On 01/22/15 11:39, Nicholas A. Bellinger wrote: > Well, according to DMA-API.txt it's classified as: > > DMA_BIDIRECTIONAL direction isn't known > > and is unrelated to any actual SCSI bidi commands containing both WRITE > and READ payload buffers. I think I figured out why several SCSI LLDs are comparing sc_data_direction with DMA_BIDIRECTIONAL. In code that has been removed eight years ago I found the following construct (see also https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=21b2f0c803adaf00fce1b606c50b49ae8b106773): if (inlen == 0) { data_direction = DMA_FROM_DEVICE; } else if (outlen == 0 ) { data_direction = DMA_TO_DEVICE; } else { /* * Can this ever happen? */ data_direction = DMA_BIDIRECTIONAL; } Here is some more removed code from the same timeframe (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=beb40487508290f5d6565598c60a3f44261beef2): struct scsi_request *scsi_allocate_request(struct scsi_device *sdev, gfp_t gfp_mask) { const int offset = ALIGN(sizeof(struct scsi_request), 4); const int size = offset + sizeof(struct request); struct scsi_request *sreq; sreq = kzalloc(size, gfp_mask); if (likely(sreq != NULL)) { sreq->sr_request = (struct request *)(((char *)sreq) + offset); sreq->sr_device = sdev; sreq->sr_host = sdev->host; sreq->sr_magic = SCSI_REQ_MAGIC; sreq->sr_data_direction = DMA_BIDIRECTIONAL; } return sreq; } Bart. -- 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
