Re: [PATCH v7 00/34] i.MX Media Driver

[Sakari Ailus]

Hi Hans,

On Mon, May 29, 2017 at 03:46:08PM +0200, Hans Verkuil wrote:
> Hi Steve,
> 
> On 05/25/2017 02:29 AM, Steve Longerbeam wrote:
> >In version 7:
> >
> >- video-mux: switched to Philipp's latest video-mux driver and updated
> >   bindings docs, that makes use of the mmio-mux framework.
> >
> >- mmio-mux: includes Philipp's temporary patch that adds mmio-mux support
> >   to video-mux driver, until mux framework is merged.
> >
> >- mmio-mux: updates to device tree from Philipp that define the i.MX6 mux
> >   devices and modifies the video-mux device to become a consumer of the
> >   video mmio-mux.
> >
> >- minor updates to Documentation/media/v4l-drivers/imx.rst.
> >
> >- ov5640: do nothing if entity stream count is greater than 1 in
> >   ov5640_s_stream().
> >
> >- Previous versions of this driver had not tested the ability to enable
> >   multiple independent streams, for instance enabling multiple output
> >   pads from the imx6-mipi-csi2 subdevice, or enabling both prpenc and
> >   prpvf outputs. Marek Vasut tested this support and reported issues
> >   with it.
> >
> >   v4l2_pipeline_inherit_controls() used the media graph walk APIs, but
> >   that walks both sink and source pads, so if there are multiple paths
> >   enabled to video capture devices, controls would be added to the wrong
> >   video capture device, and no controls added to the other enabled
> >   capture devices.
> >
> >   These issues have been fixed. Control inheritance works correctly now
> >   even with multiple enabled capture paths, and (for example)
> >   simultaneous capture from prpenc and prpvf works also, and each with
> >   independent scaling, CSC, and controls. For example prpenc can be
> >   capturing with a 90 degree rotation, while prpvf is capturing with
> >   vertical flip.
> >
> >   So the v4l2_pipeline_inherit_controls() patch has been dropped. The
> >   new version of control inheritance could be made generically available,
> >   but it would be more involved to incorporate it into v4l2-core.
> >
> >- A new function imx_media_fill_default_mbus_fields() is added to setup
> >   colorimetry at sink pads, and these are propagated to source pads.
> >
> >- Ensure that the current sink and source rectangles meet alignment
> >   restrictions before applying a new rotation control setting in
> >   prp-enc/vf subdevices.
> >
> >- Chain the s_stream() subdev calls instead of implementing a custom
> >   stream on/off function that attempts to call a fixed set of subdevices
> >   in a pipeline in the correct order. This also simplifies imx6-mipi-csi2
> >   subdevice, since the correct MIPI CSI-2 startup sequence can be
> >   enforced completely in s_stream(), and s_power() is no longer
> >   required. This also paves the way for more arbitrary OF graphs
> >   external to the i.MX6.
> >
> >- Converted the v4l2_subdev and media_entity ops structures to const.
> 
> What is the status as of v7?
> 
> From what I can tell patch 2/34 needs an Ack from Rob Herring, patches
> 4-14 are out of scope for the media subsystem, patches 20-25 and 27-34
> are all staging (so fine to be merged from my point of view).
> 
> I'm not sure if patch 26 (defconfig) should be applied while the imx
> driver is in staging. I would suggest that this patch is moved to the end
> of the series.
> 
> That leaves patches 15-19. I replied to patch 15 with a comment, patches
> 16-18 look good to me, although patches 17 and 18 should be combined to one
> patch since patch 17 won't compile otherwise. Any idea when the multiplexer is
> expected to be merged? (just curious)
> 
> I would really like to get this merged for 4.13, so did I miss anything?
> From what I can tell it is really just an Ack for patch 2/34.

The patchset re-initialises the control handler in the video node in its
media device link_setup callback, among other things. I don't think that
this as such should prevent including the driver in staging, but at the same
time my concern is what kind of guarantees can we give in terms of V4L2
framework support on things like this using the current API. I'd say "none".

If there's a need for this (there should not be, as the controls are exposed
to the user space through the sub-device nodes as the other drivers do), the
framework APIs need to be extended.

I think it'd be good to add a TODO file (such as the one in OMAP4ISS) as
part of the patchset that would include a list of things left to do so
they're not forgotten.

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@xxxxxx	XMPP: sailus@xxxxxxxxxxxxxx