On Wed, Jan 14, 2009 at 8:32 AM, Vineet Gupta <vineetg76@xxxxxxxxx> wrote: > Hi, > > I've read dma mapping and dma-api kernel documentation as well as the > DMA API change at http://lwn.net/Articles/75780/ which describes fork > of dma_sync_* to dma_sync_*_for_cpu and dma_sync_*_for_device. > > It seems the names of API are self explanatory and direction parameter > is not needed (except for handling BIDIRECTIONAL case). > So for e.g. If software wants to access the dma buffer, post DMA, it > will invoke dma_sync_single_for_cpu so that non-coherent arch can > invalidate the corresponding cache lines. This implies FROM_DEVICE > semantics. Does that mean dma_sync_single_for_cpu invoked with > direction = TO_DEVICE should return error. drivers/ieee1394/sbp2.c: static int sbp2_create_command_orb(struct sbp2_lu *lu, struct sbp2_command_info *cmd, struct scsi_cmnd *SCpnt) { dma_sync_single_for_cpu(dmadev, cmd->command_orb_dma, sizeof(struct sbp2_command_orb), DMA_TO_DEVICE); ??? > Corollary case is when dma_sync_single_for_device is invoked with > direction = FROM_DEVICE, is tha error too (buggy driver). > > The architecture for which I'm implementing DMA coherency APIs has > non-coherent DMA memory and logical-to-bus mapping / DMA bounce is not > a issue. > > Thanks, > Vineet > -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
