Messages in this thread | | | Date | Wed, 31 Oct 2007 08:20:06 -0400 | From | Jeff Garzik <> | Subject | Re: "Fix ATAPI transfer lengths" causes CD writing regression |
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Jens Axboe wrote: > On Wed, Oct 31 2007, Alan Cox wrote: >> On Tue, 30 Oct 2007 19:21:29 +0000 >> Daniel Drake <dsd@gentoo.org> wrote: >> >>> Alan Cox wrote: >>>> I would guess Brasero is issuing a command with the length of data >>>> wrongly set. In the old code that might well just produce errors of the >>>> "Umm wtf is this data left over for ?", with the new code the drive is >>>> likely to change state as it knows the transfer size and that will >>>> *correctly* cause an HSM error and what follows. >>>> >>>> Now the question is who gets the length wrong - Brasero or the ata >>>> translation code in libata >>> Brasero does exactly the same as my test app which I attached to my last >>> mail. Is my test app wrong? >> Would need to double check the SCSI specificatons to be sure but I think >> you are asking for less data than the drive wishes to provide. You >> aren't allowed to do that with ATA. > > ide-cd handles this by throwing the excess away, which I think is the > sane way to do this.
That's easy for the PIO case. But CD writing is normally DMA, which means you will get a DMA engine exception if the device wants to give you more data than the scatter/gather entries permit.
Jeff
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