linux-kernel - Re: [PATCH] drm: Improve kerneldoc for drm_modeset

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Date:   Thu, 20 Jul 2017 20:39:27 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Liviu Dudau <Liviu.Dudau@....com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        DRI devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: Improve kerneldoc for drm_modeset_lock

On Thu, Jul 20, 2017 at 05:07:48PM +0100, Liviu Dudau wrote:
> Explain better when the drm_modeset_acquire_ctx parameter can
> be skipped for drm_modeset_lock() call.
> 
> Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>

Applied, thanks.
-Daniel

> ---
>  drivers/gpu/drm/drm_modeset_lock.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
> index 64ef09a6cccb..af4e906c630d 100644
> --- a/drivers/gpu/drm/drm_modeset_lock.c
> +++ b/drivers/gpu/drm/drm_modeset_lock.c
> @@ -52,7 +52,12 @@
>   *     drm_modeset_drop_locks(&ctx);
>   *     drm_modeset_acquire_fini(&ctx);
>   *
> - * On top of of these per-object locks using &ww_mutex there's also an overall
> + * If all that is needed is a single modeset lock, then the &struct
> + * drm_modeset_acquire_ctx is not needed and the locking can be simplified
> + * by passing a NULL instead of ctx in the drm_modeset_lock()
> + * call and, when done, by calling drm_modeset_unlock().
> + *
> + * On top of these per-object locks using &ww_mutex there's also an overall
>   * &drm_mode_config.mutex, for protecting everything else. Mostly this means
>   * probe state of connectors, and preventing hotplug add/removal of connectors.
>   *
> @@ -313,11 +318,14 @@ EXPORT_SYMBOL(drm_modeset_lock_init);
>   * @lock: lock to take
>   * @ctx: acquire ctx
>   *
> - * If ctx is not NULL, then its ww acquire context is used and the
> + * If @ctx is not NULL, then its ww acquire context is used and the
>   * lock will be tracked by the context and can be released by calling
>   * drm_modeset_drop_locks().  If -EDEADLK is returned, this means a
>   * deadlock scenario has been detected and it is an error to attempt
>   * to take any more locks without first calling drm_modeset_backoff().
> + *
> + * If @ctx is NULL then the function call behaves like a normal,
> + * non-nesting mutex_lock() call.
>   */
>  int drm_modeset_lock(struct drm_modeset_lock *lock,
>  		struct drm_modeset_acquire_ctx *ctx)
> -- 
> 2.13.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch