Re: [PATCH 1/3] mfd: Add support for FTDI FT232H devices

[Johan Hovold <johan@kernel.org>]

On Fri, Jul 07, 2017 at 11:53:29AM +0200, Anatolij Gustschin wrote:
> On Fri, 07 Jul 2017 09:48:48 +0200
> Bjørn Mork bjorn@mork.no wrote:
> 
> >[adding Johan on the CC list]
> >
> >Anatolij Gustschin <agust@denx.de> writes:
> >
> >> +static struct usb_device_id ftdi_mfd_table[] = {
> >> +	{ USB_DEVICE(0x0403, 0x6014) },
> >> +	{}
> >> +};
> >> +MODULE_DEVICE_TABLE(usb, ftdi_mfd_table);  
> >
> >This device ID is currently handled by the ftdi_sio driver, so I believe
> >you at least have to explain how you intend these two drivers to
> >cooperate...
> 
> these drivers cannot cooperate, the different ftdi function modes
> use same device pins as in UART mode. So, you either can use the
> device in UART interface mode or in some different mode. I do not
> load the ftdi_sio module or do unbind the USB device from the
> ftdio_sio driver and bind it to the mfd driver, e.g.:
> 
>   sh -c "echo -n "3-2:1.0" > /sys/bus/usb/drivers/ftdi_sio/unbind"
>   sh -c "echo -n "3-2:1.0" > /sys/bus/usb/drivers/ftdi-mfd/bind"

I'm afraid that's not good enough. If we're going to support a non-UART
mode through a separate driver, we need to have all drivers for these
devices be able to retrieve the current mode during probe and only bind
when the mode matches.

Johan