linux-kernel - Re: [PATCH v1 3/5] coresight: Explicitly use the parent device handler

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Message-ID: <64186261-3e65-45b5-a68c-8ec236a75f2f@arm.com>
Date: Thu, 11 Sep 2025 09:52:20 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Leo Yan <leo.yan@....com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Mao Jinlong <quic_jinlmao@...cinc.com>, coresight@...ts.linaro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/5] coresight: Explicitly use the parent device
 handler

On 12/05/2025 16:41, Leo Yan wrote:
> A CoreSight device is present on the CoreSight bus, and its device node
> in the DT binding is assigned as the parent device.  Comments are added
> to document this relationship.
> 
> The code is refined to explicitly use the parent device handle, making
> it more readable and clearly indicating which device handle is being
> used.
> 
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 3eacdcf638df..4f51ce152ac7 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -1313,9 +1313,13 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>   	csdev->access = desc->access;
>   	csdev->orphan = true;
>   
> +	/*
> +	 * 'csdev->dev' is a device present on the CoreSight bus. The device
> +	 * node in the device tree is assigned as the parent device.
> +	 */
> +	csdev->dev.parent = desc->dev;
>   	csdev->dev.type = &coresight_dev_type[desc->type];
>   	csdev->dev.groups = desc->groups;
> -	csdev->dev.parent = desc->dev;
>   	csdev->dev.release = coresight_device_release;
>   	csdev->dev.bus = &coresight_bustype;
>   
> @@ -1334,7 +1338,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>   	 * Hold the reference to our parent device. This will be
>   	 * dropped only in coresight_device_release().
>   	 */
> -	csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
> +	csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(csdev->dev.parent));
>   	dev_set_name(&csdev->dev, "%s", desc->name);
>   
>   	/*
> @@ -1393,7 +1397,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>   
>   err_out:
>   	/* Cleanup the connection information */
> -	coresight_release_platform_data(NULL, desc->dev, desc->pdata);
> +	coresight_release_platform_data(NULL, csdev->dev.parent, desc->pdata);

This may be problematic, as the csdev could be NULL ?

Suzuki

>   	return ERR_PTR(ret);
>   }
>   EXPORT_SYMBOL_GPL(coresight_register);