linux-kernel - Re: dynamic DMA-buf sharing between devices

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Message-ID: <7cc155fc-1582-9a80-283a-f9e7c84b120d@gmail.com>
Date:   Thu, 18 Apr 2019 12:57:44 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     sumit.semwal@...aro.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org
Subject: Re: dynamic DMA-buf sharing between devices

Am 18.04.19 um 11:13 schrieb Daniel Vetter:
> On Tue, Apr 16, 2019 at 08:38:29PM +0200, Christian König wrote:
>> Hi everybody,
>>
>> core idea in this patch set is that DMA-buf importers can now provide an optional invalidate callback. Using this callback and the reservation object exporters can now avoid pinning DMA-buf memory for a long time while sharing it between devices.
>>
>> I've already send out an older version roughly a year ago, but didn't had time to further look into cleaning this up.
>>
>> The last time a major problem was that we would had to fix up all drivers implementing DMA-buf at once.
>>
>> Now I avoid this by allowing mappings to be cached in the DMA-buf attachment and so driver can optionally move over to the new interface one by one.
>>
>> This is also a prerequisite to my patchset enabling sharing of device memory with DMA-buf.
> Ok, with the discussions and thinking I think this design is solid and
> should work out. Bunch of api and documentation polishing still to do, to
> make sure we have really clear semantics and as little room as possible
> for misunderstanding - refactoring a mess in dma-buf is a lot more tricky
> than just ttm, there's a lot more users.

Yeah, I'm pretty aware of that after changing all the users of the map 
API to use a structure for the parameters.

Well at least it's not UAPI :)

Christian

> -Daniel