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Message-ID: <35805dbb85496d3a27872c578158c695c8bbb6b5.camel@gmail.com>
Subject: Re: [PATCH v3 00/11] iio: new DMABUF based API, v3
From:   Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To:     Paul Cercueil <paul@crapouillou.net>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Vinod Koul <vkoul@kernel.org>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Christian =?ISO-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>
Cc:     linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
        dmaengine@vger.kernel.org, linux-media@vger.kernel.org
Date:   Tue, 04 Apr 2023 09:44:18 +0200
In-Reply-To: <20230403154800.215924-1-paul@crapouillou.net>
References: <20230403154800.215924-1-paul@crapouillou.net>
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On Mon, 2023-04-03 at 17:47 +0200, Paul Cercueil wrote:
> Hi Jonathan,
>=20
> Here's the v3 of my patchset that introduces a new interface based on
> DMABUF objects to complement the fileio API, and adds write() support to
> the existing fileio API.
>=20
> It changed quite a lot since V2; the IIO subsystem is now just a DMABUF
> importer, and all the complexity related to handling creation, deletion
> and export of DMABUFs (including DMA mapping etc.) is gone.
>=20
> This new interface will be used by Libiio. The code is ready[1] and will
> be merged to the main branch as soon as the kernel bits are accepted
> upstream.
>=20
> Note that Libiio (and its server counterpart, iiod) use this new
> interface in two different ways:
> - by memory-mapping the DMABUFs to access the sample data directly,
> =C2=A0 which is much faster than using the existing fileio API as the sam=
ple
> =C2=A0 data does not need to be copied;
> - by passing the DMABUFs around directly to the USB stack, in a
> =C2=A0 device-to-device zero-copy fashion, using a new DMABUF interface f=
or
> =C2=A0 the USB (FunctionFS to be exact) stack, which is being upstreamed =
in
> =C2=A0 parallel of this patchset [2].
>=20
> As for write() support, Nuno (Cc'd) said he will work on upstreaming the
> DAC counterpart of adc/adi-axi-adc.c in the next few weeks, so there
> will be a user for the buffer write() support. I hope you are okay with
> this - otherwise, we can just wait until this work is done, and I still
> benefit from sending this patchset early to get feedback.
>=20

Indeed, I already started a discussion [1] since what we have now for=20
adc/adi-axi-adc.c has some major flaws (IMHO). So I'm hopping to get some
feedback/discussion to get "righter" from the beginning.


[1]: https://lore.kernel.org/linux-iio/dac3967805d7ddbd4653ead6d50e614844e0=
b70b.camel@gmail.com/T/#u

- Nuno S=C3=A1