On Mon, 2007-11-19 at 09:09 -0600, James Bottomley wrote: > > What other drivers do is DMA to their own allocation and then memcpy to > > the sense buffer. > > > > There is a movement to allocate the sense data as its own sg list, but > > I don't think that patch has even been posted yet. > > I'd like to be rid of it inside the command for various reasons: every > command has one of these, and they're expensive in the allocation (at 96 > bytes). There's no reason we have to allocate and free that amount of > space with every command. In theory, the number of these is bounded at > the queue depth, in practice, there's usually only one, and this DMA > alignment issue does requires most drivers to double copy. And most drivers don't and break. Take USB storage, I -think- (code path aren't trivial to follow) it just gets the sglist cooked up by the code in scsi_error.c no ? That just points to the buffer in scsi_cmnd. It then pass that for DMA to the USB stack. Ben. - 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
