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    SubjectRe: [PATCH 4/4] [RFC] hwmon: f71882fg: Add watchdog API for F71808E and F71889
    On Wed, Mar 24, 2010 at 03:51:51PM +0000, Alan Cox wrote:
    >> hold on the SIO port range. This would thus interfere with the
    >> operation of the f71882fg driver. I.e. it would prevent the device
    >> probing stage from working, thus preventing it from loading *after*
    >> my in-development watchdog driver.
    >
    > There are two ways to deal with that really
    >
    > ... snip ...
    >
    > 2. Fix the kernel request_resource stuff to support a sleeping non
    > exclusive resource so request/free of regions can be used as a resource
    > semaphore by co-operative devices.
    >
    > #2 is actually not hard but when I did the patch originally it then
    > wasn't needed by the driver I had in mind for other reasons.
    >
    > See http://groups.google.com/group/linux.kernel/msg/1425fc2aad32e6ea
    >
    > Maybe its worth resurrecting ?

    In this particular case I most definitely think it's worth resurrecting.
    Using your patch (I had to change the IORESOURCE_MUXED constant's value
    though) I can completely solve the I/O sharing issue for the f71882fg +
    watchdog case with only a single line modification to the f71882fg
    driver.

    One question regarding your patch though: how will it function when
    driver (A) locks an I/O region using request_region() then driver (B)
    comes along and tries to lock it using request_muxed_region()? One
    problem I imagine might occur is that driver (A)'s 'struct resource'
    doesn't have the IORESOURCE_MUXED flags set, thus simply won't wake up
    driver (B) on the 'muxed_resource_wait' queue.

    --
    Met vriendelijke groet,
    With kind regards,
    Giel van Schijndel
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