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SubjectRe: [PATCH 01/16] arch: x86: boot: Make function static and add function prototype

* Darshana Padmadas <darshanapadmadas@gmail.com> wrote:

> compressed/eboot.c defines an internal function
> setup_graphics(struct boot_params *boot_params). No
> other file refers to this function with the same
> parameters so make this function static.
>
> This eliminates the following warning:
>
> arch/x86/boot/compressed/eboot.c:1004:6: warning: no previous prototype for ‘setup_graphics’ [-Wmissing-prototypes]
>
> Also make_boot_params is declared only in this file and is used
> in some assembly. So add a prototype for this function.
>
> This eliminates the following warning:
>
> arch/x86/boot/compressed/eboot.c:1042:21: warning: no previous prototype for ‘make_boot_params’ [-Wmissing-prototypes]
>
> Signed-off-by: Darshana Padmadas <darshanapadmadas@gmail.com>
> ---
> arch/x86/boot/compressed/eboot.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index 92b9a5f..cb4ebab 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -1001,7 +1001,7 @@ free_handle:
> return status;
> }
>
> -void setup_graphics(struct boot_params *boot_params)
> +static void setup_graphics(struct boot_params *boot_params)

This category of change is good: making needlessly global functions
static is absolutely useful even if the kernel doesn't use the
-Wmissing-prototypes warning, because this allows the compiler to
potentially inline the function and thus reduce the size of the
kernel. (even if it's not inlined, it's a small reduction in kernel
image size.)

> {
> efi_guid_t graphics_proto = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
> struct screen_info *si;
> @@ -1039,6 +1039,9 @@ void setup_graphics(struct boot_params *boot_params)
> * The caller is responsible for filling out ->code32_start in the
> * returned boot_params.
> */
> +
> +struct boot_params *make_boot_params(struct efi_config *c);
> +
> struct boot_params *make_boot_params(struct efi_config *c)

This category of change is not so useful in that form: look at the
duplicated line in the .c file, it looks weird and not very useful at
first glance already.

The way this is typically solved in user-space projects that use -Wall
-Werror (such as tools/perf/) is to stick the external prototypes into
a proper header file.

If a function is global because it's only interfacing with assembly
code then put that into a comment before the prototype lines as well,
in the header file. In this case the extra prototypes are also useful:
they keep people modifying those functions informed and careful, as
changing the function parameters signature could break assembly code
without creating any obvious build time errors or warnings.

Thanks,

Ingo


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