Re: [PATCH v2] coresight: fix missing error code when trace ID is invalid

[Jie Gan]

On 5/11/2026 4:16 PM, James Clark wrote:
> On 09/05/2026 1:58 am, 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")
> > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxxxx
> > ---
> >   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..cabdc0c72f38 100644
> > --- a/drivers/hwtracing/coresight/coresight-core.c
> > +++ b/drivers/hwtracing/coresight/coresight-core.c
> > @@ -739,12 +739,12 @@ 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,
> > +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;
> > -    int trace_id;
> > +    int trace_id, ret = -EINVAL;
> >       list_for_each_entry(nd, &path->path_list, link) {
> >           /* Assign a trace ID to the path for the first device that 
> > wants to do it */
> > @@ -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;
> > +                ret = 0;
>
> Reviewed-by: James Clark <james.clark@xxxxxxxxxx>
>
> Minor nit, but just "return 0" here is a bit simpler.

Will remove the ret, and directly return the value for clearly expression.

Thanks,
Jie

> > +            }
> > +
> > +            return ret;
>
> And then "return -EINVAL" for these ones.
>
> >           }
> >       }
> > +
> > +    return ret; >   }
> >   /**
> > 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,