linux-kernel - Re: [PATCH v3 3/3] gpio: add support for the Diolan DLN-2 USB GPIO driver

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Date:	Tue, 9 Sep 2014 13:27:01 +0300
From:	Octavian Purdila <octavian.purdila@...el.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexandre Courbot <gnurou@...il.com>, wsa@...-dreams.de,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Laurentiu Palcu <laurentiu.palcu@...el.com>,
	linux-usb@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
	linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v3 3/3] gpio: add support for the Diolan DLN-2 USB GPIO driver

On Tue, Sep 9, 2014 at 12:36 PM, Johan Hovold <johan@...nel.org> wrote:
> On Fri, Sep 05, 2014 at 07:04:51PM +0300, Octavian Purdila wrote:
>> On Fri, Sep 5, 2014 at 6:38 PM, Johan Hovold <johan@...nel.org> wrote:
>> > On Fri, Sep 05, 2014 at 06:17:59PM +0300, Octavian Purdila wrote:
>
>> > In general, how well have these patches been tested with disconnect
>> > events? At least gpiolib is known to blow up (sooner or later) when a
>> > gpiochip is removed when having requested gpios.
>>
>> I do disconnect tests regularly. Since switching to the new irq
>> interface the following patch is needed:
>>
>> https://lkml.org/lkml/2014/9/5/408
>>
>> With it and the current patch sets things seems to work well.
>
> I see no comments from Linus W on that patch?
>
> And I can confirm that things do blow up.
>
> After disconnecting while having a gpio exported, I get the familiar
> OOPS below when reconnecting the device.
>
> This has also been reported here:
>
>         https://lkml.org/lkml/2014/8/4/303
>

Hi Johan,

I did not test with gpio exported via sysfs, only with an i2c driver
that requests a gpio irq. That works because when the i2c bus gets
removed the i2c device gets removed as well and that drops the
requested irq which frees the gpio.

I do see your point with exporting a gpio via sysfs. So I will drop
the remove retry from the patch.

However, I think the above mentioned patch is worth merging as it is
simple enough and it fixes a couple of issues in the gpio remove path.
But I guess we can discuss this in that thread, when Linus W gets to
it.

And thanks a lot for spending so much time on reviewing these patches.
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