Hi Sakari,

On Tue, 2017-02-07 at 22:46 +0200, Sakari Ailus wrote:

Hi Steve,

On Fri, Jan 06, 2017 at 06:11:31PM -0800, Steve Longerbeam wrote:

quoted

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 <redacted>
---
 .../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 ?

What do you mean? Should we add the optional bus-width property to
describe the bit width of the parallel bus even though the driver
doesn't care about any of the properties?

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>

[Added Sebastian do Cc:]

Yes, this is essentially the same driver, except that this driver also
handles MMIO-bitfield controlled muxes, and that the actual physical bus
(which the drivers currently don't care about) is MIPI CSI-2 in the
other case, and parallel this one.
They should probably be combined, or maybe split into two separate
drivers (MMIO controlled mux, GPIO controlled switch), possibly using
the same v4l2_subdev boilerplate.

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.

Yes, that seems to be necessary, as certainly we can't configure the mux
output bus parameters in DT to a fixed setting.

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

regards
Philipp