linux-kernel - Re: [PATCH v1 1/1] drm/mm: Mark drm_mm_interval_tree*() functions with __maybe

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Message-ID: <87ttf2utg5.fsf@intel.com>
Date: Fri, 30 Aug 2024 14:43:38 +0300
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, Rodrigo Vivi
 <rodrigo.vivi@...el.com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David
 Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v1 1/1] drm/mm: Mark drm_mm_interval_tree*() functions
 with __maybe_unused

On Thu, 29 Aug 2024, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> The INTERVAL_TREE_DEFINE() uncoditionally provides a bunch of helper
> functions which in some cases may be not used. This, in particular,
> prevents kernel builds with `make W=1` and CONFIG_WERROR=y:
>
> .../drm/drm_mm.c:152:1: error: unused function 'drm_mm_interval_tree_insert' [-Werror,-Wunused-function]
>   152 | INTERVAL_TREE_DEFINE(struct drm_mm_node, rb,
>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   153 |                      u64, __subtree_last,
>       |                      ~~~~~~~~~~~~~~~~~~~~
>   154 |                      START, LAST, static inline, drm_mm_interval_tree)
>       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Fix this by marking drm_mm_interval_tree*() functions with __maybe_unused.
>
> Fixes: 202b52b7fbf7 ("drm: Track drm_mm nodes with an interval tree")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

As discussed in [1], the key combo is W=1 and Clang, which enables
detection for unused static inlines.

Reviewed-by: Jani Nikula <jani.nikula@...el.com>


BR,
Jani.


[1] https://lore.kernel.org/r/20240829155950.1141978-1-andriy.shevchenko@linux.intel.com


> ---
>  drivers/gpu/drm/drm_mm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index 5ace481c1901..1ed68d3cd80b 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -151,7 +151,7 @@ static void show_leaks(struct drm_mm *mm) { }
>  
>  INTERVAL_TREE_DEFINE(struct drm_mm_node, rb,
>  		     u64, __subtree_last,
> -		     START, LAST, static inline, drm_mm_interval_tree)
> +		     START, LAST, static inline __maybe_unused, drm_mm_interval_tree)
>  
>  struct drm_mm_node *
>  __drm_mm_interval_first(const struct drm_mm *mm, u64 start, u64 last)

-- 
Jani Nikula, Intel