Re: [ndctl PATCH v10 3/7] cxl/event_trace: add a private context for private parsers

[Dan Williams <dan.j.williams@intel.com>]

alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> CXL event tracing provides helpers to iterate through a trace
> buffer and extract events of interest. It offers two parsing
> options: a default parser that adds every field of an event to
> a json object, and a private parsing option where the caller can
> parse each event as it wishes.
> 
> Although the private parser can do some conditional parsing based
> on field values, it has no method to receive additional information
> needed to make parsing decisions in the callback.
> 
> Add a private_ctx field to the existing 'struct event_context'.
> Replace the jlist_head parameter, used in the default parser,
> with the private_ctx.
> 
> This is in preparation for adding a private parser requiring
> additional context for cxl_poison events.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  cxl/event_trace.c | 2 +-
>  cxl/event_trace.h | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index 93a95f9729fd..bdad0c19dbd4 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -221,7 +221,7 @@ static int cxl_event_parse(struct tep_event *event, struct tep_record *record,
>  
>  	if (event_ctx->parse_event)
>  		return event_ctx->parse_event(event, record,
> -					      &event_ctx->jlist_head);
> +					      event_ctx->private_ctx);

Given ->parse_event() is already a method of an event_ctx object, might
as will pass the entirety of event_ctx to its own method as a typical
'this' pointer.

You could then also use container_of() to get to event_ctx creator data
and skip the type-unsafety of a 'void *' pointer. However, I say that
without having looked to see how feasible it is to wrap private data
around an event_ctx instance.