Re: [PATCH v8 2/8] coresight: core: add a new API to retrieve the helper device

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 11/12/2025 06:10, Jie Gan wrote:
> Retrieving the helper device of the specific coresight device based on
> its helper_subtype because a single coresight device may has multiple types
> of the helper devices.
> 
> Reviewed-by: Mike Leach <mike.leach@linaro.org>
> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 35 ++++++++++++++++++++++++++++
>   drivers/hwtracing/coresight/coresight-priv.h |  2 ++
>   2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 0e8448784c62..667883ccb4b7 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -585,6 +585,41 @@ struct coresight_device *coresight_get_sink(struct coresight_path *path)
>   }
>   EXPORT_SYMBOL_GPL(coresight_get_sink);
>   
> +/**
> + * coresight_get_helper: find the helper device of the assigned csdev.
> + *
> + * @csdev: The csdev the helper device is conntected to.
> + * @type:  helper_subtype of the expected helper device.
> + *
> + * Retrieve the helper device for the specific csdev based on its
> + * helper_subtype.
> + *
> + * Return: the helper's csdev upon success or NULL for fail.
> + */
> +struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
> +					      enum coresight_dev_subtype_helper subtype)

We have almost a similar function in coresight-core.c :

coresight_find_output_type(pdata, type, subtype).

Please could we reuse that, instead of adding similar funcitons ?

Please be careful about the mutex.

Suzuki

> +{
> +	int i;
> +	struct coresight_device *helper;
> +
> +	/* protect the connections */
> +	mutex_lock(&coresight_mutex);
> +	for (i = 0; i < csdev->pdata->nr_outconns; ++i) {
> +		helper = csdev->pdata->out_conns[i]->dest_dev;
> +		if (!helper || !coresight_is_helper(helper))
> +			continue;
> +
> +		if (helper->subtype.helper_subtype == subtype) {
> +			mutex_unlock(&coresight_mutex);
> +			return helper;
> +		}
> +	}
> +	mutex_unlock(&coresight_mutex);
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(coresight_get_helper);
> +
>   /**
>    * coresight_get_in_port: Find the input port number at @csdev where a @remote
>    * device is connected to.
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index cbf80b83e5ce..8e39a4dc7256 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -157,6 +157,8 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
>   				   enum cs_mode mode);
>   int coresight_get_in_port(struct coresight_device *csdev,
>   			  struct coresight_device *remote);
> +struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
> +					      enum coresight_dev_subtype_helper subtype);
>   
>   #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
>   int etm_readl_cp14(u32 off, unsigned int *val);
>