Subject: Re: [Regression] Changes to i2c-piix4.c initialisation prevent
 loading of sp5100_tco watchdog driver on AMD SB800 chipset
To: Guenter Roeck <linux@roeck-us.net>
References: <1485728348.3220.10.camel@googlemail.com>
 <1488530782.2457.41.camel@users.sourceforge.net>
 <20170303101702.GA1669@katana>
 <1490944639.2653.182.camel@users.sourceforge.net>
 <585a27fb-be15-df9f-00a9-bd4c3a654142@roeck-us.net>
 <d1152062-77c5-f1b7-6be9-d24ee221ada9@pr.hu>
 <20170331150524.GA31555@roeck-us.net>
 <efce69fc-3899-43f4-c8ee-12b78a571e5a@pr.hu>
 <0b32728a-f545-be43-2870-94688f1f9da5@roeck-us.net>
 <14472f36-3c8d-e77d-4077-bd0db3587281@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,
        Greg KH <greg@kroah.com>, Alan Stern <stern@rowland.harvard.edu>
From: Boszormenyi Zoltan <zboszor@pr.hu>
Message-ID: <dbf21d72-258c-7b6b-6145-8b84c8baad52@pr.hu>
Date: Sat, 1 Apr 2017 18:31:37 +0200
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2017-04-01 18:20 keltezéssel, Boszormenyi Zoltan írta:
> The best clean alternative would be add new resource handling infrastructure.
> * Expose the currently static alloc_resource() in kernel/resource.c
>   With this, driver initialization can allocate the resource once
>   for the lifetime of the driver and it it fails,

(unfinished sentence) then the failure is during driver initialization,
not during runtime, possibly days or weeks later.

> * Add a new insert_muxed_region() / __insert_muxed_region() function with
>   different semantics from request_muxed_region() / __request_region():
>   1 Accept a pointer to already allocated resource.
>   2 If the conflicting resource doesn't have IORESOURCE_MUXED set,
>     complain loudly in the syslog but still go into the wait queue.
>     The conflicting resource also has the name which can be printed
>     so the inconsistent resource / region usage can be fixed.
>   We can also just modify the __request_region() semantics, so:
>   1 It accepts a pointer to an allocated resource or NULL.
>     In the second case, the resource is allocated internally and can
>     still fail.
>   2 The above second point. But this may cause an error in code that
>     expects the old semantics.
>
> The window for request_muxed_region()+release_region() is so short
> that the requested I/O port range would not show up in /proc/ioports.
>
> All this would be to fix only 3 drivers in a no-error scenario and only
> achieving the functionality of a mutex seems to be overkill.
>
> Another alternative is to revert commit 2fee61d22e606fc99ade9079fda15fdee83ec33e
> that caused the regression in sp5100_tco in the first place.
>
> Best regards,
> Zoltán Böszörményi
>