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

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

[Jie Gan]

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);
 
 #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>

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

[Richard Cheng]

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 ?

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>
> 
> 

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

[Jie Gan]

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>
>>
>>

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

[Richard Cheng]

On Mon, May 11, 2026 at 05:27:10PM +0800, Jie Gan wrote:
> 
> 
> 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
>

Hi Jie,

Ahh thanks for the head up, my intention was adding a compile-time check there
to be safe, no need for __must_check here then.

If any new callers were to appear in the future we'll see how it goes.
Thanks.

Reviewed-by: Richard Cheng <icheng@nvidia.com>

Best regards,
Richard Cheng.
 
> > 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>
> > > 
> > > 
> 

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

[Leo Yan]

On Mon, May 11, 2026 at 05:27:10PM +0800, Jie Gan wrote:

[...]

> > > @@ -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;

I'd advocate a bit early exit style, like:

  /* 0 means the device has no ID assignment, so keep searching */
  if (trace_id == 0)
      continue;

  if (!IS_VALID_CS_TRACE_ID(trace_id))
      return -EINVAL;

  path->trace_id = trace_id;
  return 0;

Early exit can reduce indentation depth, and it handles simple cases
first and then the complex logic. In some cases (maye not this case),
we may benefit a bit from compiler optimization [1].

[1] https://xania.org/202512/18-partial-inlining

[...]

> 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?

Wouldn't it need to update perf mode as well?

Regarding __must_check, I searched Documentation but didn't find
guidance on when it should be used. I don't want to use this annotation
randomly (some functions use it and some not), this will be hard for
everyone to follow up.

IMO, it's fine not to use __must_check here. I would leave this to
Suzuki and other maintainers if have different opinions.

Thanks,
Leo

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

[Jie Gan]

On 5/11/2026 10:45 PM, Leo Yan wrote:
> On Mon, May 11, 2026 at 05:27:10PM +0800, Jie Gan wrote:
> 
> [...]
> 
>>>> @@ -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;
> 
> I'd advocate a bit early exit style, like:
> 
>    /* 0 means the device has no ID assignment, so keep searching */
>    if (trace_id == 0)
>        continue;
> 
>    if (!IS_VALID_CS_TRACE_ID(trace_id))
>        return -EINVAL;
> 
>    path->trace_id = trace_id;
>    return 0;
> 
> Early exit can reduce indentation depth, and it handles simple cases
> first and then the complex logic. In some cases (maye not this case),
> we may benefit a bit from compiler optimization [1].
> 

Thanks, that's a good suggestion and much simpler than my solution.

> [1] https://xania.org/202512/18-partial-inlining
> 
> [...]
> 
>> 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?
> 
> Wouldn't it need to update perf mode as well?

I will also update the perf mode for consistent usage.

Thanks,
Jie

> 
> Regarding __must_check, I searched Documentation but didn't find
> guidance on when it should be used. I don't want to use this annotation
> randomly (some functions use it and some not), this will be hard for
> everyone to follow up.
> 
> IMO, it's fine not to use __must_check here. I would leave this to
> Suzuki and other maintainers if have different opinions.
> 
> Thanks,
> Leo