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

[Christian König]

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.
>