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SubjectRe: [PATCH v3 13/24] platform: add video-multiplexer subdevice driver
Hi Steve,

On Fri, Jan 06, 2017 at 06:11:31PM -0800, Steve Longerbeam wrote:
> From: Philipp Zabel <p.zabel@pengutronix.de>
>
> This driver can handle SoC internal and external video bus multiplexers,
> controlled either by register bit fields or by a GPIO. The subdevice
> passes through frame interval and mbus configuration of the active input
> to the output side.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
>
> --
>
> - fixed a cut&paste error in vidsw_remove(): v4l2_async_register_subdev()
> should be unregister.
>
> - added media_entity_cleanup() and v4l2_device_unregister_subdev()
> to vidsw_remove().
>
> - there was a line left over from a previous iteration that negated
> the new way of determining the pad count just before it which
> has been removed (num_pads = of_get_child_count(np)).
>
> - Philipp Zabel has developed a set of patches that allow adding
> to the subdev async notifier waiting list using a chaining method
> from the async registered callbacks (v4l2_of_subdev_registered()
> and the prep patches for that). For now, I've removed the use of
> v4l2_of_subdev_registered() for the vidmux driver's registered
> callback. This doesn't affect the functionality of this driver,
> but allows for it to be merged now, before adding the chaining
> support.
>
> Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
> ---
> .../bindings/media/video-multiplexer.txt | 59 +++
> drivers/media/platform/Kconfig | 8 +
> drivers/media/platform/Makefile | 2 +
> drivers/media/platform/video-multiplexer.c | 472 +++++++++++++++++++++
> 4 files changed, 541 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/media/video-multiplexer.txt
> create mode 100644 drivers/media/platform/video-multiplexer.c
>
> diff --git a/Documentation/devicetree/bindings/media/video-multiplexer.txt b/Documentation/devicetree/bindings/media/video-multiplexer.txt
> new file mode 100644
> index 0000000..9d133d9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/video-multiplexer.txt
> @@ -0,0 +1,59 @@
> +Video Multiplexer
> +=================
> +
> +Video multiplexers allow to select between multiple input ports. Video received
> +on the active input port is passed through to the output port. Muxes described
> +by this binding may be controlled by a syscon register bitfield or by a GPIO.
> +
> +Required properties:
> +- compatible : should be "video-multiplexer"
> +- reg: should be register base of the register containing the control bitfield
> +- bit-mask: bitmask of the control bitfield in the control register
> +- bit-shift: bit offset of the control bitfield in the control register
> +- gpios: alternatively to reg, bit-mask, and bit-shift, a single GPIO phandle
> + may be given to switch between two inputs
> +- #address-cells: should be <1>
> +- #size-cells: should be <0>
> +- port@*: at least three port nodes containing endpoints connecting to the
> + source and sink devices according to of_graph bindings. The last port is
> + the output port, all others are inputs.
> +
> +Example:
> +
> +syscon {
> + compatible = "syscon", "simple-mfd";
> +
> + mux {

Could you use standardised properties for this, i.e. ones defined in
Documentation/devicetree/bindings/media/video-interfaces.txt ?

This is very similar to another patch "[PATCH] devicetree: Add video bus
switch" posted by Pavel Machek recently. The problem with that is also
similar than with this one: how to pass the CSI-2 bus configuration to the
receiver.

There's some discussion here:

<URL:http://www.spinics.net/lists/linux-media/msg109493.html>

As Laurent already suggested, I think we should have a common solution for
the problem that, besides conveying the bus parameters to the receiver, also
encompasses CSI-2 virtual channels and data types.

That would mean finishing the series of patches in the branch I believe
Laurent already quoted here.

> + compatible = "video-multiplexer";
> + /* Single bit (1 << 19) in syscon register 0x04: */
> + reg = <0x04>;
> + bit-mask = <1>;
> + bit-shift = <19>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + port@0 {
> + reg = <0>;
> +
> + mux_in0: endpoint {
> + remote-endpoint = <&video_source0_out>;
> + };
> + };
> +
> + port@1 {
> + reg = <1>;
> +
> + mux_in1: endpoint {
> + remote-endpoint = <&video_source1_out>;
> + };
> + };
> +
> + port@2 {
> + reg = <2>;
> +
> + mux_out: endpoint {
> + remote-endpoint = <&capture_interface_in>;
> + };
> + };
> + };
> +};

--
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi XMPP: sailus@retiisi.org.uk

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