linux-kernel - Re: [PATCH 3/9] dma-heap: Provide accessors so that in-kernel drivers can allocate dmabufs from specific heaps

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <95797f3d-65bf-1bd9-9e19-6de42605cfe3@gmail.com>
Date:   Tue, 12 Sep 2023 16:46:30 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Yong Wu (吴勇) <Yong.Wu@...iatek.com>,
        "jstultz@...gle.com" <jstultz@...gle.com>
Cc:     "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jianjiao Zeng (曾健姣) 
        <Jianjiao.Zeng@...iatek.com>,
        Kuohong Wang (王國鴻) 
        <kuohong.wang@...iatek.com>,
        "Brian.Starkey@....com" <Brian.Starkey@....com>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
        "tjmercier@...gle.com" <tjmercier@...gle.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 3/9] dma-heap: Provide accessors so that in-kernel drivers
 can allocate dmabufs from specific heaps

Am 12.09.23 um 10:52 schrieb Yong Wu (吴勇):
> [SNIP]
>> But what we should try to avoid is that newly merged drivers provide
>> both a driver specific UAPI and DMA-heaps. The justification that
>> this
>> makes it easier to transit userspace to the new UAPI doesn't really
>> count.
>>
>> That would be adding UAPI already with a plan to deprecate it and
>> that
>> is most likely not helpful considering that UAPI must be supported
>> forever as soon as it is upstream.
> Sorry, I didn't understand this. I think we have not change the UAPI.
> Which code are you referring to?

Well, what do you need this for if not a new UAPI?

My assumption here is that you need to export the DMA-heap allocation 
function so that you can server an UAPI in your new driver. Or what else 
is that good for?

As far as I understand you try to upstream your new vcodec driver. So 
while this change here seems to be a good idea to clean up existing 
drivers it doesn't look like a good idea for a newly created driver.

Regards,
Christian.

>>> So I think this patch is a little confusing in this series, as I
>> don't
>>> see much of it actually being used here (though forgive me if I'm
>>> missing it).
>>>
>>> Instead, It seems it get used in a separate patch series here:
>>>     
>> https://lore.kernel.org/all/20230911125936.10648-1-yunfei.dong@mediatek.com/
>>
>> Please try to avoid stuff like that it is really confusing and eats
>> reviewers time.
> My fault, I thought dma-buf and media belonged to the different tree,
> so I send them separately. The cover letter just said "The consumers of
> the new heap and new interface are our codecs and DRM, which will be
> sent upstream soon", and there was no vcodec link at that time.
>
> In the next version, we will put the first three patches into the
> vcodec patchset.
>
> Thanks.
>