linux-kernel - Re: [PATCH] media: i2c: ov5645: Add virtual

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Message-ID: <20200310124301.GD5379@paasikivi.fi.intel.com>
Date:   Tue, 10 Mar 2020 14:43:01 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-media <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Jacopo Mondi <jacopo@...ndi.org>
Subject: Re: [PATCH] media: i2c: ov5645: Add virtual_channel module parameter

On Tue, Mar 10, 2020 at 11:17:10AM +0000, Lad, Prabhakar wrote:
> Hi Sakari,
> 
> On Fri, Mar 6, 2020 at 10:18 AM Lad, Prabhakar
> <prabhakar.csengg@...il.com> wrote:
> >
> > Hi Sakari,
> >
> > On Thu, Mar 5, 2020 at 11:43 AM Sakari Ailus
> > <sakari.ailus@...ux.intel.com> wrote:
> > >
> > > Hi Prabhakar,
> > >
> > > On Fri, Feb 28, 2020 at 04:41:26PM +0000, Lad Prabhakar wrote:
> > > > OV5645 can operate in virtual channel 0-3 in CSI2 interfaces, this patch
> > > > adds support for module parameter virtual_channel to select the required
> > > > channel. By default OV5645 operates in virtual channel 0.
> > >
> > > What's your use case for different virtual channels?
> > >
> > Just ability to switch to different virtual channel, based on ov5640
> > driver. The rcar-csi2
> > has capability to capture  from multiple channels so that we can
> > capture simultaneously
> > from two sensors.
> >
> Any thoughts on how this could be handled ?

A module parameter to support sending the pixel data on virtual channels is
certainly a hack. You couldn't support the same kind of sensors with
different virtual channel configuration in a deterministic way nor the
receiver would have an ability to verify the hardware is properly
configured.

The multiplexed streams patchset (subject "[PATCH v3 00/31] v4l: add
support for multiplexed streams" on LMML) adds support for CSI-2 virtual
channels and data types. It's been a while since a version of that was
posted though.

Jacopo, what are your plans regarding that set?

-- 
Kind regards,

Sakari Ailus