On Thu, 2006-11-23 at 15:03 +0000, Ralf Baechle wrote: > dma_is_consistent() is ill-designed in that it does not have a struct device > argument which makes proper support for systems that consist of a mix of > coherent and non-coherent DMA devices hard. At the time the interface was designed, the general consensus was that it was easier to recognise incoherent memory regions by their address range than by which device they came from. The main proponent of this being arm, if I remember rightly. > There also is just a single > user, a BUG_ON() call in the 53c700.c SCSI driver so removing instead of > fixing it up seems to be the thing to do. Really, no, this is a bad idea. However, if you want to make it per device as well as per dma_addr_t, please feel free ... the patch will be marginally smaller than the one you just submitted ... > - /* all of these offsets are L1_CACHE_BYTES separated. It is fatal > - * if this isn't sufficient separation to avoid dma flushing issues */ > - BUG_ON(!dma_is_consistent(pScript) && L1_CACHE_BYTES < dma_get_cache_alignment()); Really, this is a good BUG_ON; it detects a condition that would cause incredibly subtle and extremely hard to diagnose data corruption problems in the driver caused by mixed cacheline incoherency. It's the price I paid in the driver for having my data separations for the mailboxes determined at compile time rather than runtime. If you want to take this out, we need to use dma_get_cache_alignment() to determine the mailbox separations and set them up accordingly at runtime. James - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
