On Thu, 25 Jun 2009 02:51:17 +0800
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> Fair enough. Here's how this could be rewritten, assuming we make the
> qh member of ehci_shadow point to the software structure (this was
> composed in email, so it's not compile-tested or anything):
>
> static void periodic_unlink(struct ehci_hcd *ehci, unsigned frame, void *ptr)
> {
> union ehci_shadow *prev_p = &ehci->pshadow[frame];
> union ehci_shadow here = *prev_p;
> __hc32 *hw_p = &ehci->periodic[frame];
> __hc32 tag = Q_NEXT_TYPE(ehci, *hw_p);
>
> /* find predecessor of "ptr"; hw and shadow lists are in sync */
> while (here.ptr && here.ptr != ptr) {
> if (hc32_to_cpu(tag) == Q_TYPE_QH)
> hw_p = &HW(here->qh)->hw_next;
> else
> hw_p = here.hw_next;
> prev_p = periodic_next_shadow(ehci, prev_p, tag);
> here = *prev_p;
> tag = Q_NEXT_TYPE(ehci, *hw_p);
> }
>
> However, I would prefer to redo all this in terms of a special-purpose
> iterator (something I've been considering adding). The iterator code
> could be reused in several places within ehci-sched.c:
>
> struct periodic_iterator {
> union ehci_shadow *prev_p;
> __hc32 *hw_p;
> unsigned tag;
> }
>
> static union ehci_shadow periodic_iterator_init(struct ehci_hcd *ehci,
> unsigned frame, struct periodic_iterator *iter)
> {
> iter->prev_p = &ehci->pshadow[frame];
> iter->hw_p = &ehci->periodic[frame];
> iter->tag = hc32_to_cpu(ehci, *iter->hw_p);
> if (iter->tag & 1) /* End of the list */
> return (union ehci_shadow) NULL;
> iter->tag &= (3 << 1);
> return *iter->prev_p;
> }
>
> static union ehci_shadow periodic_iterator_next(struct ehci_hcd *ehci,
> struct periodic_iterator *iter)
> {
> union ehci_shadow here = *iter->prev_p;
>
> iter->hw_p = here->hw_next;
> switch (iter->tag) {
> case Q_TYPE_QH:
> iter->prev_p = &here->qh->qh_next;
> iter->hw_p = &HW(here->qh)->hw_next;
> break;
> case Q_TYPE_FSTN:
> iter->prev_p = &here->fstn->fstn_next;
> break;
> case Q_TYPE_ITD:
> iter->prev_p = &here->itd->itd_next;
> break;
> // case Q_TYPE_SITD:
> default:
> iter->prev_p = &here->sitd->sitd_next;
> break;
> }
>
> iter->tag = hc32_to_cpu(ehci, *iter->hw_p);
> if (iter->tag & 1) /* End of the list */
> return (union ehci_shadow) NULL;
> iter->tag &= (3 << 1);
> return *iter->prev_p;
> }
>
> static void periodic_unlink(struct ehci_hcd *ehci, unsigned frame, void *ptr)
> {
> struct periodic_iterator iter;
> union ehci_shadow here;
>
> /* find predecessor of "ptr"; hw and shadow lists are in sync */
> here = periodic_iterator_init(ehci, frame, &iter);
> while (here.ptr && here.ptr != ptr)
> here = periodic_iterator_next(ehci, &iter);
>
> /* Now use iter.hw_p and iter.prev_p... */
>
> Alan Stern
>
Alan,
Can we do this in another separate patch? I guess it is some big change too.
Alek
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