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Alan Stern authored
This patch does what you suggested. The read/write routines from the updated subdrivers are changed so they don't bother to differentiate between transfers that do or do not use scatter-gather. The low-level usb_stor_access_xfer_buf routine will Do The Right Thing regardless, and there probably won't ever be more than a few non s-g calls. (What about filesystem I/O requests to access metadata?) It turns out that in addition to removing some comments and a few tests, this change allowed me to remove the buffer and use_sg arguments passed to the read/write routines as well. So the simplification ended up being a bit bigger than I expected. While writing this patch, I noticed spots in several drivers that still need to be changed -- they slipped past me before. These drivers handle things like READ-CAPACITY or REQUEST-SENSE by copying the data directly to srb->request_buffer, which is obviously wrong if s-g is being used. I'll send in changes next week that convert them to use the usb_stor_set_xfer_buf function. Like you said, it's going to be handy in more places than originally intended!
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