linux-kernel - Re: [PATCH v4 2/3] drm: Add support for the LogiCVC display controller

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Date:   Fri, 3 Apr 2020 11:13:44 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v4 2/3] drm: Add support for the LogiCVC display
 controller

Hi Sam,

On Sat 04 Jan 20, 20:20, Sam Ravnborg wrote:
> Good looking driver. Well structured in a number of relevant files.
> A few comments in the following.
> Some parts I fail to follow - due to my lack of DRM knowledge.
> So all in all - only trivial comments.

Thanks for the review and the friendly feedback!

> With these fixed you can add:
> Acked-by: Sam Ravnborg <sam@...nborg.org>

I'll take most of your suggestions in for the next version and there's just one
point where I disagree:

> > +struct logicvc_drm {
> > +	const struct logicvc_drm_caps *caps;
> > +	struct logicvc_drm_config config;
> > +	struct drm_device *drm;
> Modern drm drivers are expected to embed drm_device.
> See example in drm_drv.c

Well, I see lots of modern drivers that use drm_dev_alloc, including vc4 that
I took as a reference. 

My understanding is that embedding the struct is a recommendation but
drm_dev_alloc is still quite valid and that the choice is left open.
Quoting drm_drv.c:

 * It is recommended that drivers embed &struct drm_device into their own device
 * structure.
 *
 * Drivers that do not want to allocate their own device struct
 * embedding &struct drm_device can call drm_dev_alloc() instead.

In my case, I like the fact that drm_dev_alloc correctly wraps drm_dev_init
and drmm_add_final_kfree (and I'd rather not add & all around unless I'm
obliged to ;)

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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