Re: [ndctl PATCH v9 4/7] cxl/event_trace: add helpers to retrieve tep fields by type

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

On 2/29/24 6:31 PM, 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.
> 
> Since this is in preparation for adding a cxl_poison private parser
> for 'cxl list --media-errors' support, add those specific required
> types: u8, u32, u64, char*
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  cxl/event_trace.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++
>  cxl/event_trace.h | 10 ++++++-
>  2 files changed, 84 insertions(+), 1 deletion(-)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index bdad0c19dbd4..6cc9444f3204 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -15,6 +15,81 @@
>  #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;
> +}
> +
> +u64 cxl_get_field_u64(struct tep_event *event, struct tep_record *record,
> +		      const char *name)
> +{
> +	struct tep_format_field *f;
> +	unsigned char *val;
> +	int len;
> +
> +	f = __find_field(event, name);
> +	if (!f)
> +		return ULLONG_MAX;
> +
> +	val = tep_get_field_raw(NULL, event, f->name, record, &len, 0);
> +	if (!val)
> +		return ULLONG_MAX;
> +
> +	return *(u64 *)val;
> +}
> +
> +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);
> +}
> +
> +u32 cxl_get_field_u32(struct tep_event *event, struct tep_record *record,
> +		      const char *name)
> +{
> +	char *val;
> +
> +	val = cxl_get_field_string(event, record, name);
> +	if (!val)
> +		return UINT_MAX;
> +
> +	return *(u32 *)val;
> +}
> +
> +u8 cxl_get_field_u8(struct tep_event *event, struct tep_record *record,
> +		    const char *name)
> +{
> +	char *val;
> +
> +	val = cxl_get_field_string(event, record, name);
> +	if (!val)
> +		return UCHAR_MAX;
> +
> +	return *(u8 *)val;
> +}
> +
>  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..bbdea3b896e0 100644
> --- a/cxl/event_trace.h
> +++ b/cxl/event_trace.h
> @@ -5,6 +5,7 @@
>  
>  #include <json-c/json.h>
>  #include <ccan/list/list.h>
> +#include <ccan/short_types/short_types.h>
>  
>  struct jlist_node {
>  	struct json_object *jobj;
> @@ -25,5 +26,12 @@ 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);
> +u8 cxl_get_field_u8(struct tep_event *event, struct tep_record *record,
> +		    const char *name);
> +u32 cxl_get_field_u32(struct tep_event *event, struct tep_record *record,
> +		      const char *name);
> +u64 cxl_get_field_u64(struct tep_event *event, struct tep_record *record,
> +		      const char *name);
>  #endif