On Thursday, August 26, 2010 08:40:47 am FUJITA Tomonori wrote: > On Fri, 20 Aug 2010 14:50:12 +0300 > Marin Mitov <mitov@xxxxxxxxxxx> wrote: > > > On Friday, August 20, 2010 11:35:06 am FUJITA Tomonori wrote: > > > On Fri, 20 Aug 2010 11:13:45 +0300 > > > Marin Mitov <mitov@xxxxxxxxxxx> wrote: > > > > > > > > > This tric is already used in drivers/staging/dt3155v4l.c > > > > > > dt3155_alloc_coherent()/dt3155_free_coherent() > > > > > > > > > > > > Here proposed for general use by popular demand from video4linux folks. > > > > > > Helps for videobuf-dma-contig framework. > > > > > > > > > > What you guys exactly want to do? If you just want to pre-allocate > > > > > coherent memory for latter usage, > > > > > > > > Yes, just to preallocate not coherent, but rather contiguous memory for latter usage. > > > > We use coherent memory because it turns out to be contiguous. > > > > > > Hmm, you don't care about coherency? You just need contiguous memory? > > > > Yes. We just need contiguous memory. Coherency is important as far as when dma > > transfer finishes user land is able to see the new data. Could be done by something like > > dma_{,un}map_single() > > Then, we should avoid using coherent memory as I exaplained before. In > addition, dma_alloc_coherent can't provide large enough contigous > memory for some drivers so this patch doesn't help much. Please, look at drivers/media/video/videobuf-dma-contig.c. Using coherent memory is inavoidable for now, there is no alternative for it for now. The two new functions, which I propose are just helpers for those of us who already use coherent memory (via videobuf-dma-contig API). May be adding these two functions to drivers/media/video/videobuf-dma-contig.c will be better solution? Thanks. Marin Mitov > > We need the proper API for contiguous memory. Seem that we could have > something: > > http://lkml.org/lkml/2010/8/20/167 > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html