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

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Message-ID: <Z72foRL3diil9icd@smile.fi.intel.com>
Date: Tue, 25 Feb 2025 12:46:57 +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 10:36:03AM +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 :-)

-- 
With Best Regards,
Andy Shevchenko