linux-kernel - Re: [PATCH v3 1/4] drm: add pgprot callback to drm_gem_object

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Message-ID: <20191211131005.ojbnsu3rvorlgnof@sirius.home.kraxel.org>
Date:   Wed, 11 Dec 2019 14:10:05 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org, tzimmermann@...e.de,
        gurchetansingh@...omium.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/4] drm: add pgprot callback to drm_gem_object_funcs

> > +	/**
> > +	 * @pgprot:
> > +	 *
> > +	 * Tweak pgprot as needed, typically used to set cache bits.
> > +	 *
> > +	 * This callback is optional.
> > +	 *
> > +	 * If unset drm_gem_pgprot_wc() will be used.
> > +	 */
> > +	pgprot_t (*pgprot)(struct drm_gem_object *obj, pgprot_t prot);
> 
> I kinda prefer v1, mostly because this is a huge can of worms, and solving
> this properly is going to be real hard (and will necessarily involve
> dma-buf and dma-api and probably more). Charging ahead here just risks
> that we dig ourselves into a corner. You're v1 is maybe not the most
> clean, but just a few code bits here&there should be more flexible and
> easier to hack on and experiment around with.

Hmm.  Second vote for v1.

Problem with v1 is that it covers mmap() only, not vmap() ...

cheers,
  Gerd