linux-kernel - Re: [PATCH v6 2/9] coresight: core: add a new API to retrieve the helper device

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Message-ID: <d8c6111f-28ba-4046-bcd5-67233e8ed4ca@arm.com>
Date: Wed, 3 Dec 2025 16:15:48 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Jie Gan <jie.gan@....qualcomm.com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
 Jinlong Mao <jinlong.mao@....qualcomm.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v6 2/9] coresight: core: add a new API to retrieve the
 helper device

On 08/09/2025 03:01, 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@...aro.org>
> Signed-off-by: Jie Gan <jie.gan@....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 042c4fa39e55..018b1119c48a 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -580,6 +580,41 @@ 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,

> +					      int type)

nit: enum coresight_dev_subtype_helper subtype

Otherwise looks good to me

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 == type) {
> +			mutex_unlock(&coresight_mutex);
> +			return helper;
> +		}
> +	}
> +	mutex_unlock(&coresight_mutex);
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(coresight_get_helper);
> +
>   /**
>    * coresight_get_in_port_dest: get the in-port number of the dest device
>    * that is connected to the src device.
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index e51b22b8ebde..f80122827934 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -158,6 +158,8 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
>   				   enum cs_mode mode);
>   int coresight_get_in_port_dest(struct coresight_device *src,
>   			       struct coresight_device *dest);
> +struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
> +					      int type);
>   
>   #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
>   int etm_readl_cp14(u32 off, unsigned int *val);
>