Besides my other reply, I have a couple comments:
On Wed, 16 May 2001, Georg Acher wrote:
>On Tue, May 15, 2001 at 02:00:04PM -0400, Dan Streetman wrote:
>> Note that usb-ohci.c was not treating 0-interval interrupts as one-shot; I
>> changed it to treat 0-interval interrupts as 1-shot. However the documentation
>> (URB.txt) doesn't mention 0-interval/one-shot interrupts at all! So either the
>> uhci HCDs or the documentation is wrong...?
>
>As far as I can recall, these one-shot interrupts were a speciality of uhci
>and not mentioned in our original URB "spec". I preferred a bulk replacement
>at that time, but since a driver author (I can't remember who) wanted them,
>I added this behavior afterwards.
Yes, one-shot 0-interval interrupt URBs are functionally equivalent to bulk
URBs. However, one-shot non-0-interval URBs are *not* equivalent. Bulk polling
is as fast as possible, which at least some low-speed interrupt devices can't
handle (I have one such device).
>> -Allow all URB types to be resubmitted (have a urb->resubmit flag).
>
>That's exactly the case I don't understand and why the patches for *uhci are
>actually needed. Why do you need a resubmit for interrupts? Interrupt URBs
>run as long as you don't kill them. Actually resubmission seems pretty
>useless to me.
Well, I don't agree that resubmission is useless. Anyway the patch I
submitted was *disabling* resubmission for interrupt URBs (with a flag), not
enabling it. Just making sure that's clear.
>> -Allow all URB types to be queued! (I think OHCI already does this?)
>
>This is a hardware issue. OHCI can do this in hardware, UHCI needs much help
>with a complicated descriptor structure and pointer handling.
>For *uhci, only control transfers currently lack the the queue ability,
>isochrounous did it since beginning and for queued interrupts I simply see no
>use (a sort of semantic nonsense...).
I disagree, queued non-resubmitting interrupt URBs would be very useful when
used by usbdevfs (i.e., userspace programs).
--
Dan Streetman
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