lkml.org 
[lkml]   [2011]   [Apr]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC] ARM DMA mapping TODO, v1
    On Thu, Apr 28, 2011 at 03:02:16PM +0200, Arnd Bergmann wrote:
    > I think the misunderstanding is that you are saying we need the flag
    > in dma_map_ops because you prefer to keep the cache management outside
    > of the individual dma_map_ops implementations.
    >
    > What I guess Jörg is thinking of is to have the generic IOMMU version
    > of dma_map_ops call into the architecture specific code to manage the
    > caches on architectures that need it. That implementation would of
    > course not require the flag in dma_map_ops because the architecture
    > specific callback would use other ways (hardcoded for an architecture,
    > or looking at the individual device) to determine if this is ever needed.
    >
    > That is also what I had in mind earlier, but you argued against it
    > on the base that putting the logic into the common code would lead
    > to a higher risk of people accidentally breaking it when they only
    > care about coherent architectures.

    You still need this same cache handling code even when you don't have
    an iommu. I don't see the point in having a dma_ops level of indirection
    followed by a separate iommu_ops level of indirection - it seems to me to
    be a waste of code and CPU time, and I don't see why its even necessary
    when there's a much simpler way to deal with it (as I illustrated).
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-04-28 15:21    [W:2.774 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site