linux-kernel - Re: [PATCH] USB: ftdi

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Date:	Mon, 7 Jul 2014 12:44:28 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Sascha Silbe <x-linux@...ra-silbe.de>,
	Johan Hovold <jhovold@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] USB: ftdi_sio: add GPIO support

On Fri, Jun 13, 2014 at 8:31 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Fri, Jun 13, 2014 at 09:25:07AM +0200, Linus Walleij wrote:

>> But I also want to bring the device model into question: normally
>> when a mother device spawns children across different subsystems
>> we model them as MFD devices (drivers/mfd) that instantiate
>> children for the different subsystems. So you could spawn a
>> serial and a GPIO device from a USB-based hub device there.
>>
>> I do not know if that is really apropriate in this case. It seems the
>> device is first and foremost FTDI.
>>
>> But it could still spawn a child platform device for the GPIO stuff
>> so that this can live as a separate driver under drivers/gpio/gpio-ftdi.c
>> or similar.
>>
>> You could then use something like:
>>
>> struct platform_device *gdev;
>
> Ick, no, it's a USB device, do not abuse the platform_device code any
> more than it currently is (note, I HATE the platform device code,
> someday I'll delete it entirely...  Well, I can dream...)

Haha yeah :-)

However is the MFD cell approach acceptable?

Now MFD cells are platform_devices mind you, but it's
in principle just how that got implemented, MFD cells could
be device-something else.

Yours,
Linus Walleij
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