linux-kernel - Re: [PATCH 2/2] media: i2c: Add GT97xx VCM driver

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Message-ID: <ZhzWdmg8cc1tgtNc@kekkonen.localdomain>
Date: Mon, 15 Apr 2024 07:25:42 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Zhi Mao <zhi.mao@...iatek.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Hans Verkuil <hverkuil-cisco@...all.nl>,
	Hans de Goede <hdegoede@...hat.com>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Alain Volmat <alain.volmat@...s.st.com>,
	Paul Elder <paul.elder@...asonboard.com>,
	Mehdi Djait <mehdi.djait@...tlin.com>,
	Bingbu Cao <bingbu.cao@...el.com>, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, shengnan.wang@...iatek.com,
	yaya.chang@...iatek.com, yunkec@...omium.org, 10572168@...com
Subject: Re: [PATCH 2/2] media: i2c: Add GT97xx VCM driver

Hi Andy,

On Fri, Apr 12, 2024 at 04:43:43PM +0300, Andy Shevchenko wrote:
> On Fri, Apr 12, 2024 at 12:39 PM Sakari Ailus
> <sakari.ailus@...ux.intel.com> wrote:
> > On Wed, Apr 10, 2024 at 07:00:02PM +0300, Andy Shevchenko wrote:
> > > > +static int gt97xx_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> > > > +{
> > > > +       return pm_runtime_resume_and_get(sd->dev);
> > > > +}
> > > > +
> > > > +static int gt97xx_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> > > > +{
> > > > +       return pm_runtime_put(sd->dev);
> > > > +}
> > >
> > > Hmm... Shouldn't v4l2 take care about these (PM calls)?
> >
> > Ideally yes. We don't have a good mechanism for this at the moment as the
> > lens isn't part of the image pipeline. Non-data links may be used for this
> > in the future but that's not implemented yet.
> 
> Aren't you using devlinks? It was designed exactly to make sure that
> the PM chain of calls goes in the correct order.

Device links are already used by the IPU bridge, but in the other
direction: the VCM requires the sensor to be powered up in this case.

-- 
Regards,

Sakari Ailus