highmem pages

[Jeff Garzik <jgarzik@pobox.com>]

Here is an interesting code snippet from ide-scsi, that could be useful 
in libata:

>                 count = min(pc->sg->length - pc->b_count, bcount);
>                 if (PageHighMem(pc->sg->page)) {
>                         unsigned long flags;
> 
>                         local_irq_save(flags);
>                         buf = kmap_atomic(pc->sg->page, KM_IRQ0) + pc->sg->offse
> t;
>                         drive->hwif->atapi_input_bytes(drive, buf + pc->b_count,
>  count);
>                         kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
>                         local_irq_restore(flags);
>                 } else {
>                         buf = page_address(pc->sg->page) + pc->sg->offset;
>                         drive->hwif->atapi_input_bytes(drive, buf + pc->b_count,
>  count);
>                }