Messages in this thread | | | Date | Mon, 17 Sep 2007 06:00:19 -0400 | From | Jeff Garzik <> | Subject | Re: [PATCH 1/1] pata_it821x: fix lost interrupt with atapi devices |
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Tejun Heo wrote: > [cc'ing Albert and linux-ide] > > Alan Cox wrote: >> /from the media. */ >>> > + if (qc->nbytes < 2048) >>> > + return -EOPNOTSUPP; >>> > + >>> > /* No ATAPI DMA in smart mode */ >>> > if (itdev->smart) >>> > return -EOPNOTSUPP; >>> > >>> >>> This looks like a gross hack. Aren't you supposed to inspect >>> the command instead and whitelist the ones you know are OK, >>> like pata_pdc2027x.c and sata_promise.c do? >> It does seem to be about transfer size in the IT821x case not commands. >> It may be to do with how we issue ATAPI command transfer sizes from high >> up (patch went to Jeff) but for now this is definitely the right approach >> >> Reviewed-by: Alan Cox <alan@redhat.com> > > I wonder whether we should be using similar check in generic path too. > We have quite a few cases where MWDMA ATAPI devices choking on commands > with small transfer sizes. I don't think we'll experience significant > performance regression with this applied and even if there is some, it's > far better to have slightly slower working device. > > What do you guys think?
Need to look at, or know, a standard profile of submitted commands. It's quite possible some high performance commands want this, where possible.
Jeff
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