On Thu, 27 Apr 2006, Alan Stern wrote:
> On Thu, 27 Apr 2006, Jamie Guinan wrote:
>
> > Hi,
> >
> > I'm trying to talk to a Canon PowerShot A520 via libptp, which uses
> > libusb. The "ptpcam" app works once, then fails after that until I
> > dis/re-connect the camera.
> >
> > open("/proc/bus/usb/001/002", O_RDWR) = 3
> > ioctl(3, USBDEVFS_CLAIMINTERFACE, 0xbe810c64) = 0
> > ioctl(3, UI_DEV_DESTROY or USBDEVFS_BULK, 0xbe8109d4) = 16
> > ioctl(3, UI_DEV_DESTROY or USBDEVFS_BULK, 0xbe8109c4) = -1 ETIMEDOUT
> > (Connection timed out)
> > write(2, "ERROR: Could not open session!\nT"..., 56ERROR: Could not
> > open session!
> > Try to reset the camera.
> > ) = 56
> > ioctl(3, USBDEVFS_RELEASEINTERFACE, 0xbe810c68) = 0
> >
> > I haven't figured out why it behaves like this, but I'm looking at
> > usbsnoop logs to try and figure out how what the problem is. And I
> > found this in the logs,
> >
> > <snippet>
> > [1796 ms] >>> URB 6 going down >>>
> > -- URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER:
> > PipeHandle = 85bcfe14 [endpoint 0x00000081]
> > TransferFlags = 00000002 (USBD_TRANSFER_DIRECTION_OUT,
> > USBD_SHORT_TRANSFER_OK)
> > TransferBufferLength = 00000040
> > TransferBuffer = 85d0da98
> > TransferBufferMDL = 00000000
> > 00000000: 00 00 00 00 00 10 00 00 00 f0 98 02 00 00 00 00
> > 00000010: e8 e6 67 85 b0 1a 5f 85 00 00 99 02 00 00 00 00
> > 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > 00000030: 00 00 00 00 00 00 00 00 d8 1a 5f 85 10 e7 67 85
> > UrbLink = 00000000
> > [1807 ms] UsbSnoop - MyInternalIOCTLCompletion(f799fdb0) :
> > fido=85c8e0d0, Irp=85cc5ab0, Context=862edfa8, IRQL=2
> > [1807 ms] <<< URB 6 coming back <<<
> > -- URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER:
> > PipeHandle = 85bcfe14 [endpoint 0x00000081]
> > TransferFlags = 00000003 (USBD_TRANSFER_DIRECTION_IN,
> > USBD_SHORT_TRANSFER_OK)
> > TransferBufferLength = 0000000c
> > TransferBuffer = 85d0da98
> > TransferBufferMDL = 85c8ad90
> > 00000000: 0c 00 00 00 03 00 01 20 00 00 00 00
> > UrbLink = 00000000
> > </snippet>
> >
> > What puzzles me is that TransferFlags is USBD_TRANSFER_DIRECTION_OUT
> > going down, and USBD_TRANSFER_DIRECTION_IN coming up. Is this valid?
>
> It's hard to say what is valid when you're talking about Windows. :-)
>
> Regardless, the endpoint number is 0x81, which means it is an IN endpoint.
> So the transfer was definitely IN to the computer from the device.
>
> > If so, what would be the corresponding libusb call, usb_bulk_write or
> > usb_bulk_read?
>
> The corresponding call is usb_bulk_read.
Understood, thanks.
Another thing I observed was that its using asynchronous transactions,
so I can't properly emulate it with libusb 0.1.x. Are there CVS
snapshots of 1.x? Sourceforge anonymous cvs is almost never
available.
Funny, I've read about plenty of other PowerShot cameras working with
libptp, gPhoto, etc. Maybe the firmware changed on this one.
-Jamie
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