linux-kernel - Re: [PATCH v2] software node: Implement device_get_match

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Date: Wed, 24 Apr 2024 19:44:50 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Sui Jingfeng <sui.jingfeng@...ux.dev>, dri-devel@...ts.freedesktop.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v2] software node: Implement device_get_match_data fwnode
 callback

On Wed, Apr 24, 2024 at 07:34:54PM +0300, Dmitry Baryshkov wrote:
> On Wed, Apr 24, 2024 at 05:52:03PM +0300, Andy Shevchenko wrote:
> > On Wed, Apr 24, 2024 at 04:34:39PM +0300, Dmitry Baryshkov wrote:
> > > On Wed, 24 Apr 2024 at 16:11, Andy Shevchenko
> > > <andriy.shevchenko@...ux.intel.com> wrote:
> > > > On Wed, Apr 24, 2024 at 12:37:16AM +0300, Dmitry Baryshkov wrote:
> > > > > On Wed, Apr 24, 2024 at 12:49:18AM +0800, Sui Jingfeng wrote:
> > > > > > On 2024/4/23 21:28, Andy Shevchenko wrote:
> > > > > > > On Tue, Apr 23, 2024 at 12:46:58AM +0800, Sui Jingfeng wrote:

..

> > > > > But let me throw an argument why this patch (or something similar) looks
> > > > > to be necessary.
> > > > >
> > > > > Both on DT and non-DT systems the kernel allows using the non-OF based
> > > > > matching. For the platform devices there is platform_device_id-based
> > > > > matching.
> > > > >
> > > > > Currently handling the data coming from such device_ids requires using
> > > > > special bits of code, e.g. platform_get_device_id(pdev)->driver_data to
> > > > > get the data from the platform_device_id. Having such codepaths goes
> > > > > against the goal of unifying DT and non-DT paths via generic property /
> > > > > fwnode code.
> > > > >
> > > > > As such, I support Sui's idea of being able to use device_get_match_data
> > > > > for non-DT, non-ACPI platform devices.
> > > >
> > > > I'm not sure I buy this. We have a special helpers based on the bus type to
> > > > combine device_get_match_data() with the respective ID table crawling, see
> > > > the SPI and I²C cases as the examples.
> > > 
> > > I was thinking that we might be able to deprecate these helpers and
> > > always use device_get_match_data().
> > 
> > True, but that is orthogonal to swnode match_data support, right?
> > There even was (still is?) a patch series to do something like a new
> > member to struct device_driver (? don't remember) to achieve that.
> 
> Maybe the scenario was not properly described in the commit message, or
> maybe I missed something. The usecase that I understood from the commit
> message was to use instatiated i2c / spi devices, which means
> i2c_device_id / spi_device_id. The commit message should describe why
> the usecase requires using 'compatible' property and swnode. Ideally it
> should describe how these devices are instantiated at the first place.

Yep. I also do not clearly understand the use case and why we need to have
a board file, because the swnodes all are about board files that we must not
use for the new platforms.

-- 
With Best Regards,
Andy Shevchenko