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SubjectRe: 2.6.29-rc libata sff 32bit PIO regression
On Mon, 2 Feb 2009, Sergei Shtylyov wrote:
> Hugh Dickins wrote:
> > But this patch works as well for me as the patch I posted before
> > (though much more verbose: please simplify if you see a better way).
>
> How about the following?
>
> unsigned char *tail = buf + buflen - slop;
> unsigned char pad[4];
>
> if (rw == READ) {
> if (slop <= 2)
> ioread16_rep(data_addr, pad, 1);
> else
> ioread32_rep(data_addr, pad, 1);
> memcpy(tail, pad, slop);

Too many tabs on the memcpy.

> } else {
> memcpy(pad, tail, slop);
> memset(pad + slop, 0, 4 - slop);

And we could make that line even more complicated!
But I think unsigned char pad[4] = {0, 0, 0, 0} would be better.
Though Alan didn't have it initialized at all: I don't know if
that was oversight or superior knowledge. In Alan's case, one
should usually assume the latter.

> if (slop <= 2)
> iowrite16_rep(data_addr, pad, 1);
> else
> iowrite32_rep(data_addr, pad, 1);
> }

Well, I don't know. I felt really pleased with using ioread16_rep
and the char array in my original patch, where slop might be 1 or 2
or 3; but once it comes down to always one single PIO op, I felt
it too lazy to be using the _rep form.

I really don't care, whatever works and best satisfies Alan.

> > - return words << 2;
> > +
> > + return buflen + (buflen & 1);
> >
>
> return (buflen + 1) & ~1;
>
> Well, I guess I could just have posted my own patch... :-)

Yes, do go ahead, I'm not desperate to get my name in there!

Hugh


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