libgphoto2 / libusb access to cameras works only once

[msmeissn]

Hi,

I am receiving bugreports from various sources, that libgphoto2 / libusb based access to remote control cameras
only works once.

After the first (working) access, the USB device no longer responds to writes, it is unclear if is stalled somehow or
some other USB problem exists.

This is be specific to the Raspberry PI.

Usually only USB bulktransfers are done, but USB interrupts transfers might also have played a role.

[DAFlippers]

Are you using Libusb_interrupt_transfer to read the frames?

David

[msmeissn]

Not sure if libusb 0.x or libusb 1.x is in use, but basically yes.

(libusb 1.x code is like:
ret = libusb_interrupt_transfer (port->pl->dh, port->settings.usb.intep,
(unsigned char*)bytes, size, &curread, timeout);
)

[DAFlippers]

I have reported LIBUSB-1.0 interrupt _transfer issue already:
#79 (comment)

The calls do not return data although data is read(/written) from(/to) the USB.

David

[ghollingworth]

Was this effected by the recent changes to reduce NAK overheads? I saw a marked performance increase in interrupt transfers with this change.

[drott]

@ghollingworth - since I tried this with the latest kernel in #218 the response to your question would be no, no change.

[drott]

@msmeissn The issue happens in both cases, no matter whether gphoto2 is linked with libusb 0.1 or 1.0.11.

[ghollingworth]

Many changes in USB recently, retry, reopen if still broken

[drott]

@ghollingworth alright - saw the committs in dwc_otg, will try again soon, thanks.

[ghollingworth]

Seems the issue is still occurring with latest changes to USB, any idea how to reproduce the problem? Can it be done with a Canon D50?

[drott]

I would assume it's rather independent of the camera model. #218 has the reproduction steps.
When running
$ strace gphoto2 --summary
twice, the second time the trace shows gphoto2 running into a loop retrying the USBDEVFS_REAPURBNDELAY ioctl.

Same happens basically when you try any larger gphoto usb operation, for example --list-files.