Re: [PATCH v2] drm: use ida to allocate connector ids

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jul 30, 2013 at 03:51:49AM -0400, Ilia Mirkin wrote:
> This makes it so that reloading a module does not cause all the
> connector ids to change, which are user-visible and sometimes used
> for configuration.
> 
> Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
> ---
> 
> v1 -> v2: correct loop condition... not sure how that slipped past
> me... the code started out by being <= DRM...VIRTUAL, I guess
> 
>  drivers/gpu/drm/drm_crtc.c | 61 +++++++++++++++++++++++++++++++---------------
>  drivers/gpu/drm/drm_drv.c  |  2 ++
>  include/drm/drm_crtc.h     |  2 ++
>  3 files changed, 46 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index fc83bb9..ed7599a 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -186,29 +186,29 @@ static const struct drm_prop_enum_list drm_dirty_info_enum_list[] = {
>  struct drm_conn_prop_enum_list {
>  	int type;
>  	const char *name;
> -	int count;
> +	struct ida count;

I'd rename this to something else. 'count' is just confusing.

>  };
>  
>  /*
>   * Connector and encoder types.
>   */
>  static struct drm_conn_prop_enum_list drm_connector_enum_list[] =
> -{	{ DRM_MODE_CONNECTOR_Unknown, "Unknown", 0 },
> -	{ DRM_MODE_CONNECTOR_VGA, "VGA", 0 },
> -	{ DRM_MODE_CONNECTOR_DVII, "DVI-I", 0 },
> -	{ DRM_MODE_CONNECTOR_DVID, "DVI-D", 0 },
> -	{ DRM_MODE_CONNECTOR_DVIA, "DVI-A", 0 },
> -	{ DRM_MODE_CONNECTOR_Composite, "Composite", 0 },
> -	{ DRM_MODE_CONNECTOR_SVIDEO, "SVIDEO", 0 },
> -	{ DRM_MODE_CONNECTOR_LVDS, "LVDS", 0 },
> -	{ DRM_MODE_CONNECTOR_Component, "Component", 0 },
> -	{ DRM_MODE_CONNECTOR_9PinDIN, "DIN", 0 },
> -	{ DRM_MODE_CONNECTOR_DisplayPort, "DP", 0 },
> -	{ DRM_MODE_CONNECTOR_HDMIA, "HDMI-A", 0 },
> -	{ DRM_MODE_CONNECTOR_HDMIB, "HDMI-B", 0 },
> -	{ DRM_MODE_CONNECTOR_TV, "TV", 0 },
> -	{ DRM_MODE_CONNECTOR_eDP, "eDP", 0 },
> -	{ DRM_MODE_CONNECTOR_VIRTUAL, "Virtual", 0},
> +{	{ DRM_MODE_CONNECTOR_Unknown, "Unknown" },
> +	{ DRM_MODE_CONNECTOR_VGA, "VGA" },
> +	{ DRM_MODE_CONNECTOR_DVII, "DVI-I" },
> +	{ DRM_MODE_CONNECTOR_DVID, "DVI-D" },
> +	{ DRM_MODE_CONNECTOR_DVIA, "DVI-A" },
> +	{ DRM_MODE_CONNECTOR_Composite, "Composite" },
> +	{ DRM_MODE_CONNECTOR_SVIDEO, "SVIDEO" },
> +	{ DRM_MODE_CONNECTOR_LVDS, "LVDS" },
> +	{ DRM_MODE_CONNECTOR_Component, "Component" },
> +	{ DRM_MODE_CONNECTOR_9PinDIN, "DIN" },
> +	{ DRM_MODE_CONNECTOR_DisplayPort, "DP" },
> +	{ DRM_MODE_CONNECTOR_HDMIA, "HDMI-A" },
> +	{ DRM_MODE_CONNECTOR_HDMIB, "HDMI-B" },
> +	{ DRM_MODE_CONNECTOR_TV, "TV" },
> +	{ DRM_MODE_CONNECTOR_eDP, "eDP" },
> +	{ DRM_MODE_CONNECTOR_VIRTUAL, "Virtual" },
>  };
>  
>  static const struct drm_prop_enum_list drm_encoder_enum_list[] =
> @@ -220,6 +220,22 @@ static const struct drm_prop_enum_list drm_encoder_enum_list[] =
>  	{ DRM_MODE_ENCODER_VIRTUAL, "Virtual" },
>  };
>  
> +void drm_connector_ida_init(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(drm_connector_enum_list); i++)
> +		ida_init(&drm_connector_enum_list[i].count);
> +}
> +
> +void drm_connector_ida_destroy(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(drm_connector_enum_list); i++)
> +		ida_destroy(&drm_connector_enum_list[i].count);
> +}
> +
>  const char *drm_get_encoder_name(const struct drm_encoder *encoder)
>  {
>  	static char buf[32];
> @@ -711,6 +727,9 @@ int drm_connector_init(struct drm_device *dev,
>  		       int connector_type)
>  {
>  	int ret;
> +	struct ida *count = &drm_connector_enum_list[connector_type].count;
> +
> +	ida_pre_get(count, GFP_KERNEL);
>  
>  	drm_modeset_lock_all(dev);
>  
> @@ -722,8 +741,9 @@ int drm_connector_init(struct drm_device *dev,
>  	connector->dev = dev;
>  	connector->funcs = funcs;
>  	connector->connector_type = connector_type;
> -	connector->connector_type_id =
> -		++drm_connector_enum_list[connector_type].count; /* TODO */
> +	ret = ida_get_new_above(count, 1, &connector->connector_type_id);
> +	if (ret)
> +		goto out;

