Re: [PATCH 2/4] dev_printk: Add and use dev_no_printk()

[Andy Shevchenko]

On Wed, Feb 28, 2024 at 03:00:03PM +0100, Geert Uytterhoeven wrote:
> When printk-indexing is enabled, each dev_printk() invocation emits a
> pi_entry structure.  This is even true when the dev_printk() is
> protected by an always-false check, as is typically the case for debug
> messages: while the actual code to print the message is optimized out by
> the compiler, the pi_entry structure is still emitted.
> 
> Avoid emitting pi_entry structures for unavailable dev_printk() kernel
> messages by:
>   1. Introducing a dev_no_printk() helper, mimicked after the existing
>      no_printk() helper, which calls _dev_printk() instead of
>      dev_printk(),
>   2. Replacing all "if (0) dev_printk(...)" constructs by calls to the
>      new helper.
> 
> This reduces the size of an arm64 defconfig kernel with
> CONFIG_PRINTK_INDEX=y by 957 KiB.

..

> +/*
> + * Dummy dev_printk for disabled debugging statements to use whilst maintaining

dev_printk()

> + * gcc's format checking.
> + */
> +#define dev_no_printk(level, dev, fmt, ...)				\
> +	({								\
> +		if (0)							\
> +			_dev_printk(level, dev, fmt, ##__VA_ARGS__);	\
> +	})

-- 
With Best Regards,
Andy Shevchenko