linux-kernel - Re: [PATCH v5 2/2] drm/tiny: add driver for Apple Touch Bars in x86 Macs

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Message-ID: <Z72jHeCG6-ByMyhh@smile.fi.intel.com>
Date: Tue, 25 Feb 2025 13:01:49 +0200
From: "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>
To: Aditya Garg <gargaditya08@...e.com>
Cc: "maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>,
	"tzimmermann@...e.de" <tzimmermann@...e.de>,
	"airlied@...il.com" <airlied@...il.com>,
	"simona@...ll.ch" <simona@...ll.ch>,
	Kerem Karabay <kekrby@...il.com>,
	Atharva Tiwari <evepolonium@...il.com>,
	Aun-Ali Zaidi <admin@...eit.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v5 2/2] drm/tiny: add driver for Apple Touch Bars in x86
 Macs

On Tue, Feb 25, 2025 at 10:48:53AM +0000, Aditya Garg wrote:
> > On 25 Feb 2025, at 4:17 PM, andriy.shevchenko@...ux.intel.com wrote:
> > On Tue, Feb 25, 2025 at 10:36:03AM +0000, Aditya Garg wrote:
> >>>> On 25 Feb 2025, at 4:03 PM, andriy.shevchenko@...ux.intel.com wrote:
> >>> On Tue, Feb 25, 2025 at 10:09:42AM +0000, Aditya Garg wrote:

...

> >>>> +static int appletbdrm_probe(struct usb_interface *intf,
> >>>> +                const struct usb_device_id *id)
> >>>> +{
> >>>> +    struct usb_endpoint_descriptor *bulk_in, *bulk_out;
> >>>> +    struct device *dev = &intf->dev;
> >>>> +    struct appletbdrm_device *adev;
> >>>> +    struct drm_device *drm;
> >>>> +    int ret;
> >>>> +
> >>>> +    ret = usb_find_common_endpoints(intf->cur_altsetting, &bulk_in, &bulk_out, NULL, NULL);
> >>>> +    if (ret) {
> >>>> +        drm_err(drm, "Failed to find bulk endpoints\n");
> >>> 
> >>> This is simply wrong (and in this case even lead to crash in some circumstances).
> >>> drm_err() may not be used here. That's my point in previous discussions.
> >>> Independently on the subsystem the ->probe() for the sake of consistency and
> >>> being informative should only rely on struct device *dev,
> >> 
> >> I'm not sure how drm_err works,
> > 
> > It's a macro.
> > 
> >> but struct drm_device does have a struct device *dev as well.
> > 
> > Yes, but only when it's initialized.
> > 
> >> Anyways, this is something I'll leave for Thomas to reply.
> > 
> > The code above is wrong independently on his reply :-)
> 
> I'm kinda stuck between contrasting views of 2 kernel maintainers lol,
> so I said let Thomas reply.

Sure. I also want him to clarify my question about potential drm_err_probe().

-- 
With Best Regards,
Andy Shevchenko