Low speed BULK endpoints on UHCI

G'day all,

Perhaps I'm flogging a dead horse, and I *know* this came up only recently but my desire to see this 
gross violation of the USB specs actually function is that "It works on the other two Operating 
Systems - Win and OSX".

In addition, prior to the patch recently submitted by Alan Stern which converts low speed bulk 
endpoints to interrupt, it used to work on any OHCI controller I had available.

The device in question is emulating a CDC-ACM device, and therefore used the usb-serial/generic 
driver. If I comment out Alan's addition to control.c and use my OHCI card it works.. If I want to 
use it on any of my desktop machines I need to comment out the check in uhci-q.c (which is a bit of 
an ugly workaround).

I did see an objection raised last time this came up by David Brownell regarding the bulk packet 
size starving the bus segment, but in my tests there appears to be zero difference between the bulk 
packet size and the interrupt packet size in any case. They are both a maximum of 8 bytes for 
low-speed and a minimum of whatever the device happens to send.

Monitoring this particular device, the average packet size to and from the device (bulk) is 1 or 2 
bytes + sync, PID and CRC, just the same as an interrupt packet.

I know the device violates the USB Specs (I developed it).. but then quite a few appear to also. I 
can't make it use full-speed as I'm doing the USB SIE in software and just don't have the cycles 
available to get it to go that fast.

The other option is to find some way of making the usb-serial/generic driver able to substitute 
interrupt for bulk endpoints where required (and I've spent a bit of time investigating that, but my 
knowledge of the linux usb stack is pretty shaky)

It's a bit of a bugger when developing something to assist people developing hardware/software and 
have to tell them they need to use Windows or MacOS as your firmware won't work with Linux.

I have my flame-proof undies on and am fully prepared to be shot down, I just wonder about the 
*practical* reasons why we must enforce this limitation when the others don't and nobody seems to 
complain? (Especially given half the hardware *OHCI* don't enforce it in any case)

Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

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