USB mass storage and ARM cache coherency

[Benjamin Herrenschmidt]

On Fri, 2010-02-19 at 21:53 +0100, Oliver Neukum wrote:
> Am Freitag, 19. Februar 2010 18:36:51 schrieb Catalin Marinas:
> > If a page is already mapped in user space, flush_dcache_page() on ARM
> > does the flushing rather than deferring it to update_mmu_cache(). The
> > PIO HCD drivers, however, don't call flush_dcache_page(). Is it possible
> > that the HCD could transfer data into a page cache page already mapped
> > in user space? My understanding is that the scenario above is possible.
> 
> Yes, video drivers do that. 

In which case it would be up to the video driver to call
flush_dcache_page() (though if it's v4l you are talking about, maybe it
might make sense to push it into the v4l layer itself).

Cheers,
Ben.