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? Then, I prefer to invent the API to allocate contiguous memory. Coherent memory is precious on some arches. > > why dma_pool API (mm/dmapool.c) doesn't work? > > I do not know why dma_pool API doesn't work for frame grabber buffers. > May be they are too big ~400KB. I have tried dma_pool APIs without success > some time ago, so I had to find some other way to solve my problem leading to > the proposed dma_reserve_coherent_memory()/dma_free_reserved_memory(). I think that dma_pool API is for small coherent memory (smaller than PAGE_SIZE) so it might not work for you. However, the purpose of dma_pool API is exactly for what you want to do, creating a pool for coherent memory per device for drivers. I don't see any reason why we can't extend the dma_pool API for your case. And it looks better to me rather than inventing the new API. -- 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
