Re: [PATCH v4 01/15] scripts: checkpatch: Add __aligned to the list of attribute notes

[Joe Perches]

On Sat, 2023-12-16 at 14:45 -0300, Marcelo Schmitt wrote:
> Checkpatch presumes attributes marked with __aligned(alignment) are part
> of a function declaration and throws a warning stating that those
> compiler attributes should have an identifier name which is not correct.
> Add __aligned compiler attributes to the list of attribute notes
> so they don't cause warnings anymore.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
> ---
> Any expression that evaluates to an integer that is a power of 2 can be
> within __aligned parenthesis.
> I can't see how we could use a regex to check code meets such constraint (if possible).

You can't because if a #define is used for the alignment
value it is not necessarily available to a patch fragment
or even a file if the #define is in an #include.

> Some additional exotic uses of __aligned are:
> drivers/net/wireless/quantenna/qtnfmac/bus.h:72:   char bus_priv[] __aligned(sizeof(void *));
> include/linux/netdevice.h:225:} __aligned(4 * sizeof(unsigned long)); 

Right, then there are random uses like:

drivers/firmware/qcom/qcom_qseecom_uefisecapp.c:		size_t __aligned;						\
drivers/firmware/qcom/qcom_qseecom_uefisecapp.c:			*__offset = __aligned;					\

so there's always some false positive/negative issue
with checkpatch.

Anyway:

Acked-by: Joe Perches <joe@xxxxxxxxxxx>

> 
> The regex
> 			__aligned\s*\(.*\)
> seems to match all use cases. 
> 
> We might not catch invalid arguments to __aligned, but it looks like making
> checkpath confidently report those wouldn't be feasible anyway.
> 
> The patch that would trigger the mentioned warning in now
> patch number 13 (iio: adc: Add support for AD7091R-8).
> 
>  scripts/checkpatch.pl | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 25fdb7fda112..d56c98146da3 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -512,6 +512,7 @@ our $Attribute	= qr{
>  			__ro_after_init|
>  			__kprobes|
>  			$InitAttribute|
> +			__aligned\s*\(.*\)|
>  			____cacheline_aligned|
>  			____cacheline_aligned_in_smp|
>  			____cacheline_internodealigned_in_smp|