On Wed, 24 Jun 2009 23:21:04 +0800
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 24 Jun 2009, Alek Du wrote:
>
> > David,
>
> > union ehci_shadow {
> > - struct ehci_qh *qh; /* Q_TYPE_QH */
> > + struct ehci_qh_hw *qh_hw; /* Q_TYPE_QH */
> > struct ehci_itd *itd; /* Q_TYPE_ITD */
> > struct ehci_sitd *sitd; /* Q_TYPE_SITD */
> > struct ehci_fstn *fstn; /* Q_TYPE_FSTN */
>
> > +/* get ehci_qh_hw from shadow */
> > +#define SH_HW(x) ((x)->qh_hw)
> > +/* get ehci_qh from ehci_shadow */
> > +#define SH_QH(x) (SH_HW(x) ? SH_HW(x)->sw : NULL)
>
> You really have two choices for the shadow pointers. You can keep the
> pointer to the hardware structure (as you did here), or you could store
> the pointer to the software structure instead.
>
> It seems likely that the patch would be simpler if you took the second
> choice. (You might even find that you never need to use the
> backpointer from ehci_qh_hw to ehci_qh!) Have you considered doing it
> this way?
No, Alan,
union ehci_shadow {
struct ehci_qh_hw *qh_hw; /* Q_TYPE_QH */
struct ehci_itd *itd; /* Q_TYPE_ITD */
struct ehci_sitd *sitd; /* Q_TYPE_SITD */
struct ehci_fstn *fstn; /* Q_TYPE_FSTN */
__hc32 *hw_next; /* (all types) */
void *ptr;
};
the *hw_next requires all hardware structure here. There a lot codes that compare this with hw_next in HCD.
The hw_next is the first item for the 4 kinds of descriptors.
Alek
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