Re: [PATCH v2 1/2] tracing/events: make __string() more general
From: Steven Rostedt
Date: Tue May 26 2009 - 22:15:30 EST
On Wed, 27 May 2009, Li Zefan wrote:
> >> With __string(..., src), we need to have a source string, but sometimes no
> >> source string is available, and what we know is how big the string will be.
> >> Take block trace events for example, I want to convert an unsigned char array
> >> into a string, after this patch, this can be done this way:
> >> TP_STRUCT_entry(
> >> __string( cmd, rq->cmd_len * 3 )
> >> )
> >> TP_fast_assign(
> >> construct_str( cmd )
> > What does the construct_str do?
> Ah, it's pseudo code.. Should be construct_str(__entry->cmd, rq),
> this helper function convert rq->cmd (unsigned char) to a string of
> hex dump.
> No source string is available, so I'm not calling assign_str() in
OK, I think I have a better understanding of what you are doing.
But, I don't like changing the interface for string by adding that
"strlen" to all users. I find that very ugly.
Could we instead perhaps add a __dynamic_array? That would take a length,
and append itself to after the strings?
#define __dynamic_array(item, len) int __dyn_loc_##item;
#define __dynamic_array(item, len) int item;
#define __get_dynamic_array(item) \
((void *)__entry + __entry->__str_loc_##field
#define __dynamic_array(item, len) \
__str_offsets.item = __str_size + \
offsetof(typeof(*entry), __str_data); \
__str_size += len;
And so on. You should be able to do something like this, and make it more
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/