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    SubjectRe: [PATCH 56/62] watchdog: tangox_wdt: Convert to use device managed functions
    On Wed, Jan 11, 2017 at 03:39:17PM +0100, Uwe Kleine-König wrote:
    > On Wed, Jan 11, 2017 at 01:31:47PM +0100, Marc Gonzalez wrote:
    > > On 11/01/2017 11:52, Guenter Roeck wrote:
    > >
    > > > On 01/11/2017 01:07 AM, Marc Gonzalez wrote:
    > > >
    > > >>> @@ -134,12 +134,15 @@ static int tangox_wdt_probe(struct platform_device *pdev)
    > > >>> err = clk_prepare_enable(dev->clk);
    > > >>> if (err)
    > > >>> return err;
    > > >>> + err = devm_add_action_or_reset(&pdev->dev,
    > > >>> + (void(*)(void *))clk_disable_unprepare,
    > > >>> + dev->clk);
    > > >>> + if (err)
    > > >>> + return err;
    >
    > This looks wrong. There is no clk_unprepare_disable when
    > devm_add_action_or_reset fails.
    >
    That is what the _or_reset part of devm_add_action_or_reset() is for.

    > > >>
    > > >> Hello Guenter,
    > > >>
    > > >> I would rather avoid the function pointer cast.
    > > >> How about defining an auxiliary function for the cleanup action?
    > > >>
    > > >> clk_disable_unprepare() is static inline, so gcc will have to
    > > >> define an auxiliary function either way. What do you think?
    > > >
    > > > Not really. It would just make it more complicated to replace the
    > > > call with devm_clk_prepare_enable(), should it ever find its way
    > > > into the light of day.
    > >
    > > More complicated, because the cleanup function will have to be deleted later?
    > > The compiler will warn if someone forgets to do that.
    > >
    > > In my opinion, it's not a good idea to rely on the fact that casting
    > > void(*)(struct clk *clk) to void(*)(void *) is likely to work as expected
    > > on most platforms. (It has undefined behavior, strictly speaking.)
    >
    > I would expect it to work on all (Linux) platforms. Anyhow, I wonder if
    > there couldn't be found a better solution.
    >
    > If in the end it looks like the following that would be good I think:
    >
    > clk = devm_clk_get(...);
    > if (IS_ERR(clk))
    > ...
    >
    > ret = devm_clk_prepare_enable(clk)
    > if (ret)
    > return ret;
    >
    Yes, Dmitry tried to introduce devm_clk_prepare_enable() some 5 years ago,
    but the effort stalled.

    My take is that it will be easy to write another coccinelle script to convert
    to devm_clk_prepare_enable() once that is available, but I didn't see the point
    of waiting for that, especially since it may never happen.

    Guenter

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