[ Adding linux-usb as other may be interested in this. ]

On Thu, Jul 05, 2018 at 01:57:29PM +0100, Antonio Santagiuliana wrote:
> Thank you for the information.
> What I don't understand is that if I use the CP2105 are its GPIOs usable by
> this driver ?

Yes, they should be. But if I remember correctly, the pins in question
are muxed with different functions, so you need to make sure that the
device is configured correctly (e.g. using some silabs tool).

> If so, which is the interface to the user space ? I can open the driver
> usbserial but from the Raspberry pi user space I don't understand where the
> GPIOs from this chip are mapped to or how I should map them by creating a
> node with mknod ?

You can access them from /sys/class/gpio or using the new gpiolib
chardev interface as any other gpios.

If the gpios are recognised and registered, they should also show up in
sysfs as a child device to the USB interface in question, for example
as:
        
        /sys/bus/usb/devices/1-1.1\:1.0/gpio/gpiochipN

Good luck,
Johan
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