[PATCH 22/22] usb: document that URB transfer_buffer should be aligned

[Alan Stern]

On Thu, 30 Mar 2017, Oliver Neukum wrote:

> Am Donnerstag, den 30.03.2017, 11:55 -0400 schrieb Alan Stern:
> > 
> > I'm pretty sure that usb-storage does not do this, at least, not when 
> > operating in its normal Bulk-Only-Transport mode.  It never tries to 
> > read the results of an earlier transfer after carrying out a later 
> > transfer to any part of the same buffer.
> 
> The storage driver takes buffers as the block layer (or sg) provide
> them, does it not?

Yes.  But it does not read the data from an earlier transfer after 
carrying out a later transfer on the same buffer.

The only possible example would be if the sense buffer for a command 
occupied part of the same block as the data buffer.  But this can't 
happen, because the sense buffer is allocated separately by its own 
kzalloc_node() call in scsi_init_request().

Alan Stern