On Thu, Aug 20, 2020 at 06:43:47AM +0200, Christoph Hellwig wrote: > On Wed, Aug 19, 2020 at 03:57:53PM +0200, Tomasz Figa wrote: > > > > Could you explain what makes you think it's unused? It's a feature of > > > > the UAPI generally supported by the videobuf2 framework and relied on > > > > by Chromium OS to get any kind of reasonable performance when > > > > accessing V4L2 buffers in the userspace. > > > > > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > > > so by definition it isn't used by any of these media drivers. > > > > It's still an UAPI feature, so we can't simply remove the flag, it > > must stay there as a no-op, until the problem is resolved. > > Ok, I'll switch to just ignoring it for the next version. So I took a deeper look. I don't really think it qualifies as a UAPI in our traditional sense. For one it only appeared in 5.9-rc1, so we can trivially expedite the patch into 5.9-rc and not actually make it show up in any released kernel version. And even as of the current Linus' tree the only user is a test driver. So I really think the best way to go ahead is to just revert it ASAP as the design wasn't thought out at all.
