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 <[email protected]>
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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