linux-kernel - Re: Is anyone maintaining (or even using) usbtmc?

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Date:	Thu, 6 Aug 2009 12:54:28 -0700
From:	Greg KH <greg@...ah.com>
To:	Andrew Lutomirski <luto@....edu>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	gregkh@...e.de
Subject: Re: Is anyone maintaining (or even using) usbtmc?

On Mon, Aug 03, 2009 at 05:49:09PM -0400, Andrew Lutomirski wrote:
> On Mon, Aug 3, 2009 at 5:20 PM, Greg KH<greg@...ah.com> wrote:
> > On Mon, Aug 03, 2009 at 05:14:56PM -0400, Andrew Lutomirski wrote:
> >> Hi all-
> >>
> >> I'm trying to use usbtmc on an Aglient N9310A (The only TMC device I
> >> have), and it sort of works, but it seems to be both extremely buggy
> >> and missing a good deal of rather important functionality.  Is there
> >> anyone maintaining it?
> >
> > Yes, me.
> >
> >> If the answer is yes, I can describe the bugs (logspam, spurious
> >> errors, delayed messages, inability to read status, etc.) in greater
> >> detail.
> >
> > Please do, but also please use the latest version, in 2.6.30.3, we fixed
> > some bad problems in it recently.
> 
> I am.
> 
> Almost anything I do triggers this:
> 
> usbtmc 3-1:1.0: Unable to read data, error -110
> 
> The easiest way is to write something that wasn't a query and then try
> to read.  Of course, the read should fail, but there's no reason it
> should spam the logs.

Ok, care to send a patch reducing the error level of the message?

> On occasion, sending garbage to the device will cause even a
> subsequent USBTMC_IOCTL_CLEAR to fail with ETIMEDOUT.  (Maybe I wanted
> USBTMC_IOCTL_ABORT_BULK_IN?  That seems wrong, though, since
> presumably the driver should manage pending Bulk-IN requests on its
> own.)

Possibly, although I don't know the protocol for what should happen when
sending garbage to devices, except that it is probably undefined :)

> On other occasions (usually triggered by sending a garbage command,
> but, when this happens, the problem persists across several messages),
> every response will be delayed.  That is, if I send a query, I get
> back the previous query's answer or ETIMEDOUT if the previous command
> wasn't a query.  This persists across closing and reopening the
> device.
> 
> Sometimes write() fails with ETIMEDOUT.  This failure happens with no
> perceivable delay and I have no idea why.

Device problems?

> An ioctl for GET_CAPABILITIES would be nice, but is not mandatory.

What's wrong with the sysfs file for this instead?

> Finally, I see no way to read the USB488 status byte or detect a
> status interrupt.

Hm, is this in the spec somewhere that I missed?  Patches are always
welcome.

thanks,

greg k-h
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