linux-kernel - Re: [Regression] Changes to i2c-piix4.c initialisation prevent loading of sp5100

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Date:   Sat, 1 Apr 2017 18:31:37 +0200
From:   Boszormenyi Zoltan <zboszor@...hu>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Paul Menzel <paulepanter@...rs.sourceforge.net>,
        Wolfram Sang <wsa@...-dreams.de>,
        Christian Fetzer <fetzer.ch@...il.com>,
        Jean Delvare <jdelvare@...e.com>, linux-i2c@...r.kernel.org,
        linux-watchdog@...r.kernel.org, 853122@...s.debian.org,
        Wim Van Sebroeck <wim@...ana.be>,
        Tim Small <tim@...ss.co.uk>,
        Nehal Shah <nehal-bakulchandra.shah@....com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thomas Brandon <tbrandonau@...il.com>,
        Eddi De Pieri <eddi@...ieri.net>,
        linux-kernel@...r.kernel.org, Greg KH <greg@...ah.com>,
        Alan Stern <stern@...land.harvard.edu>
Subject: Re: [Regression] Changes to i2c-piix4.c initialisation prevent
 loading of sp5100_tco watchdog driver on AMD SB800 chipset

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
>