Re: [PATCH v2] media: i2c: ov5640: Implement get_mbus_config

From: Francesco Dolcini <francesco@dolcini.it>
To: Jacopo Mondi <jacopo.mondi@ideasonboard.com>,
	Aishwarya Kothari <aishwarya.kothari@toradex.com>
Cc: Francesco Dolcini <francesco@dolcini.it>,
	Sakari Ailus <sakari.ailus@iki.fi>,
	Marcel Ziswiler <marcel@ziswiler.com>,
	linux-media@vger.kernel.org,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	kernel@pengutronix.de,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Francesco Dolcini <francesco.dolcini@toradex.com>,
	Marcel Ziswiler <marcel.ziswiler@toradex.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Steve Longerbeam <slongerbeam@gmail.com>,
	linux-kernel@vger.kernel.org,
	Marco Felsch <m.felsch@pengutronix.de>
Subject: Re: [PATCH v2] media: i2c: ov5640: Implement get_mbus_config
Date: Mon, 20 Mar 2023 12:13:38 +0100	[thread overview]
Message-ID: <ZBg/4gkKWBMtw5a9@francesco-nb.int.toradex.com> (raw)
In-Reply-To: <20230320084844.tdjiv6kaxcosiwm2@uno.localdomain>

On Mon, Mar 20, 2023 at 09:48:44AM +0100, Jacopo Mondi wrote:
> On Tue, Mar 14, 2023 at 01:59:06PM +0100, Francesco Dolcini wrote:
> > On Tue, Mar 14, 2023 at 02:45:53PM +0200, Sakari Ailus wrote:
> > > On Tue, Mar 14, 2023 at 01:32:16PM +0100, Francesco Dolcini wrote:
> > > > On Tue, Mar 14, 2023 at 02:13:46PM +0200, Sakari Ailus wrote:
> > > > > On Mon, Mar 06, 2023 at 07:36:49AM +0100, Marcel Ziswiler wrote:
> > > > > > From: Aishwarya Kothari <aishwarya.kothari@toradex.com>
> > > > > >
> > > > > > Implement the introduced get_mbus_config operation to report the
> > > > > > config of the MIPI CSI-2, BT.656 and Parallel interface.
> > > > > >
> > > > > > Signed-off-by: Aishwarya Kothari <aishwarya.kothari@toradex.com>
> > > > > > Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> > > > >
> > > > > What's the reasoning for this patch?
> > > >
> > > > Without this it's not possible to use it on i.MX6,
> > > > drivers/staging/media/imx/imx6-mipi-csi2.c requires it, some more
> > > > details from Jacopo here [0].
> > > >
> > > > Everything used to work fine up to v5.18, after that kernel version
> > > > various changes broke it [1][2] (I assume you are pretty much aware of
> > > > the history here, you commented on a few emails).
> > > >
> > > > [0] https://lore.kernel.org/all/20230128100611.7ulsfqqqgscg54gy@uno.localdomain/
> > > > [1] https://lore.kernel.org/all/081cc2d3-1f3a-6c14-6dc7-53f976be7b2b@gmail.com/
> > > > [2] https://lore.kernel.org/all/cacfe146-101b-35b3-5f66-1a1cabfd342f@gmail.com/
> > > >
> > > > > Drivers that don't have e.g. dynamic lane configuration shouldn't need to
> > > > > implement get_mbus_config.
> > >
> > > Not even for staging drivers. The driver should be fixed to get that
> > > information from the endpoint instead.
> >
> > This seems exactly the opposite of what commit
> > 7318abface48 ("media: imx: Use get_mbus_config instead of parsing upstream DT endpoints")
> > did.
> >
> > Given that I am somehow confused, but I am not that familiar with this
> > subsystem, so I guess this is expected :-). Can someone provide some
> > additional hint here?
> >
> To be honest my understanding is that this patch has always been
> needed to work on imx6 and this is not a regression but something that
> was kept as an out-of-tree patch downstream. Is this correct or is
> this a regression ?

I confirm that v5.18 was/is fine.  Aishwarya: correct? In the end you
tested it, not me :-)

Francesco