Re: [Libusb-devel] libusb silently ignores permission errors

On 9/24/07, Alan Stern <[email protected]> wrote:
> On Mon, 24 Sep 2007, Xiaofan Chen wrote:
>
> > I remember you have a patch in the linux-usb-devel list which helps in
> > this situation so that lsusb (reading the descriptors) will not
> > unsuspend the device.
>
> Your memory is wrong.  I wrote a patch which will enable libusb to scan
> the existing buses and devices without wakening them all up.  But
> libusb has to be changed to take advantage of this, and that change
> hasn't been written.  Note: This is libusb, not lsusb.
>
> > Will it fix this issue?
>
> No.  Even if libusb were changed, it wouldn't help lsusb -- lsusb still
> would have to wake up a device in order to read its descriptors.
>

I see. I have updated the firmware based on some of the bug fixes
we found for the Microchip firmware in the Microchip Forum.
http://forum.microchip.com/tm.aspx?m=275422

Now it gets much better in the stock Ubuntu 7.04 kernel. lsusb
can find the device most of the time and fsusb (libusb based
host application) works most of the time as well. But occassionally
it still fails. So I need to dig further fix the firmware bugs.
But it seems to me not that easy to correctly handle
suspend and resume. I will try.

By the way, how do you like the idea of getting a console
version of usbview to replace lsusb? I think it will address the
problem of the original poster of this thread. My problem
seems a bit different -- after all is a firmware bug. It
seems to me that USBView does not use libusb. Or something
uses sysfs.

Regards,
Xiaofan

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