Re: [Regression] Changes to i2c-piix4.c initialisation prevent loading of sp5100_tco watchdog driver on AMD SB800 chipset

From: Guenter Roeck <linux@roeck-us.net>
To: Boszormenyi Zoltan <zboszor@pr.hu>
Cc: Paul Menzel <paulepanter@users.sourceforge.net>,
	Wolfram Sang <wsa@the-dreams.de>,
	Christian Fetzer <fetzer.ch@gmail.com>,
	Jean Delvare <jdelvare@suse.com>,
	linux-i2c@vger.kernel.org, linux-watchdog@vger.kernel.org,
	853122@bugs.debian.org, Wim Van Sebroeck <wim@iguana.be>,
	Tim Small <tim@seoss.co.uk>,
	Nehal Shah <nehal-bakulchandra.shah@amd.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Thomas Brandon <tbrandonau@gmail.com>,
	Eddi De Pieri <eddi@depieri.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [Regression] Changes to i2c-piix4.c initialisation prevent loading of sp5100_tco watchdog driver on AMD SB800 chipset
Date: Sat, 1 Apr 2017 06:32:37 -0700	[thread overview]
Message-ID: <0b32728a-f545-be43-2870-94688f1f9da5@roeck-us.net> (raw)
In-Reply-To: <efce69fc-3899-43f4-c8ee-12b78a571e5a@pr.hu>

On 04/01/2017 03:13 AM, Boszormenyi Zoltan wrote:
> 2017-03-31 17:05 keltezéssel, Guenter Roeck írta:
>> On Fri, Mar 31, 2017 at 04:46:02PM +0200, Boszormenyi Zoltan wrote:
>>> 2017-03-31 14:49 keltezéssel, Guenter Roeck írta:
>>>> request_muxed_region() can fail, and literally every other driver
>>>> using it checks for that failure. Please do the same.
>>>
>>> In what circumstances can request_muxed_region() fail? As far as
>>> I can see, only if two drivers use the same I/O port base and the
>>> already present region did not use IORESOURCE_MUXED which is
>>> not the case here. When request_muxed_region() is used consistently,
>>> subsequent requests are put on a wait queue and the first one is
>>> woken up when the region is released. So, it's basically a mutex.
>>> Am I missing something here?
>>>
>>
>> Yes. failure to allocate the resource is one.
>
> So, a common mutex should be used.
>

Just because you don't want to check for errors ?

I am not on favor of your new solution. I think it violates layering all over
the place, and I dislike the idea of having a global mutex as you propose.
I won't shut it down, but I'll let others provide feedback on your new series
of patches.

Guenter

> I have also added synchronization to the USB PCI quirks code and
> have split the patch into three pieces now (USB quirks, i2c-piix4 and
> sp5100_tco) and they were sent to the relevant mailing lists.
>
> I don't know which subsystem wants to take it, all 3 patches are
> needed at once.
>
> Best regards,
> Zoltán Böszörményi
>