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

[Jie Gan <jie.gan@oss.qualcomm.com>]

On 5/11/2026 5:19 PM, Richard Cheng wrote:
> 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 <james.clark@linaro.org>
>> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
>> ---
>> Changes in v3:
>> - directly return the value for clear expression.
>> - Link to v2: https://lore.kernel.org/r/20260509-fix-trace-id-error-v2-1-c900bcbab3e9@oss.qualcomm.com
>>
>> Changes in v2:
>> - Refactor the coresight_path_assign_trace_id function.
>> - Link to v1: https://lore.kernel.org/r/20260508-fix-trace-id-error-v1-1-5f11a5456fdf@oss.qualcomm.com
>> ---
>>   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 ?
> 

Hi Richard,

The return value has been ignored in perf mode. It will introduce noisy 
by adding __must_check. So I think its better without __must_check?

Thanks,
Jie

> 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 <jie.gan@oss.qualcomm.com>
>>
>>