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Subject: Re: [PATCH v5 5/8] iio: core: Add new DMABUF interface
 infrastructure
From: Paul Cercueil <paul@crapouillou.net>
To: Christian =?ISO-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>, 
	Jonathan Cameron
	 <jic23@kernel.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>, Sumit Semwal
 <sumit.semwal@linaro.org>,  Vinod Koul <vkoul@kernel.org>, Jonathan Corbet
 <corbet@lwn.net>, linux-doc@vger.kernel.org,  linux-kernel@vger.kernel.org,
 dmaengine@vger.kernel.org,  linux-iio@vger.kernel.org,
 linux-media@vger.kernel.org,  dri-devel@lists.freedesktop.org,
 linaro-mm-sig@lists.linaro.org, Nuno =?ISO-8859-1?Q?S=E1?=
 <noname.nuno@gmail.com>, Michael Hennerich <Michael.Hennerich@analog.com>
Date: Mon, 29 Jan 2024 15:15:08 +0100
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Le lundi 29 janvier 2024 =C3=A0 14:32 +0100, Paul Cercueil a =C3=A9crit=C2=
=A0:
> Le lundi 29 janvier 2024 =C3=A0 14:17 +0100, Christian K=C3=B6nig a =C3=
=A9crit=C2=A0:
> > Am 29.01.24 um 14:06 schrieb Paul Cercueil:
> > > Hi Christian,
> > >=20
> > > Le lundi 29 janvier 2024 =C3=A0 13:52 +0100, Christian K=C3=B6nig a =
=C3=A9crit=C2=A0:
> > > > Am 27.01.24 um 17:50 schrieb Jonathan Cameron:
> > > > > > > > +	iio_buffer_dmabuf_put(attach);
> > > > > > > > +
> > > > > > > > +out_dmabuf_put:
> > > > > > > > +	dma_buf_put(dmabuf);
> > > > > > > As below. Feels like a __free(dma_buf_put) bit of magic
> > > > > > > would
> > > > > > > be a
> > > > > > > nice to have.
> > > > > > I'm working on the patches right now, just one quick
> > > > > > question.
> > > > > >=20
> > > > > > Having a __free(dma_buf_put) requires that dma_buf_put is
> > > > > > first
> > > > > > "registered" as a freeing function using DEFINE_FREE() in
> > > > > > <linux/dma-
> > > > > > buf.h>, which has not been done yet.
> > > > > >=20
> > > > > > That would mean carrying a dma-buf specific patch in your
> > > > > > tree,
> > > > > > are you
> > > > > > OK with that?
> > > > > Needs an ACK from appropriate maintainer, but otherwise I'm
> > > > > fine
> > > > > doing
> > > > > so.=C2=A0 Alternative is to circle back to this later after this
> > > > > code is
> > > > > upstream.
> > > > Separate patches for that please, the autocleanup feature is so
> > > > new
> > > > that
> > > > I'm not 100% convinced that everything works out smoothly from
> > > > the
> > > > start.
> > > Separate patches is a given, did you mean outside this patchset?
> > > Because I can send a separate patchset that introduces scope-
> > > based
> > > management for dma_fence and dma_buf, but then it won't have
> > > users.
> >=20
> > Outside of the patchset, this is essentially brand new stuff.
> >=20
> > IIRC we have quite a number of dma_fence selftests and sw_sync
> > which
> > is=20
> > basically code inside the drivers/dma-buf directory only there for=20
> > testing DMA-buf functionality.
> >=20
> > Convert those over as well and I'm more than happy to upstream this
> > change.
>=20
> Well there is very little to convert there; you can use scope-based
> management when the unref is done in all exit points of the
> functional
> block, and the only place I could find that does that in drivers/dma-
> buf/ was in dma_fence_chain_enable_signaling() in dma-fence-chain.c.

Actually - not even that, since it doesn't call dma_fence_get() and
dma_fence_put() on the same fence.

So I cannot use it anywhere in drivers/dma-buf/.

-Paul