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List:       linux-usb-devel
Subject:    Re: [linux-usb-devel] Non-input HID - take 2
From:       David Brownell <david-b () pacbell ! net>
Date:       2001-04-30 17:55:43
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> I think one reason why HID events are done through the
> default control pipe is that HID is designed to be able to
> express such complex input and output arrangements that there
> could easily be more inputs or output than the endpoint number,
> which are limited to something like 63 if I recall correctly.

Well, 30 endpoints apart from the control pipe.

I suspect Greg's comment about hardware costs is also
near the mark ... I was just looking at how the EZ-USB
code works (FX2 does USB 2.0! :) and those devices
actually have silicon support for control operations.

Silicon is used whenever 8051 firmware isn't processing
the control requests (before "renumeration" on many
devices).  Devices that are even further cost-reduced
might even be able to avoid the microcontroller costs.

- Dave




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