linux-kernel - Re: [PATCH v3 8/9] media: i2c: ov5645: Don't return early on failures for s

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Date:   Wed, 26 Oct 2022 19:35:19 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Shawn Tu <shawnx.tu@...el.com>, devicetree@...r.kernel.org,
        Jacopo Mondi <jacopo@...ndi.org>, linux-kernel@...r.kernel.org,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        linux-renesas-soc@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v3 8/9] media: i2c: ov5645: Don't return early on
 failures for s_stream(0)

On 22-10-26, Lad, Prabhakar wrote:
> Hi Marco,
> 
> Thank you for the review.
> 
> On Wed, Oct 26, 2022 at 6:17 PM Marco Felsch <m.felsch@...gutronix.de> wrote:
> >
> > Hi Prabhakar,
> >
> > thanks for the patch, please see below my comments.
> >
> > On 22-10-26, Prabhakar wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >
> > > Make sure we dont stop the code flow in case of errors while stopping
> > > the stream and return the error code of the first error case if any.
> > >
> > > v4l2-core takes care of warning the user so no need to add a warning
> > > message in the driver.
> > >
> > > Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > ---
> > > v2->v3
> > > * Now propagating the first error code in case of failure.
> > >
> > > v1->v2
> > > * New patch
> > > ---
> > >  drivers/media/i2c/ov5645.c | 11 ++++++++---
> > >  1 file changed, 8 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/media/i2c/ov5645.c b/drivers/media/i2c/ov5645.c
> > > index eea3067ddc8b..5702a55607fc 100644
> > > --- a/drivers/media/i2c/ov5645.c
> > > +++ b/drivers/media/i2c/ov5645.c
> > > @@ -996,17 +996,22 @@ static int ov5645_s_stream(struct v4l2_subdev *subdev, int enable)
> > >               if (ret < 0)
> > >                       goto err_rpm_put;
> > >       } else {
> > > +             int stream_off_ret = 0;
> > > +
> > >               ret = ov5645_write_reg(ov5645, OV5645_IO_MIPI_CTRL00, 0x40);
> >
> > If this write failed..
> >
> > >               if (ret < 0)
> > > -                     return ret;
> > > +                     stream_off_ret = ret;
> > >
> > >               ret = ov5645_write_reg(ov5645, OV5645_SYSTEM_CTRL0,
> > >                                      OV5645_SYSTEM_CTRL0_STOP);
> >
> > why should this write be successful?
> >
> Indeed that will fail unless I have a lucky day ;-)
> 
> But it seemed to be an overkill for adding an additional check to see
> if the previous write succeeded. Do you think this will create an
> issue?

Why not just say?

	ret = ov5645_write_reg();
	if (ret < 0)
		goto out;

	...

	out:

	dev_pm_xxx();

	return ret;

Regards,
  Marco