linux-kernel - Re: [PATCH v8] usb:serial:pl2303: add GPIOs interface on PL2303

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Date:	Fri, 5 Sep 2014 09:58:38 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	zoobab@...il.com
Cc:	Wang YanQing <udknight@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Johan Hovold <jhovold@...il.com>, andi@...as.de,
	dforsi@...il.com, One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8] usb:serial:pl2303: add GPIOs interface on PL2303

On Thu, Sep 4, 2014 at 11:57 PM, Benjamin Henrion <zoobab@...il.com> wrote:
> On Thu, Sep 4, 2014 at 7:35 PM, Wang YanQing <udknight@...il.com> wrote:
>> On Sun, Aug 31, 2014 at 11:24:56PM +0800, Wang YanQing wrote:
>>> PL2303 USB Serial devices may has GPIOs, this patch add
>>> basic PL2303 gpio support.
>>>
>>> Known issue:
>>> If gpios are in use(export to userspace through sysfs interface, etc),
>>> then call pl2303_release(unplug usb-serial convertor, modprobe -r, etc),
>>> will cause trouble, so we need to make sure there is no gpio user before
>>> call pl2303_release.
>>>
>>> Signed-off-by: Wang YanQing <udknight@...il.com>
>>> ---
>>>  Note: I sniffed office HXD gpio test program to get
>>>        gpios control protocol with PL2303 RA, so I only
>>>        test it with PL2303 RA and HXA, I don't have HXD,
>>>        but because it is *office* HXD gpio test program,
>>>        so if it doesn't work with HXD, I will feel surprise.
>
> I can confirm your patch is working fine on the HXD:
>
> http://www.zoobab.com/pl2303hxd-gpio
>
> I am still hunting for a simple C program to test the speed of the
> GPIOs and sysfs, if you have a good reference.

The exercise of the GPIO sysfs interface should be discouraged.
I would put emphasis on in-kernel tests and working on a better
userspace GPIO interface than the sysfs thing.

Yours,
Linus Walleij
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