Changing to microseconds would cause a lot of
needless pain. We'd have to change the field
name too, else know that we missed some of
those "interval /= 1000" (or "/= 125") modifications.
Lots of new error conditions (1usec interval and
so on) would surely cause trouble too.
USB itself specifies two ways to specify intervals
in endpoint_descriptor->bInterval. The units differ
(frames vs microframes, where uframe==125us)
also the encoding (linear vs logarithmic). Plus
interrupt and isochronous are just a bit different.
My second option was to do that log-to-linear
conversion in usb_fill_int_urb(). urb->interval is
already specified as frames or, for highspeed,
microframes, so that doesn't need changing.
With that option, most drivers could ignore this
issue unless (like maybe five drivers) they use
different interrupt polling intervals than found in
the endpoint descriptors. (*)
- Dave
(*) Or work with ISO transfers, which is another
issue: those drivers all assume a period of
one frame, ignoring the descriptors.
----- Original Message -----
From: "Oliver Neukum" <[EMAIL PROTECTED]>
To: "David Brownell" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Sunday, April 21, 2002 12:59 AM
Subject: Re: [linux-usb-devel] PATCH 2.5.8 -- hub polling interval (andquestion!)
Am Sonntag, 21. April 2002 05:21 schrieb David Brownell:
> Tough trick when some intervals come in microframes,
> so they're less than a millisecond.
>
> How would someone encode a 125 microsecond polling
> interval in your preferred world, then?
Oh, I see the problem.
> My second option, FWIW, was to embed the conversion
> in usb_fill_int_urb(), which is already in usbcore. USB 1.1
> drivers already talk in terms of milliseconds, they wouldn't
> notice the change.
I don't think it's a good idea to have two ways to specify it.
Could we go to microseconds for everything and have
a conversion macro ?
Regards
Oliver
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