Hi Ryan,
On Friday, 16. November 2012 11:10:00 Ryan C. Underwood wrote:
> This patch fixes misleading errors being sent to the application from
> libftdi.
>
> Background: usb_open() will silently succeed when the device node can
> only be opened read-only and not read-write. When this occurs,
> various subsequent ioctls to that node will fail, and are presented to
> the application as failures of those specific operations, even though
> the root cause is a permissions error.
>
> Using usb_claim_interface after every usb_open() would reveal a
> permissions problem earlier, but it is desirable in this case to scan
> properties of USB devices to find FTDI chips without necessarily
> attempting to claim every device for exclusive access.
>
> The patch ensures that when libftdi performs a libusb operation on an
> opened but not claimed USB device, a failure due to a permissions
> error will be propagated to the application as a permissions error and
> not a different, red-herring error.
Nice patch!
One question: What about using a new, separate error code
for the "permission denied" situation? Like -12.
Cheers,
Thomas
--
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