linux-kernel - Re: [PATCH v2 3/4] drm/mode_object: add drm_mode_object_read

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Message-ID: <87wmhgfu2r.fsf@intel.com>
Date: Wed, 06 Nov 2024 14:03:08 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, Luca
 Ceresoli <luca.ceresoli@...tlin.com>
Subject: Re: [PATCH v2 3/4] drm/mode_object: add
 drm_mode_object_read_refcount()

On Wed, 06 Nov 2024, Luca Ceresoli <luca.ceresoli@...tlin.com> wrote:
> Add a wrapper to kref_read() just like the ones already in place for
> kref_get() and kref_put(). This will be used for sanity checks on object
> lifetime.
>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> ---
>  drivers/gpu/drm/drm_mode_object.c | 20 ++++++++++++++++++++
>  include/drm/drm_mode_object.h     |  1 +
>  2 files changed, 21 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
> index df4cc0e8e263d5887a799cf1a61d998234be7158..f990cc7e9b5d3bda3453123593314fa1ea2bf923 100644
> --- a/drivers/gpu/drm/drm_mode_object.c
> +++ b/drivers/gpu/drm/drm_mode_object.c
> @@ -217,6 +217,26 @@ void drm_mode_object_get(struct drm_mode_object *obj)
>  }
>  EXPORT_SYMBOL(drm_mode_object_get);
>  
> +/**
> + * drm_mode_object_get - read the refcount for a mode object
> + * @obj: DRM mode object
> + *
> + * This function returns the current object's refcount if it is a
> + * refcounted modeset object, or 0 on any other object.

Returns: The current object's ...

> + */
> +unsigned int drm_mode_object_read_refcount(struct drm_mode_object *obj)
> +{
> +	unsigned int refcount = 0;
> +
> +	if (obj->free_cb) {
> +		refcount = kref_read(&obj->refcount);
> +		DRM_DEBUG("OBJ ID: %d (%d)\n", obj->id, refcount);

Please ditch the debug.

> +	}
> +
> +	return refcount;
> +}
> +EXPORT_SYMBOL(drm_mode_object_read_refcount);
> +
>  /**
>   * drm_object_attach_property - attach a property to a modeset object
>   * @obj: drm modeset object
> diff --git a/include/drm/drm_mode_object.h b/include/drm/drm_mode_object.h
> index c68edbd126d04d51221f50aa2b4166475543b59f..3d2c739e703888bf4520c61594d480f128d50e56 100644
> --- a/include/drm/drm_mode_object.h
> +++ b/include/drm/drm_mode_object.h
> @@ -123,6 +123,7 @@ struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
>  					     uint32_t id, uint32_t type);
>  void drm_mode_object_get(struct drm_mode_object *obj);
>  void drm_mode_object_put(struct drm_mode_object *obj);
> +unsigned int drm_mode_object_read_refcount(struct drm_mode_object *obj);
>  
>  int drm_object_property_set_value(struct drm_mode_object *obj,
>  				  struct drm_property *property,

-- 
Jani Nikula, Intel