Re: [PATCH] drm/test/shmem: set a DMA mask for the mock device

From: Maxime Ripard <mripard@kernel.org>
To: Marco Pagani <marpagan@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	 Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>,
	 Daniel Vetter <daniel@ffwll.ch>,
	Guenter Roeck <linux@roeck-us.net>,
	 dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/test/shmem: set a DMA mask for the mock device
Date: Tue, 27 Feb 2024 17:25:46 +0100	[thread overview]
Message-ID: <ut2c26ig4e6pbtvszmfm34h4ev3oflwkz3mwkjtqaxlpethwfk@w3bnhg4iw4mn> (raw)
In-Reply-To: <03915b45-94f6-4863-8b11-d0e9dbd0283a@redhat.com>

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Hi,

On Mon, Feb 26, 2024 at 04:48:51PM +0100, Marco Pagani wrote:
> 
> On 2024-02-26 12:26, Maxime Ripard wrote:
> > Hi,
> > 
> > On Mon, Feb 26, 2024 at 12:00:27PM +0100, Marco Pagani wrote:
> >> Set a DMA mask for the mock device to avoid warnings generated in
> >> dma_map_sgtable().
> >>
> >> Reported-by: Guenter Roeck <linux@roeck-us.net>
> >> Signed-off-by: Marco Pagani <marpagan@redhat.com>
> > 
> > I've submitted last week this patch:
> > https://lore.kernel.org/all/20240221125324.718192-1-mripard@kernel.org/
> > 
> > Which should be equivalent, but fixes the issue for all users in the
> > tree.
> 
> Hi, thanks for letting me know. Fixing this issue for all DRM tests that were
> using platform devices through the helpers makes perfect sense to me. I'm a
> little more thoughtful about setting the mask for all KUnit tests that use fake
> devices since there may be specific use cases. Just one curiosity: why setting
> the default mask manually instead of using one of the dma_set_*() functions?

I think the (well, mine at least) expectation is that a kunit device is
a device that can be used in all reasonable contexts. Setting up the
device to be able to use any DMA-related function (or functions that use
a DMA-related function) makes total sense to me.

But it's a discussion worth having I think, so it would make sense to
raise this point with the kunit maintainers if you feel like it.

Maxime

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