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

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Message-ID: <Z73ExmFOcOoozjxS@smile.fi.intel.com>
Date: Tue, 25 Feb 2025 15:25:26 +0200
From: "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>
To: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Aditya Garg <gargaditya08@...e.com>,
	"maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>,
	"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 12:58:17PM +0100, Thomas Zimmermann wrote:
> Am 25.02.25 um 11:33 schrieb andriy.shevchenko@...ux.intel.com:
> > 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,
> 
> That's never going to work with DRM. There's so much code in a DRM probe
> function that uses the DRM error functions.

> This specific instance here is wrong, as the drm pointer hasn't been
> initialized. But as soon as it is, it's much better to use drm_err() and
> friends. It will do the right thing and give consistent output across
> drivers.

Okay and my question was how is it possible to create drm_err_probe() for such
cases?

> > > +		return ret;
> > > +	}

-- 
With Best Regards,
Andy Shevchenko