Detact the kernel driver to allow libusb to control the device.

[mithro]

On our Atlys board, we flash the Cypress with "fx2loader -v 1d50:602b HDMI2USB-firmware-prebuilt/hdmi2usb.hex ram" and then uvcvideo and cdc-acm drivers connect to the new endpoints.

This patch lets us use "flcli -v 1d50:602b:9994 -i fb9a:fb9a" to return the Cypress into programming mode.

[94023.794451] cdc_acm 2-1.1:1.2: ttyACM0: USB ACM device
[94026.571620] usb 2-1.1: USB disconnect, device number 19
[94028.051519] usb 2-1.1: new high-speed USB device number 20 using ehci-pci
[94028.144983] usb 2-1.1: New USB device found, idVendor=1d50, idProduct=602b
[94028.144995] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[94028.145002] usb 2-1.1: Product: FPGALink/FX2 20140311
[94028.145007] usb 2-1.1: Manufacturer: MakeStuff
[95015.404214] usb 2-1.1: USB disconnect, device number 20
[95017.138867] usb 2-1.1: new high-speed USB device number 21 using ehci-pci
[95017.231537] usb 2-1.1: config 1 interface 2 altsetting 0 endpoint 0x81 has an invalid bInterval 17, changing to 8
[95017.232517] usb 2-1.1: New USB device found, idVendor=fb9a, idProduct=fb9a
[95017.232527] usb 2-1.1: New USB device strings: Mfr=2, Product=1, SerialNumber=1
[95017.232533] usb 2-1.1: Product: HDMI2USB
[95017.232538] usb 2-1.1: Manufacturer: JANI
[95017.232542] usb 2-1.1: SerialNumber: HDMI2USB
[95017.233332] uvcvideo: Found UVC 1.00 device HDMI2USB (fb9a:fb9a)
[95017.233558] uvcvideo: UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround.
[95017.234742] cdc_acm 2-1.1:1.2: This device cannot do calls on its own. It is not a modem.
[95017.234852] cdc_acm 2-1.1:1.2: ttyACM0: USB ACM device
[95023.085273] usb 2-1.1: USB disconnect, device number 21
[95024.564253] usb 2-1.1: new high-speed USB device number 22 using ehci-pci
[95024.657215] usb 2-1.1: New USB device found, idVendor=1d50, idProduct=602b
[95024.657228] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[95024.657234] usb 2-1.1: Product: FPGALink/FX2 20140311
[95024.657239] usb 2-1.1: Manufacturer: MakeStuff

[makestuff]

This looks good in principle. A couple of minor problems though:

1. You're using a local "int i" in a for loop, which will break the Microsoft compiler. There's already a suitable "i" variable that's used earlier, so you can just re-use that.
2. Typo alert: does "detact" mean "detect" or "detach"?
3. Formatting - I use spaces either side of the parens in "for", "while", "if", etc, so "if ( libusb_kernel_driver_active(retVal, i) )".
4. Error handling - if something goes wrong in the code following the call to libusb_open(), the value of "retVal" is overwritten (by the CHECK_STATUS() macro), causing a resource leak. You probably want to use a different variable rather than retVal, and have an error label at the end that will call libusb_close() on it if an error is detected in the detach code. Have a look at the error handling for usbOpenDevice(), for example.