's bmControls, flagging Brightness, Contrast
+        # and Hue as available controls:
+        echo 0x05 > $FUNCTION/control/processing/default/bmControls
+
+        # Set the Camera Terminal's bmControls, flagging Focus Absolute and
+        # Focus Relative as available controls:
+        echo 0x60 > $FUNCTION/control/terminal/camera/default/bmControls
+
+If you do not set these fields then by default the Auto-Exposure Mode control
+for the Camera Terminal and the Brightness control for the Processing Unit will
+be flagged as available; if they are not supported you should set the field to
+0x00.
+
+Note that the size of the bmControls field for a Camera Terminal or Processing
+Unit is fixed by the UVC specification, and so the bControlSize attribute is
+read-only here.
+
 Custom Strings Support
 ~~~~~~~~~~~~~~~~~~~~~~