When the original urb is submitted, are you supposed to
put 64 bytes in the urb, and then 36 bytes in the next urb
(you as in the driver writer), or is this supposed to happen
transparently inside the urb resubmission code?
Neither ...
ie do I submit an URB with 100 bytes of data, or do I
== Roland King
== Vojtech Pavlik
This is a little similar to the discussion we were having last
week about how to do interrupt transfers on the usbdevfs
interface. The answer seemed to end up being that you should
just do bulk transfers.
Seemed -- if you can arrange that nothing
Hmm.. What would happen if I try to send a URB with 0 data size ?
UTSL ... or experiment!
Frankly it seems to me like a poor idea to be sending periodic
empty interrupt transfers, but I'm sure someone will say they
would like to use that as a device keepalive function!
- Dave
It seems to me that the distinction between interrupt transfers and bulk
transfers is somewhat artificial.
If you ignore bandwidth and other resource allocation issues, yes.
But those are very real issues in many systems.
On the wire you don't see much difference, except that there are
parts
; Simon Gittins; [EMAIL PROTECTED]
Subject: Re: [linux-usb-devel] stopping interrupt transfers..
On Tue, Feb 19, 2002 at 02:59:28AM -0800, David Brownell wrote:
By the host controller driver. It's a periodic transfer,
which _by design_ is going to be happening over and
over and over again
On Tue, 19 Feb 2002, Vojtech Pavlik wrote:
On Tue, Feb 19, 2002 at 02:59:28AM -0800, David Brownell wrote:
By the host controller driver. It's a periodic transfer,
which _by design_ is going to be happening over and
over and over again.
Which is a problem. All uses of interrupt out
= Vladimir Dergachev
= Vojtech Pavlik
= David Brownell
By the host controller driver. It's a periodic transfer,
which _by design_ is going to be happening over and
over and over again.
Which is a problem. All uses of interrupt out I have met don't need to
be
This is starting to make more sense now. I've been playing with the LEGO driver and
that's why I started asking these types of questions several days ago.
When the original urb is submitted, are you supposed to put 64 bytes in the urb, and
then 36 bytes in the next urb (you as in the driver
I'm puzzled about this thread. As I understand the discussion, seems that
someone is using an interrupt out for a small amount of data and, for some
unknown reason, the last data packet is being resent on each interrupt
interval. ...
There are some known reasons this failure mode might
And why there's that issue I mentioned (reported in Janary by
Wolfgang Mes) about changing the _length_ of an OUT transfer.
I've some comments I hope to send out, but can't do so much before
Wednesday.
It would work if most of the time the interrupt OUT URB could have a
transfer_length
Hello David!
So, the INTR-OUT problem. For example, maxpacket size is 64,
period is maybe 8, but the driver needs to send 100 bytes. That
adds up to 64 bytes in one frame, then 36 bytes after a delay of
8 frames ... then wanting to stop/unlink. This is one problem that
the LEGO folk
On Tue, Feb 19, 2002 at 11:30:02AM -0800, David Brownell wrote:
And why there's that issue I mentioned (reported in Janary by
Wolfgang Mes) about changing the _length_ of an OUT transfer.
I've some comments I hope to send out, but can't do so much before
Wednesday.
It would work
Right now the only portable solution is rather awkward.
That is:
(a) make sure urb-interval is long enough that it's
probably not going to suffer interrupt/scheduling
latency problems (causing extra transfers), and
submit the URB
(b) have your completion handler signal the thread
Hmm.. What would happen if I try to send a URB with 0 data size ?
thanks
Vladimir Dergachev
On Mon, 18 Feb 2002, David Brownell wrote:
Right now the only portable solution is rather awkward.
That is:
(a) make sure urb-interval is
To: Vladimir Dergachev; [EMAIL PROTECTED]
Subject: Re: [linux-usb-devel] stopping interrupt transfers..
Right now the only portable solution is rather awkward.
That is:
(a) make sure urb-interval is long enough that it's
probably not going to suffer interrupt/scheduling
latency
-Original Message-
From: David Brownell [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, 19 February 2002 7:16 AM
To: Vladimir Dergachev; [EMAIL PROTECTED]
Subject: Re: [linux-usb-devel] stopping interrupt transfers..
Right now the only portable solution is rather awkward
On Mon, Feb 18, 2002 at 06:58:28PM -0500, Roland King wrote:
This is a little similar to the discussion we were having last
week about how to do interrupt transfers on the usbdevfs
interface. The answer seemed to end up being that you should
just do bulk transfers.
I have read the USB
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