Alan Cox wrote: > On Thu, 29 Nov 2007 23:33:28 +0900 > Tejun Heo <[EMAIL PROTECTED]> wrote: > >> Depending on how many bytes are transferred as a unit, PIO data >> tranasfer may consume more bytes than requested. Knowing how much >> data is consumed is necessary to determine how much is left for >> draining. This patch update ->data_xfer such that it returns the >> number of consumed bytes. > > Why do we care ? > > If the drive and controller disagree or the drive has gone off its > trolley all we actually care about is when the thing stops saying there > is data. In addition all our methods transfer the entire block they are > asked to each time.
It's for draining. Let's say drive says it wanna transfer 18 bytes but the buffer is only 13 bytes long. If the transfer method consumes 2 bytes per read, it would consume 14 bytes. If the transfer method consumes 4 bytes per read, it would consume 16 bytes. If we drain too much, we risk hanging the machine. -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