Leak.

Also there's no retry loop w/ ida_pre_get() and since that's outside the
big kms lock, there could be a (small) chance that someone else already
consumed the allocation done in ida_pre_get(). And then we'll return
-EAGAIN which is a rather confusing error from an init function. I
guess you could just move the ida_pre_get() inside the kms lock and
avoid that race.

>  	INIT_LIST_HEAD(&connector->probed_modes);
>  	INIT_LIST_HEAD(&connector->modes);
>  	connector->edid_blob_ptr = NULL;
> @@ -764,6 +784,9 @@ void drm_connector_cleanup(struct drm_connector *connector)
>  	list_for_each_entry_safe(mode, t, &connector->modes, head)
>  		drm_mode_remove(connector, mode);
>  
> +	ida_remove(&drm_connector_enum_list[connector->connector_type].count,
> +		   connector->connector_type_id);
> +
>  	drm_mode_object_put(dev, &connector->base);
>  	list_del(&connector->head);
>  	dev->mode_config.num_connector--;
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 99fcd7c..00597a1 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -251,6 +251,7 @@ static int __init drm_core_init(void)
>  	int ret = -ENOMEM;
>  
>  	drm_global_init();
> +	drm_connector_ida_init();
>  	idr_init(&drm_minors_idr);
>  
>  	if (register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops))
> @@ -298,6 +299,7 @@ static void __exit drm_core_exit(void)
>  
>  	unregister_chrdev(DRM_MAJOR, "drm");
>  
> +	drm_connector_ida_destroy();
>  	idr_destroy(&drm_minors_idr);
>  }
>  
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index fa12a2f..effee9d 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -869,6 +869,8 @@ extern int drm_crtc_init(struct drm_device *dev,
>  			 const struct drm_crtc_funcs *funcs);
>  extern void drm_crtc_cleanup(struct drm_crtc *crtc);
>  
> +extern void drm_connector_ida_init(void);
> +extern void drm_connector_ida_destroy(void);
>  extern int drm_connector_init(struct drm_device *dev,
>  			      struct drm_connector *connector,
>  			      const struct drm_connector_funcs *funcs,
> -- 
> 1.8.1.5
> 
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-- 
Ville Syrjälä
Intel OTC