Re: [PATCH v6 4/7] cxl/event_trace: add helpers get_field_[string|data]()

[Dave Jiang <dave.jiang@intel.com>]

On 1/17/24 17:28, alison.schofield@intel.com wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> Add helpers to extract the value of an event record field given the
> field name. This is useful when the user knows the name and format
> of the field and simply needs to get it. Add signed and unsigned
> char* versions to support string and u64 data fields.
> 
> This is in preparation for adding a private parser of cxl_poison
> events.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  cxl/event_trace.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  cxl/event_trace.h |  5 ++++-
>  2 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index fbf7a77235ff..8d04d8d34194 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -15,6 +15,52 @@
>  #define _GNU_SOURCE
>  #include <string.h>
>  
> +static struct tep_format_field *__find_field(struct tep_event *event,
> +					     const char *name)
> +{
> +	struct tep_format_field **fields;
> +
> +	fields = tep_event_fields(event);
> +	if (!fields)
> +		return NULL;
> +
> +	for (int i = 0; fields[i]; i++) {
> +		struct tep_format_field *f = fields[i];
> +
> +		if (strcmp(f->name, name) != 0)
> +			continue;
> +
> +		return f;
> +	}
> +	return NULL;
> +}
> +
> +unsigned char *cxl_get_field_data(struct tep_event *event,
> +				  struct tep_record *record, const char *name)
> +{
> +	struct tep_format_field *f;
> +	int len;
> +
> +	f = __find_field(event, name);
> +	if (!f)
> +		return NULL;
> +
> +	return tep_get_field_raw(NULL, event, f->name, record, &len, 0);
> +}
> +
> +char *cxl_get_field_string(struct tep_event *event, struct tep_record *record,
> +			   const char *name)
> +{
> +	struct tep_format_field *f;
> +	int len;
> +
> +	f = __find_field(event, name);
> +	if (!f)
> +		return NULL;
> +
> +	return tep_get_field_raw(NULL, event, f->name, record, &len, 0);
> +}
> +
>  static struct json_object *num_to_json(void *num, int elem_size, unsigned long flags)
>  {
>  	bool sign = flags & TEP_FIELD_IS_SIGNED;
> diff --git a/cxl/event_trace.h b/cxl/event_trace.h
> index ec61962abbc6..6252f583097a 100644
> --- a/cxl/event_trace.h
> +++ b/cxl/event_trace.h
> @@ -25,5 +25,8 @@ int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx);
>  int cxl_event_tracing_enable(struct tracefs_instance *inst, const char *system,
>  		const char *event);
>  int cxl_event_tracing_disable(struct tracefs_instance *inst);
> -
> +char *cxl_get_field_string(struct tep_event *event, struct tep_record *record,
> +		const char *name);
> +unsigned char *cxl_get_field_data(struct tep_event *event,
> +		struct tep_record *record, const char *name);
>  #endif