linux-kernel - Re: [PATCH] media: i2c: rdacm2x: properly set subdev entity function

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Date:   Wed, 09 Mar 2022 10:07:39 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Laurentiu Palcu <laurentiu.palcu@....nxp.com>
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: i2c: rdacm2x: properly set subdev entity function

Quoting Laurentiu Palcu (2022-03-09 09:29:44)
> Hi Jacopo,
> 
> On Wed, Mar 09, 2022 at 09:43:11AM +0100, Jacopo Mondi wrote:
> > Hi Laurentiu,
> > 
> > On Tue, Mar 08, 2022 at 02:55:49PM +0200, Laurentiu Palcu wrote:
> > > The subdevice entity function was left unset, which produces a warning
> > > when probing the device:
> > >
> > > mxc-md bus@...00000:camera: Entity type for entity rdacm20 19-0051 was
> > > not initialized!
> > >
> > > Also, set the entity flags to MEDIA_ENT_FL_DEFAULT instead of
> > > MEDIA_ENT_F_CAM_SENSOR which will be used for entity's function instead.
> > >
> > > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
> > > ---
> > > Hi,
> > >
> > > Only tested the rdacm20 part but I believe rdacm21 should work as well.
> > >
> > > Cheers,
> > > laurentiu
> > >
> > >  drivers/media/i2c/rdacm20.c | 3 ++-
> > >  drivers/media/i2c/rdacm21.c | 3 ++-
> > >  2 files changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/i2c/rdacm20.c b/drivers/media/i2c/rdacm20.c
> > > index 025a610de893..ea5b7d5151ee 100644
> > > --- a/drivers/media/i2c/rdacm20.c
> > > +++ b/drivers/media/i2c/rdacm20.c
> > > @@ -611,7 +611,8 @@ static int rdacm20_probe(struct i2c_client *client)
> > >             goto error_free_ctrls;
> > >
> > >     dev->pad.flags = MEDIA_PAD_FL_SOURCE;
> > > -   dev->sd.entity.flags |= MEDIA_ENT_F_CAM_SENSOR;
> > > +   dev->sd.entity.flags |= MEDIA_ENT_FL_DEFAULT;
> > 
> > I'm not sure if setting the DEFAULT flag is right:
> > 
> >  * %MEDIA_ENT_FL_DEFAULT
> >  *    indicates the default entity for a given type.
> >  *    This can be used to report the default audio and video devices or the
> >  *    default camera sensor.
> > 
> > In a typical setup there will be several RDACM2x in use, marking all
> > of them as "default" seems not right (if I understood the flag
> > description right).
> 
> My initial thought was to not set the entity flags at all. However,
> since the old code had the flags set to MEDIA_ENT_F_CAM_SENSOR which is,
> essentially, 0x20001, setting it to MEDIA_ENT_FL_DEFAULT (1 << 0) would
> mean, basically, the same thing and would not affect existing user apps
> that might already probe that flag... Removing the flag now might
> potentially break existing apps. :/
> 
> Are there any other opinions on this one?

I don't think it's right to add an incorrect flag, and I don't think any
application should have been relying on this.

The only place an application should check for MEDIA_ENT_F_CAM_SENSOR is
in the entity function.

--
Kieran


> > 
> > 
> > > +   dev->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
> > 
> > This seems right, and it's probably worth a Fixes tag?
> 
> I'll send a v2 with the Fixes tag which I meant to add but totally
> forgot...
> 
> Cheers,
> Laurentiu
> 
> > 
> > Thanks
> >    j
> > 
> > >     ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> > >     if (ret < 0)
> > >             goto error_free_ctrls;
> > > diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> > > index 12ec5467ed1e..be89bd43e88b 100644
> > > --- a/drivers/media/i2c/rdacm21.c
> > > +++ b/drivers/media/i2c/rdacm21.c
> > > @@ -583,7 +583,8 @@ static int rdacm21_probe(struct i2c_client *client)
> > >             goto error_free_ctrls;
> > >
> > >     dev->pad.flags = MEDIA_PAD_FL_SOURCE;
> > > -   dev->sd.entity.flags |= MEDIA_ENT_F_CAM_SENSOR;
> > > +   dev->sd.entity.flags |= MEDIA_ENT_FL_DEFAULT;
> > > +   dev->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
> > >     ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> > >     if (ret < 0)
> > >             goto error_free_ctrls;
> > > --
> > > 2.33.0
> > >