Subject: Re: [PATCH v3] coresight: fix missing error code when trace ID is invalid

From: Richard Cheng <[email-masked]>
Date: Mon, 11 May 2026 17:19:23 +0800

On Mon, May 11, 2026 at 04:36:18PM +0800, Jie Gan wrote:
> When coresight_path_assign_trace_id() cannot assign a valid trace ID,
> coresight_enable_sysfs() takes the err_path goto with ret still 0,
> returning success to the caller despite no trace session being started.
> 
> Fix this by changing coresight_path_assign_trace_id() to return int.
> Move the IS_VALID_CS_TRACE_ID() check inside the function so it returns
> -EINVAL on failure and 0 on success. Update coresight_enable_sysfs() to
> check the return value directly instead of inspecting path->trace_id
> after the call.
> 
> The other caller in coresight-etm-perf.c discards the return value and
> continues to check path->trace_id via IS_VALID_CS_TRACE_ID() directly.
> This is unaffected: on failure path->trace_id is no longer written, so
> it remains 0, which IS_VALID_CS_TRACE_ID() rejects the same as before.
> 
> Fixes: d87d76d823d1 ("Coresight: Allocate trace ID after building the path")
> Reviewed-by: James Clark <[email-masked]>
> Signed-off-by: Jie Gan <[email-masked]>
> ---
> Changes in v3:
> - directly return the value for clear expression.
> - Link to v2: https://lore.kernel.org/r/[email-masked]
> 
> Changes in v2:
> - Refactor the coresight_path_assign_trace_id function.
> - Link to v1: https://lore.kernel.org/r/[email-masked]
> ---
>  drivers/hwtracing/coresight/coresight-core.c  | 14 ++++++++++----
>  drivers/hwtracing/coresight/coresight-priv.h  |  2 +-
>  drivers/hwtracing/coresight/coresight-sysfs.c |  4 ++--
>  3 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 46f247f73cf6..254db91a8ac9 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -739,8 +739,8 @@ static int coresight_get_trace_id(struct coresight_device *csdev,
>   * Call this after creating the path and before enabling it. This leaves
>   * the trace ID set on the path, or it remains 0 if it couldn't be assigned.
>   */
> -void coresight_path_assign_trace_id(struct coresight_path *path,
> -				    enum cs_mode mode)
> +int coresight_path_assign_trace_id(struct coresight_path *path,
> +				   enum cs_mode mode)
>  {
>  	struct coresight_device *sink = coresight_get_sink(path);
>  	struct coresight_node *nd;
> @@ -755,10 +755,16 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
>  		 * Non 0 is either success or fail.
>  		 */
>  		if (trace_id != 0) {
> -			path->trace_id = trace_id;
> -			return;
> +			if (IS_VALID_CS_TRACE_ID(trace_id)) {
> +				path->trace_id = trace_id;
> +				return 0;
> +			}
> +
> +			return -EINVAL;
>  		}
>  	}
> +
> +	return -EINVAL;
>  }
>  
>  /**
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 1ea882dffd70..34c7e792adbd 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -153,7 +153,7 @@ int coresight_make_links(struct coresight_device *orig,
>  void coresight_remove_links(struct coresight_device *orig,
>  			    struct coresight_connection *conn);
>  u32 coresight_get_sink_id(struct coresight_device *csdev);
> -void coresight_path_assign_trace_id(struct coresight_path *path,
> +int coresight_path_assign_trace_id(struct coresight_path *path,
>  				   enum cs_mode mode);

Hi Jie,

Thanks for your patch,

I'm thinking will "__must_check" should be added so in the future the next caller won't accidently
introduce this class of bug ?

Best regards,
Richard Cheng.

>  
>  #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
> diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
> index d2a6ed8bcc74..b6a870399e83 100644
> --- a/drivers/hwtracing/coresight/coresight-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-sysfs.c
> @@ -211,8 +211,8 @@ int coresight_enable_sysfs(struct coresight_device *csdev)
>  		goto out;
>  	}
>  
> -	coresight_path_assign_trace_id(path, CS_MODE_SYSFS);
> -	if (!IS_VALID_CS_TRACE_ID(path->trace_id))
> +	ret = coresight_path_assign_trace_id(path, CS_MODE_SYSFS);
> +	if (ret)
>  		goto err_path;
>  
>  	ret = coresight_enable_path(path, CS_MODE_SYSFS);
> 
> ---
> base-commit: 17c7841d09ee7d33557fd075562d9289b6018c90
> change-id: 20260508-fix-trace-id-error-dbfdd4d8f2d1
> 
> Best regards,
> -- 
> Jie Gan <[email-masked]>
> 
>