Posted by John Navas on 01/22/08 01:30

On Tue, 22 Jan 2008 00:29:14 +0000 (UTC), Ilya Zakharevich
<nospam-abuse@ilyaz.org> wrote in <fn3dcq$7bi$1@agate.berkeley.edu>:

>[A complimentary Cc of this posting was sent to
>Dave Martindale
><davem@cs.ubc.ca>], who wrote in article <fn2g30$q72$1@swain.cs.ubc.ca>:
>> >Do not see any significant difference. The poller would set up a
>> >wake-up call, which would generate an interrupt. [And, BTW, why my
>> >PCI hardware view shows that USB controllers use interrupts?]
>>
>> More likely, the poller would set a wakeup call, which would add an
>> entry into a timer queue somewhere. The timer interrupts regularly,
>> and when the specified time has elapsed, the process that asked for the
>> wakeup is scheduled to run again. But it would need to wait for CPU
>> resources to do anything. It's unlikely to be called directly from the
>> timer interrupt handler.
>
>AFAIK, with any sane OS, a device driver requiring wakeup would not
>wait for scheduler. (The scheduler usually has too coarse granularity
>- 1msec or above.)

You're assuming a smart bus. USB is simple and cheap.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

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