linux-kernel - Re: [PATCH 1/3] drm: add gem ttm helpers

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Message-ID: <20190807210853.GH7444@phenom.ffwll.local>
Date:   Wed, 7 Aug 2019 23:08:53 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] drm: add gem ttm helpers

On Wed, Aug 07, 2019 at 01:51:33PM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > > > > I don't think so.  drm_gem_dumb_map_offset() calls
> > > > > drm_gem_create_mmap_offset(), which I think is not correct for ttm
> > > > > objects because ttm_bo_init() handles vma_node initialization.
> 
> > Ok I looked again, and your ttm version seems to exactly match
> > drm_gem_dumb_map_offset(),
> 
> No.  The difference outlined above is still there.  See also v2 which
> adds an comment saying so.

Creating an mmap offset is idempotent. Otherwise the gem version would
already blow up real bad, since it's getting called multiple times by
userspace already.

So I still think ttm isn't special here, how did this blow up when you
tried?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch