dougg@xxxxxxxxxx wrote on Wed, 14 Mar 2007 12:18 -0400: > After reviewing this post by Pete Wyckoff: > http://marc.theaimsgroup.com/?l=linux-scsi&m=117278879816029&w=2 > > I decided to update my sg v4 interface document originally > posted 20061106 which I will now call release 1.1 : > http://lwn.net/Articles/208082/ > > Pete was proposing to put back din_iovec_count and > dout_iovec_count that had been dropped out of bsg but > had been in release 1.1 . Hmm. > > Some other items have been picked up from the bsg > implementation plus the suggestion from LSF'07 to > add dout_resid. > > See the attachment, comments welcome. Do you want to define the iovec format too? As I commented in my patch, v3 sg_iovec has pointers with 32/64-bit issues. Would be nice to see you declare v4 sg_iovec as pure u64. (By the way, don't use the patch: casting from the new to the old can put junk in the top half of the 64-bit sg_iovec.iov_len). Another issue I wonder about is queue DMA alignment. In bsg, blk_rq_map_user will use a bounce buffer if the user-supplied start and end addresses are not aligned. sg will happily map user pages at any offset without checking, although I haven't checked if Mike's patches change this. ll_rw_blk.c says regarding blk_rq_map_user: We don't allow misaligned data like bio_map_user() does. If the user is using sg, they're expected to know the alignment constraints and respect them accordingly. Should this still be true for both iovec and non-iovec uses of sgv4? I modified bsg to use iovec and ignore alignment issues, just like sg, but left in the bounce buffer for non-iovec usage. Seems awkward. scsi_ioctl's sg_io has the same odd situation: non-iovec is bounced, iovec must be aligned by user. -- Pete - 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
