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Date:   Tue, 12 Sep 2023 16:46:30 +0200
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Subject: Re: [PATCH 3/9] dma-heap: Provide accessors so that in-kernel drivers
 can allocate dmabufs from specific heaps
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From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>
In-Reply-To: <255ae6b9ac1b6bea9262069747824b8461475e70.camel@mediatek.com>
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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.
>