> Subject: [PATCH 1/7] Make for_each_child_of_node() reference its args when CONFIG_OF=n
Nit: Documentation/SubmittingPatches, section 15. "subsystem: " is
missing from all patche titles.
On Fri, 03 Jan 2014 16:07:23 +0000 David Howells <dhowells@xxxxxxxxxx> wrote:
> Make for_each_child_of_node() reference its args when CONFIG_OF=n to avoid
> warnings like:
>
> drivers/leds/leds-pwm.c:88:22: warning: unused variable 'node' [-Wunused-variable]
> struct device_node *node = pdev->dev.of_node;
> ^
> ...
>
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -377,8 +377,13 @@ static inline bool of_have_populated_dt(void)
> return false;
> }
>
> +/* Kill an unused variable warning on a device_node pointer */
> +static inline void __of_use_dn(const struct device_node *np)
> +{
> +}
> +
> #define for_each_child_of_node(parent, child) \
> - while (0)
> + while (__of_use_dn(parent), __of_use_dn(child), 0)
>
> #define for_each_available_child_of_node(parent, child) \
> while (0)
That's a bit ugly. __maybe_unused fixes it appropriately but can't be
placed into the macro.
I wonder if we should instead generalise it to
static inline void reference_var_to_squish_gcc_warning(const void *p)
{
}
I guess not, until/unless we find other macros which need the same
treatment.
Yes, passing a var to an empty function suppresses the warning. But is
this intentional or a happy accident? Future gcc's could quite
legitimately be enhanced to detect that the arg is still unused and
then we'd need to find a new way of suppressing the warning, if such
exists.
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