Re: [PATCH v4 02/10] cxl: add helper to parse through all current events

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Tue, 2022-11-08 at 11:29 -0700, Dave Jiang wrote:
> Add common function to iterate through and extract the events in the
> current trace buffer. The function uses tracefs_iterate_raw_events() from
> libtracefs to go through all the events loaded into a tep_handle. A
> callback is provided to the API call in order to parse the event. For cxl
> monitor, an array of interested "systems" is provided in order to filter

I couldn't tell what a 'system' means here - maybe clarify that?

> for the interested events.

s/interested events/events of interest/ ?

> 
> Tested-by: Alison Schofield <alison.schofield@intel.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  cxl/event_trace.c |   36 ++++++++++++++++++++++++++++++++++++
>  cxl/event_trace.h |   10 ++++++++++
>  cxl/meson.build   |    1 +
>  meson.build       |    2 ++
>  4 files changed, 49 insertions(+)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index 1b1b037e48bf..4667044e4a66 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -16,6 +16,7 @@
>  #include <libcxl.h>
>  #include <uuid/uuid.h>
>  #include <traceevent/event-parse.h>
> +#include <tracefs/tracefs.h>
>  #include "json.h"
>  #include "event_trace.h"
>  
> @@ -199,3 +200,38 @@ err_jevent:
>         free(jnode);
>         return rc;
>  }
> +
> +static int cxl_event_parse_cb(struct tep_event *event, struct tep_record *record,
> +               int cpu, void *ctx)

What does the _cb mean? I couldn't tell from what it's parsing what it
stands for - might be better to expand it?

> +{
> +       struct event_ctx *event_ctx = (struct event_ctx *)ctx;
> +
> +       /* Filter out all the events that the caller isn't interested in. */
> +       if (strcmp(event->system, event_ctx->system) != 0)
> +               return 0;
> +
> +       if (event_ctx->event_name) {
> +               if (strcmp(event->name, event_ctx->event_name) != 0)
> +                       return 0;
> +       }
> +
> +       if (event_ctx->parse_event)
> +               return event_ctx->parse_event(event, record, &event_ctx->jlist_head);
> +
> +       return cxl_event_to_json_callback(event, record, &event_ctx->jlist_head);
> +}
> +
> +int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx)
> +{
> +       struct tep_handle *tep;
> +       int rc;
> +
> +       tep = tracefs_local_events(NULL);
> +       if (!tep)
> +               return -ENOMEM;
> +
> +       rc = tracefs_iterate_raw_events(tep, inst, NULL, 0,
> +                       cxl_event_parse_cb, ectx);
> +       tep_free(tep);
> +       return rc;
> +}
> diff --git a/cxl/event_trace.h b/cxl/event_trace.h
> index 00975a0b5680..582882c1eb35 100644
> --- a/cxl/event_trace.h
> +++ b/cxl/event_trace.h
> @@ -11,4 +11,14 @@ struct jlist_node {
>         struct list_node list;
>  };
>  
> +struct event_ctx {
> +       const char *system;
> +       struct list_head jlist_head;
> +       const char *event_name;                                 /* optional */
> +       int (*parse_event)(struct tep_event *event, struct tep_record *record,
> +                          struct list_head *jlist_head);       /* optional */
> +};
> +
> +int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx);
> +
>  #endif
> diff --git a/cxl/meson.build b/cxl/meson.build
> index 8c7733431613..c59876262e76 100644
> --- a/cxl/meson.build
> +++ b/cxl/meson.build
> @@ -21,6 +21,7 @@ cxl_tool = executable('cxl',
>      json,
>      versiondep,
>      traceevent,
> +    tracefs,
>    ],
>    install : true,
>    install_dir : rootbindir,
> diff --git a/meson.build b/meson.build
> index f611e0bdd7f3..c204c8ac52de 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -143,6 +143,8 @@ libudev = dependency('libudev')
>  uuid = dependency('uuid')
>  json = dependency('json-c')
>  traceevent = dependency('libtraceevent')
> +tracefs = dependency('libtracefs')
> +
>  if get_option('docs').enabled()
>    if get_option('asciidoctor').enabled()
>      asciidoc = find_program('asciidoctor', required : true)
> 
>