linux-kernel - Re: [PATCH RFC v3] media: i2c: mt9p031: add OF support

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Message-ID: <2897565.OjqREpRvoz@avalon>
Date:	Tue, 14 May 2013 00:59:27 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	Prabhakar Lad <prabhakar.csengg@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	LMML <linux-media@...r.kernel.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	DLOS <davinci-linux-open-source@...ux.davincidsp.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	LKML <linux-kernel@...r.kernel.org>,
	Sakari Ailus <sakari.ailus@....fi>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH RFC v3] media: i2c: mt9p031: add OF support

Hi Sascha,

On Monday 13 May 2013 12:46:04 Sascha Hauer wrote:
> On Wed, May 08, 2013 at 12:37:29PM +0200, Laurent Pinchart wrote:
> > Hi Prabhakar,
> > 
> > On Wednesday 08 May 2013 10:19:57 Prabhakar Lad wrote:
> > > On Wed, May 8, 2013 at 7:32 AM, Laurent Pinchart wrote:
> > > > On Tuesday 07 May 2013 15:10:36 Prabhakar Lad wrote:
> > > >> On Mon, May 6, 2013 at 8:29 PM, Prabhakar Lad wrote:
> > > >> > On Fri, May 3, 2013 at 8:04 PM, Arnd Bergmann wrote:
> > > >> >> On Friday 03 May 2013, Prabhakar Lad wrote:
> > > >> > [snip]
> > > >> > 
> > > >> >>> +}
> > > >> >> 
> > > >> >> Ok, good.
> > > >> >> 
> > > >> >>> @@ -955,7 +998,17 @@ static int mt9p031_probe(struct i2c_client
> > > >> >>> *client,
> > > >> >>> 
> > > >> >>>         mt9p031->pdata = pdata;
> > > >> >>>         mt9p031->output_control = MT9P031_OUTPUT_CONTROL_DEF;
> > > >> >>>         mt9p031->mode2 = MT9P031_READ_MODE_2_ROW_BLC;
> > > >> >>> 
> > > >> >>> -       mt9p031->model = did->driver_data;
> > > >> >>> +
> > > >> >>> +       if (!client->dev.of_node) {
> > > >> >>> +               mt9p031->model = (enum
> > > >> >>> mt9p031_model)did->driver_data;
> > > >> >>> +       } else {
> > > >> >>> +               const struct of_device_id *of_id;
> > > >> >>> +
> > > >> >>> +               of_id =
> > > >> >>> of_match_device(of_match_ptr(mt9p031_of_match),
> > > >> >>> +                                       &client->dev);
> > > >> >>> +               if (of_id)
> > > >> >>> +                       mt9p031->model = (enum
> > > >> >>> mt9p031_model)of_id->data;
> > > >> >>> +       }
> > > >> >>> 
> > > >> >>>         mt9p031->reset = -1;
> > > >> >> 
> > > >> >> Is this actually required? I thought the i2c core just compared
> > > >> >> the
> > > >> >> part of the "compatible" value after the first comma to the
> > > >> >> string, so
> > > >> >> "mt9p031->model = (enum mt9p031_model)did->driver_data" should
> > > >> >> work
> > > >> >> in both cases.
> 
> At least on v3.8 I just checked that 'did' is indeed NULL for the
> devicetree case. Also I see no indication that i2c starts comparing
> after the first comma in the string.
> 
> > > >> > I am OK with "mt9p031->model = (enum
> > > >> > mt9p031_model)did->driver_data"
> > > >> > but I see still few drivers doing this, I am not sure for what
> > > >> > reason.
> > > >> > If everyone is OK with it I can drop the above change.
> > > >> 
> > > >> My bad, while booting with DT the i2c_device_id ie did in this case
> > > >> will
> > > >> be NULL, so the above changes are required :-)
> > > > 
> > > > I've just tested your patch, and did isn't NULL when booting my
> > > > Beagleboard with DT (on v3.9-rc5).
> > > 
> > > I am pretty much sure you tested it compatible property as
> > > "aptina,mt9p031"
> > > if the compatible property is set to "aptina,mt9p031m" the did will be
> > > NULL.> 
> > I've tested both :-)
> 
> Sorry to nag, but did you use "aptina,mt9p031[m]" as a compatible string or
> did you use "mt9p031[m]". With "aptina,..." 'did' should really be NULL.

I've used "aptina,mt9p031[m]".

Please see the of_modalias_node() call in of_i2c_register_devices() 
(drivers/of/of-i2c.c), that's where the I2C device type name should be 
initialized.

-- 
Regards,

Laurent Pinchart

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