[media] move V4L2 clocks to a separate .rst file (b67b81d7) · Commits · 戴 / test

Documentation/media/kapi/v4l2-clocks.rst

0 → 100644

+29 −0

Original line number	Diff line number	Diff line
		V4L2 clocks
		-----------

		.. attention::

		This is a temporary API and it shall be replaced by the generic
		clock API, when the latter becomes widely available.

		Many subdevices, like camera sensors, TV decoders and encoders, need a clock
		signal to be supplied by the system. Often this clock is supplied by the
		respective bridge device. The Linux kernel provides a Common Clock Framework for
		this purpose. However, it is not (yet) available on all architectures. Besides,
		the nature of the multi-functional (clock, data + synchronisation, I2C control)
		connection of subdevices to the system might impose special requirements on the
		clock API usage. E.g. V4L2 has to support clock provider driver unregistration
		while a subdevice driver is holding a reference to the clock. For these reasons
		a V4L2 clock helper API has been developed and is provided to bridge and
		subdevice drivers.

		The API consists of two parts: two functions to register and unregister a V4L2
		clock source: v4l2_clk_register() and v4l2_clk_unregister() and calls to control
		a clock object, similar to the respective generic clock API calls:
		v4l2_clk_get(), v4l2_clk_put(), v4l2_clk_enable(), v4l2_clk_disable(),
		v4l2_clk_get_rate(), and v4l2_clk_set_rate(). Clock suppliers have to provide
		clock operations that will be called when clock users invoke respective API
		methods.

		It is expected that once the CCF becomes available on all relevant
		architectures this API will be removed.

Documentation/media/kapi/v4l2-core.rst

+1 −0

Original line number	Diff line number	Diff line
		@@ -9,6 +9,7 @@ Video2Linux devices
		v4l2-controls
		v4l2-device
		v4l2-fh
		v4l2-clocks
		v4l2-dv-timings
		v4l2-event
		v4l2-flash-led-class

Documentation/media/kapi/v4l2-framework.rst

+0 −25

Original line number	Diff line number	Diff line
		@@ -79,28 +79,3 @@ and the v4l2_fh struct keeps track of filehandle instances.
		The 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.

		V4L2 clocks
		-----------

		Many subdevices, like camera sensors, TV decoders and encoders, need a clock
		signal to be supplied by the system. Often this clock is supplied by the
		respective bridge device. The Linux kernel provides a Common Clock Framework for
		this purpose. However, it is not (yet) available on all architectures. Besides,
		the nature of the multi-functional (clock, data + synchronisation, I2C control)
		connection of subdevices to the system might impose special requirements on the
		clock API usage. E.g. V4L2 has to support clock provider driver unregistration
		while a subdevice driver is holding a reference to the clock. For these reasons
		a V4L2 clock helper API has been developed and is provided to bridge and
		subdevice drivers.

		The API consists of two parts: two functions to register and unregister a V4L2
		clock source: v4l2_clk_register() and v4l2_clk_unregister() and calls to control
		a clock object, similar to the respective generic clock API calls:
		v4l2_clk_get(), v4l2_clk_put(), v4l2_clk_enable(), v4l2_clk_disable(),
		v4l2_clk_get_rate(), and v4l2_clk_set_rate(). Clock suppliers have to provide
		clock operations that will be called when clock users invoke respective API
		methods.

		It is expected that once the CCF becomes available on all relevant
		architectures this API will be removed.

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