From mboxrd@z Thu Jan  1 00:00:00 1970
From: Johan Hovold <johan@kernel.org>
Subject: Re: [PATCH 1/3] mfd: Add support for FTDI FT232H devices
Date: Mon, 10 Jul 2017 14:34:27 +0200
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To: Anatolij Gustschin <agust@denx.de>
Cc: =?iso-8859-1?Q?Bj=F8rn?= Mork <bjorn@mork.no>, Lee Jones <lee.jones@linaro.org>, Linus Walleij <linus.walleij@linaro.org>, Alan Tull <atull@kernel.org>, Moritz Fischer <moritz.fischer@ettus.com>, linux-gpio@vger.kernel.org, linux-fpga@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold <johan@kernel.org>
List-Id: linux-gpio@vger.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