Re: [PATCH 3/8] spi: pl022: Let runtime PM callbacks be available for CONFIG_PM

[Josh Cartwright <joshc@codeaurora.org>]

(comments below only marginally related to this change)

On Thu, Feb 20, 2014 at 04:31:15PM +0100, Ulf Hansson wrote:
> Convert to the SET_PM_RUNTIME_PM macro while defining the runtime PM
> callbacks. This means the callbacks becomes available for both
> CONFIG_PM_SLEEP and CONFIG_PM_RUNTIME, which is needed to handle the
> combinations of these scenarios.
> 
> Cc: Mark Brown <broonie@kernel.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>  drivers/spi/spi-pl022.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/spi/spi-pl022.c b/drivers/spi/spi-pl022.c
> index 74a0729..6dfcabf 100644
> --- a/drivers/spi/spi-pl022.c
> +++ b/drivers/spi/spi-pl022.c
> @@ -2277,7 +2277,7 @@ pl022_remove(struct amba_device *adev)
>  	return 0;
>  }
>  
> -#if defined(CONFIG_SUSPEND) || defined(CONFIG_PM_RUNTIME)
> +#ifdef CONFIG_PM

I wish we could get rid of PM-related #ifdefery in drivers...

For what it's worth, while working on another project, I discovered that
using a ternary operator in initializers might actually be able to help
out a bit:

	/*
	 * Intended for use in static object initializers,
	 * assign_if(const_expr, function) evaluates to 'function' if
	 * 'const_expr', otherwise NULL.
	 *
	 * The type of the assign_if() expression is typeof(function),
	 * and therefore can provide typechecking regardless of
	 * 'const_expr'.
	 *
	 * gcc considers 'function' to be used and will not generate a
	 * 'defined but not used' when not 'const_expr', however, gcc is
	 * smart enough to eliminate 'function' if assign_if() is the
	 * only reference.
	 */
	#define assign_if(const_expr, function)			\
		((const_expr) ? function : NULL)

	#define assign_if_enabled(option, function)		\
		assign_if(IS_ENABLED(option), function)

	#define assign_if_rpm(function)				\
		assign_if_enabled(CONFIG_PM_RUNTIME, function)

	static int foo_runtime_suspend(struct device *dev)
	{
		return 0;
	}

	static struct dev_pm_ops foo_pm_ops = {
		.runtime_suspend	= assign_if_rpm(foo_runtime_suspend),
	};

So, in this example, wrapping the definition of foo_runtime_suspend in
#ifdef CONFIG_PM_RUNTIME is unnecessary, as gcc will not emit it if
!CONFIG_PM_RUNTIME is not set (at least from my experiments).

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