On 02/06/2005 14:26, David Brownell wrote:
On Thursday 02 June 2005 4:45 am, Ian Abbott wrote:
The ftdi_sio driver does bulk URB queueing and runs into similar
problems with the uhci driver, but I found it worked okay using the
usb-uhci driver instead. Well, this was a couple of years ago:
<http://marc.theaimsgroup.com/?l=linux-usb-devel&m=104644754217627&w=2>
Well, the same driver should work over _all_ HCDs with no changes
or HCD-specific code. The end-user shouldn't care, or need to
switch HCDs depending on what driver they want to use today ...
plus, I recall also finding differences in fault reporting and
recovery that would also affect drivers.
The URB queueing stuff in ftdi_sio was implemented some time before the
the problems with the uhci driver were known. I guessed I lived in hope
that it would get fixed one day. (I even tried debugging it with
printk's, but got horribly lost. I wouldn't like to maintain those
drivers!)
It's stuff like that that made me just conclude it wasn't worth
the effort of using queueing on 2.4 kernels. YMMV but that's
why I advise avoiding it.
I may get around to ripping that stuff out of ftdi_sio someday and
replacing it with something else. Maybe a single write URB and two
transfer buffers. The driver could be filling one transfer buffer while
waiting for the other to come back with the URB in the write bulk
callback. It should also make the write_room function more accurate -
it can just return the space left in the "currently being filled" buffer.
--
-=( Ian Abbott @ MEV Ltd. E-mail: <[EMAIL PROTECTED]> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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