linux-kernel - Re: [v1,1/3] drm/panel: ili9341: Correct use of device property APIs

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Date: Thu, 2 May 2024 20:28:51 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Sam Ravnborg <sam@...nborg.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [v1,1/3] drm/panel: ili9341: Correct use of device property APIs

On Fri, May 03, 2024 at 12:25:17AM +0800, Sui Jingfeng wrote:
> On 2024/5/2 16:32, Andy Shevchenko wrote:
> > On Wed, May 01, 2024 at 12:27:14AM +0800, Sui Jingfeng wrote:
> > > On 2024/4/30 22:13, Andy Shevchenko wrote:
> > > > On Fri, Apr 26, 2024 at 05:13:43AM +0800, Sui Jingfeng wrote:

..

> > > > the former might be subdivided to "is it swnode backed or real fwnode one?"
> > > > 
> > > Yeah,
> > > On non-DT cases, it can be subdivided to swnode backed case and ACPI fwnode backed case.
> > > 
> > >   - For swnode backed case: the device_get_match_data() don't has a implemented backend.
> > >   - For ACPI fwnode backed case: the device_get_match_data() has a implemented backend.
> > > 
> > > But the driver has *neither* software node support
> > True.
> > 
> > > nor ACPI support,
> > Not true.
> 
> Why this is not true? Are you means that the panel-ilitek-ili9341 driver has ACPI support?

That's the idea (as far as I see the copy of the code from tinyDRM),
but broken over the copy'n'paste. This patch rectifies that to be
in align with the original code, which *does* support ACPI.

> I'm asking because I don't see struct acpi_device_id related stuff in that source file,
> am I miss something?

Yes, you are. I leave it for you to research.

> > So, slow down and take your time to get into the code and understand how it works.
> > 
> > > so that the rotation property can not get and ili9341_dpi_probe() will fails.
> > > So in total, this is not a 100% correct use of device property APIs.
> > > 
> > > But I'm fine that if you want to leave(ignore) those less frequent use cases temporarily,
> > > there may have programmers want to post patches, to complete the missing in the future.
> > > 
> > > So, there do have some gains on non-DT cases.
> > > 
> > >   - As you make it be able to compiled on X86 with the drm-misc-defconfig.
> > >   - You cleanup the code up (at least patch 2 in this series is no obvious problem).
> > >   - You allow people to modprobe it, and maybe half right and half undefined.
> > > 
> > > But you do helps moving something forward, so congratulations for the wake up.

-- 
With Best Regards,
Andy Shevchenko