The IDE driver used DMA for ATAPI commands if READ/WRITE command is
multiple of sector size or sg command is multiple of 16 bytes. For
libata, READ/WRITE sector alignment is guaranteed by the high level
driver (sr), so we only have to worry about the 16 byte alignment.
This patch makes ata_check_atapi_dma() always request PIO for all data
transfer commands which are not multiple of 16 bytes.
The following reports are related to this problem.
http://bugzilla.kernel.org/show_bug.cgi?id=8605 (confirmed)
http://thread.gmane.org/gmane.linux.kernel/476620 (confirmed)
https://bugzilla.novell.com/show_bug.cgi?id=229260 (probably)
Albert first pointed out the difference between IDE and libata. Kudos
to him.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
b9a4197e26