Re: [PATCH v2 02/10] coresight: platform: Refactor graph endpoint parsing

[Mathieu Poirier]

Good afternoon,

On Thu, Jul 19, 2018 at 11:55:06AM +0100, Suzuki K Poulose wrote:
> Refactor the of graph endpoint parsing code, to make the error
> handling easier.
> 
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> Changes since v1:
>  - Splitted from the of_node refcounting fix, part1
> ---
>  drivers/hwtracing/coresight/of_coresight.c | 129 +++++++++++++++++------------
>  1 file changed, 75 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/of_coresight.c b/drivers/hwtracing/coresight/of_coresight.c
> index 6880bee..68faaf8 100644
> --- a/drivers/hwtracing/coresight/of_coresight.c
> +++ b/drivers/hwtracing/coresight/of_coresight.c
> @@ -114,17 +114,69 @@ int of_coresight_get_cpu(const struct device_node *node)
>  }
>  EXPORT_SYMBOL_GPL(of_coresight_get_cpu);
>  
> +/*
> + * of_coresight_parse_endpoint : Parse the given output endpoint @ep
> + * and fill the connection information in @pdata[*@i].
> + *
> + * Parses the local port, remote device name and the remote port. Also
> + * updates *@i to point to the next index, when an entry is added.
> + *
> + * Returns :
> + *	 0	- If the parsing completed without any fatal errors.
> + *	-Errno	- Fatal error, abort the scanning.
> + */
> +static int of_coresight_parse_endpoint(struct device *dev,
> +				       struct device_node *ep,
> +				       struct coresight_platform_data *pdata,
> +				       int *i)
> +{
> +	int ret = 0;
> +	struct of_endpoint endpoint, rendpoint;
> +	struct device_node *rparent = NULL;
> +	struct device_node *rport = NULL;
> +	struct device *rdev = NULL;
> +
> +	do {
> +		/* Parse the local port details */
> +		if (of_graph_parse_endpoint(ep, &endpoint))
> +			break;
> +		/*
> +		 * Get a handle on the remote port and parent
> +		 * attached to it.
> +		 */
> +		rparent = of_graph_get_remote_port_parent(ep);
> +		if (!rparent)
> +			break;
> +		rport = of_graph_get_remote_port(ep);
> +		if (!rport)
> +			break;
> +		if (of_graph_parse_endpoint(rport, &rendpoint))
> +			break;
> +
> +		/* If the remote device is not available, defer probing */
> +		rdev = of_coresight_get_endpoint_device(rparent);
> +		if (!rdev) {
> +			ret = -EPROBE_DEFER;
> +			break;
> +		}
> +
> +		pdata->outports[*i] = endpoint.port;
> +		pdata->child_names[*i] = dev_name(rdev);
> +		pdata->child_ports[*i] = rendpoint.id;
> +		/* Move the index */
> +		(*i)++;

Not a big fan, makes the code needlessly complex.  Incrementation of the index
can be done in the while loop of of_get_coresight_platform_data().  See below.

> +	} while (0);
> +
> +	return ret;
> +}
> +
>  struct coresight_platform_data *
>  of_get_coresight_platform_data(struct device *dev,
>  			       const struct device_node *node)
>  {
>  	int i = 0, ret = 0;
>  	struct coresight_platform_data *pdata;
> -	struct of_endpoint endpoint, rendpoint;
> -	struct device *rdev;
>  	struct device_node *ep = NULL;
> -	struct device_node *rparent = NULL;
> -	struct device_node *rport = NULL;
>  
>  	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
>  	if (!pdata)
> @@ -132,64 +184,33 @@ of_get_coresight_platform_data(struct device *dev,
>  
>  	/* Use device name as sysfs handle */
>  	pdata->name = dev_name(dev);
> +	pdata->cpu = of_coresight_get_cpu(node);
>  
>  	/* Get the number of input and output port for this component */
>  	of_coresight_get_ports(node, &pdata->nr_inport, &pdata->nr_outport);
>  
> -	if (pdata->nr_outport) {
> -		ret = of_coresight_alloc_memory(dev, pdata);
> +	/* If there are no output connections, we are done */
> +	if (!pdata->nr_outport)
> +		return pdata;
> +
> +	ret = of_coresight_alloc_memory(dev, pdata);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	/* Iterate through each port to discover topology */
> +	while ((ep = of_graph_get_next_endpoint(node, ep))) {
> +		/*
> +		 * No need to deal with input ports, processing for as
> +		 * processing for output ports will deal with them.
> +		 */

This comment has been broken for a while... It should read:

		/*
		 * No need to deal with input ports, as processing
		 * for output ports will deal with them.
		 */

> +		if (of_find_property(ep, "slave-mode", NULL))
> +			continue;
> +
> +		ret = of_coresight_parse_endpoint(dev, ep, pdata, &i);
>  		if (ret)
>  			return ERR_PTR(ret);

                i++;

> -
> -		/* Iterate through each port to discover topology */
> -		do {
> -			/* Get a handle on a port */
> -			ep = of_graph_get_next_endpoint(node, ep);
> -			if (!ep)
> -				break;
> -
> -			/*
> -			 * No need to deal with input ports, processing for as
> -			 * processing for output ports will deal with them.
> -			 */
> -			if (of_find_property(ep, "slave-mode", NULL))
> -				continue;
> -
> -			/* Get a handle on the local endpoint */
> -			ret = of_graph_parse_endpoint(ep, &endpoint);
> -
> -			if (ret)
> -				continue;
> -
> -			/* The local out port number */
> -			pdata->outports[i] = endpoint.port;
> -
> -			/*
> -			 * Get a handle on the remote port and parent
> -			 * attached to it.
> -			 */
> -			rparent = of_graph_get_remote_port_parent(ep);
> -			rport = of_graph_get_remote_port(ep);
> -
> -			if (!rparent || !rport)
> -				continue;
> -
> -			if (of_graph_parse_endpoint(rport, &rendpoint))
> -				continue;
> -
> -			rdev = of_coresight_get_endpoint_device(rparent);
> -			if (!rdev)
> -				return ERR_PTR(-EPROBE_DEFER);
> -
> -			pdata->child_names[i] = dev_name(rdev);
> -			pdata->child_ports[i] = rendpoint.id;
> -
> -			i++;
> -		} while (ep);
>  	}
>  
> -	pdata->cpu = of_coresight_get_cpu(node);
> -
>  	return pdata;
>  }
>  EXPORT_SYMBOL_GPL(of_get_coresight_platform_data);
> -- 
> 2.7.4
>