# Re: \[PATCH 05/28\] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT

- From: Christoph Hellwig \<hch@lst.de\>
- Date: 2020-08-19 13:57:49 
- List: netdev
- Page: https://ratatoskr.run/netdev/2020/08/6074148
- Thread: https://ratatoskr.run/alsa-devel/2020/08/6073543/t.md

```text
On Wed, Aug 19, 2020 at 02:49:01PM +0200, Tomasz Figa wrote:
> With the default config it doesn't, but with
> CONFIG_DMA_NONCOHERENT_CACHE_SYNC enabled it makes dma_pgprot() keep
> the pgprot value as is, without enforcing coherence attributes.

Which isn't selected on arm64, and that is for a good reason.

> AFAIK dma_cache_sync() isn't the only way to perform the cache
> synchronization.

Yes, it is the only documented way to do it.  And if you read the whole
series instead of screaming you'd see that it provides a proper way
to deal with non-coherent memory which will also work with arm64.
instead of screaming 

> By the way, as a videobuf2 reviewer, I'd appreciate being CC'd on any
> series related to the subsystem-facing DMA API changes, since
> videobuf2 is one of the biggest users of it.

The cc list is too long - I cc lists and key maintainers.  As a reviewer
should should watch your subsystems lists closely.
```