linux-kernel - Re: [PATCH v1 1/1] media: i2c: rdacm2x: Make use of device properties

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Message-ID: <20250331162739.GG14432@pendragon.ideasonboard.com>
Date: Mon, 31 Mar 2025 19:27:39 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	acopo Mondi <jacopo+renesas@...ndi.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH v1 1/1] media: i2c: rdacm2x: Make use of device properties

On Mon, Mar 31, 2025 at 07:22:27PM +0300, Andy Shevchenko wrote:
> On Mon, Mar 31, 2025 at 06:34:35PM +0300, Laurent Pinchart wrote:
> > On Mon, Mar 31, 2025 at 03:23:21PM +0300, Andy Shevchenko wrote:
> > > On Mon, Mar 31, 2025 at 03:07:48PM +0300, Laurent Pinchart wrote:
> > > > On Mon, Mar 31, 2025 at 09:16:36AM +0100, Kieran Bingham wrote:
> > > > > Quoting Andy Shevchenko (2025-03-31 08:34:35)
> > > > > > Convert the module to be property provider agnostic and allow
> > > > > > it to be used on non-OF platforms.
> > > > > 
> > > > > Looks reasonable to me.
> > > > 
> > > > Is that going to work out of the box though ? The calls below read the
> > > > "reg" property to get the device I2C addresses. AFAIK, ACPI handles I2C
> > > > addresses using ACPI-specific methods.
> > > > 
> > > > Andy, have you tested this patch on an ACPI system ?
> > > 
> > > Only compile-tested. But you are right, this is something different here
> > > between OF and ACPI.
> > > 
> > > I can rephrase the commit message to just point out that fwnode.h shouldn't
> > > be in the drivers and either converting to device property in an assumption
> > > that later it can be easier to support non-OF cases, or using of.h.
> > 
> > I wasn't aware that fwnode.h shouldn't be used in drivers, could you
> > explain that ?
> 
> The fwnode.h provides the data types and definitions that are meant
> to be used by the fwnode / device property API providers. The leaf drivers
> shouldn't have any business with those definitions. Everything the drivers
> need should be provided via property.h. property.h guarantees the necessary
> data types to be visible to the users, when required (mostly think of
> struct fwnode_reference_args). Yes, I am aware of v4l2-fwnode.h and it seems
> it falls into the category of special device property API provider.
> 
> > If this patch is part of an effort to eliminate usage of some APIs from
> > all drivers, I'm fine with it. Otherwise, I'm not sure it's worth
> > modifying the driver.
> 
> These drivers basically include the wrong header.
> If you insist, I can patch fwnode.h to add a comment summarizing the above.

No, it's fine. I mixed fwnode.h and property.h when writing my previous
reply, but I don't think it's a matter of lack of documentation, more
likely lack of sleep :-)

-- 
Regards,

Laurent Pinchart