Re: [PATCH v6 4/8] drm: tda998x: use cec_notifier_conn_(un)register

[Russell King - ARM Linux admin]

On Tue, Aug 13, 2019 at 01:02:36PM +0200, Dariusz Marcinkiewicz wrote:
> Use the new cec_notifier_conn_(un)register() functions to
> (un)register the notifier for the HDMI connector, and fill
> in the cec_connector_info.
> 
> Changes since v2:
> 	- cec_notifier_phys_addr_invalidate where appropriate,
> 	- don't check for NULL notifier before calling
> 	cec_notifier_conn_unregister.
> Changes since v1:
> 	Add memory barrier to make sure that the notifier
> 	becomes visible to the irq thread once it is
> 	fully constructed.
> 
> Signed-off-by: Dariusz Marcinkiewicz <darekm@xxxxxxxxxx>
> Tested-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i2c/tda998x_drv.c | 33 +++++++++++++++++++++----------
>  1 file changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
> index 61e042918a7fc..19a63ee1b3f53 100644
> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
> @@ -804,9 +804,14 @@ static irqreturn_t tda998x_irq_thread(int irq, void *data)
>  			if (lvl & CEC_RXSHPDLEV_HPD) {
>  				tda998x_edid_delay_start(priv);
>  			} else {
> +				struct cec_notifier *notify;
> +
>  				schedule_work(&priv->detect_work);
> -				cec_notifier_set_phys_addr(priv->cec_notify,
> -						   CEC_PHYS_ADDR_INVALID);
> +
> +				notify = READ_ONCE(priv->cec_notify);
> +				if (notify)
> +					cec_notifier_phys_addr_invalidate(
> +							notify);
>  			}
>  
>  			handled = true;
> @@ -1331,6 +1336,8 @@ static int tda998x_connector_init(struct tda998x_priv *priv,
>  				  struct drm_device *drm)
>  {
>  	struct drm_connector *connector = &priv->connector;
> +	struct cec_connector_info conn_info;
> +	struct cec_notifier *notifier;
>  	int ret;
>  
>  	connector->interlace_allowed = 1;
> @@ -1347,6 +1354,19 @@ static int tda998x_connector_init(struct tda998x_priv *priv,
>  	if (ret)
>  		return ret;
>  
> +	cec_fill_conn_info_from_drm(&conn_info, connector);
> +
> +	notifier = cec_notifier_conn_register(priv->cec_glue.parent,
> +					      NULL, &conn_info);
> +	if (!notifier)
> +		return -ENOMEM;
> +	/*
> +	 * Make sure that tda998x_irq_thread does see the notifier
> +	 * when it fully constructed.
> +	 */
> +	smp_wmb();
> +	priv->cec_notify = notifier;

To nitpick, this comment and the following code do not go together.

I think what you actually mean is:

	 * Make sure that tda998x_irq_thread sees the notifier
	 * only after it is fully constructed.

> +
>  	drm_connector_attach_encoder(&priv->connector,
>  				     priv->bridge.encoder);
>  
> @@ -1790,8 +1810,7 @@ static void tda998x_destroy(struct device *dev)
>  
>  	i2c_unregister_device(priv->cec);
>  
> -	if (priv->cec_notify)
> -		cec_notifier_put(priv->cec_notify);
> +	cec_notifier_conn_unregister(priv->cec_notify);

This also doesn't make sense: tda998x_destroy() is the opposite of
tda998x_create().  However, tda998x_connector_destroy() is the
opposite of tda998x_connector_create().

By moving the CEC creation code into tda998x_connector_create(), you
are creating the possibility for the following sequence to mess up
CEC and leak:

	tda998x_create()
	tda998x_connector_create()
	tda998x_connector_destroy()
	tda998x_connector_create()
	tda998x_connector_destroy()
	tda998x_destroy()

Anything you create in tda998x_connector_create() must be cleaned up
by tda998x_connector_destroy().

>  }
>  
>  static int tda998x_create(struct device *dev)
> @@ -1916,12 +1935,6 @@ static int tda998x_create(struct device *dev)
>  		cec_write(priv, REG_CEC_RXSHPDINTENA, CEC_RXSHPDLEV_HPD);
>  	}
>  
> -	priv->cec_notify = cec_notifier_get(dev);
> -	if (!priv->cec_notify) {
> -		ret = -ENOMEM;
> -		goto fail;
> -	}
> -
>  	priv->cec_glue.parent = dev;
>  	priv->cec_glue.data = priv;
>  	priv->cec_glue.init = tda998x_cec_hook_init;
> -- 
> 2.23.0.rc1.153.gdeed80330f-goog
> 
> 

-- 
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