Alan Cox wrote:
Correct, but it is also extremely slow. No point discussing fast paths for odd if() tests through the code when you burn 100nS unneccessarily every time you issue a command via PIO is there.
BTW if you wanna start PIO speed tuning, ISTR the device-select code does not cache selections. We always unconditionally select a device before a command in ata_qc_issue_prot(), IIRC.
ISTR for some cases this was intentional (following ATADRVR) but I bet adding code to -not- select a device, if it is already selected, would speed things up on slow PATA machines.
ata_qc_issue_prot() and ata_dev_select() would be starting points if you're interested.
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