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.
Alan Stern
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