On Thu, 13 Mar 2008, FUJITA Tomonori wrote:
> > > + for_each_sg(*sgl, sg, nents, i) {
> >
> > Will there be a problem in subsequent calls if *sgl has been
> > incremented but nents hasn't been changed? Maybe nents needs to be a
> > pointer also.
>
> usb_stor_access_xfer_buf doesn't check scsi_sg_count (the number of sg
> entries). It assumes that callers take care about the issue.
>
> If you want nents to be a pointer, I'm fine with it.
If nents doesn't change then for_each_sg() won't work right. There
could be an alternative macro:
/*
* Loop over each sg element, stopping at the end of the chain
*/
#define for_each_sg_all(sglist, sg, __i) \
for (__i = 0, sg = (sglist); sg; __i++, sg = sg_next(sg))
If you added this macro to include/linux/scatterlist.h and used it
instead of for_each_sg() then you can get rid of nents entirely.
However I'm not sure whether this would be safe. Do people sometimes
use a subset of the entries in a scatterlist?
If it isn't safe then nents would have to be passed as a pointer too.
At this stage I think it would be better to encapsulate sgl, offset,
and nents in a single structure than to pass multiple pointers.
Alan Stern
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