Re: [PATCH 1/4] PM / tracing: Add pm_qos_update_target/flags tracepoints

[Keun-O Park <keun-o.park@windriver.com>]

2013년 06월 20일 21:35, Steven Rostedt 쓴 글:
> On Thu, 2013-06-20 at 13:56 +0900, kpark3469@gmail.com wrote:
>
>> +DEFINE_EVENT_PRINT(pm_qos_update, pm_qos_update_flags,
>> +
>> +	TP_PROTO(enum pm_qos_req_action action, int prev_value, int curr_value),
>> +
>> +	TP_ARGS(action, prev_value, curr_value),
>> +
>> +	TP_printk("action=%s prev_value=0x%x curr_value=0x%x",
>> +		  (__entry->action == PM_QOS_ADD_REQ) ? "ADD_REQ" :
>> +		  (__entry->action == PM_QOS_UPDATE_REQ) ? "UPDATE_REQ" :
>> +		  (__entry->action == PM_QOS_REMOVE_REQ) ? "REMOVE_REQ" : "??",
>> +		  __entry->prev_value, __entry->curr_value)
>> +);
>>   #endif /* _TRACE_POWER_H */
> Nice! I believe you are the first one to add a new event using a
> DEFINE_EVENT_PRINT(). And you did it properly (almost, see below) :-)
>
> The only other use of that was by Li Zefan who converted an existing
> event to DEFINE_EVENT_PRINT().
>
> There's a helper function to convert numbers into strings:
>
> 	TP_printk("action=%s prev_value=0x%x curr_value=0x%x",
> 		__print_symbolic(__entry->action,
> 			{ PM_QOS_ADD_REQ,	"ADD_REQ" },
> 			{ PM_QOS_UPDATE_REQ,	"UPDATE_REQ" },
> 			{ PM_QOS_REMOVE_REQ,	"REMOVE_REQ" }),
> 		__entry->prev_value, __entry->curr_value)
>
> The advantage of using __print_symbolic() is that it allows both perf
> and trace-cmd to read this event properly. Their parsers are not full C
> parsers, and when you open code the the processing, they both will fail
> to parse how to read the output, and will just default to printing the
> fields via their raw numbers.
>
> Another advantage is if the __entry->action is not one of the defined
> fields, instead of outputting "??" it will output the number in hex. Say
> if __entry->action is 0x123, the __print_symbolic will return "0x123" as
> a string and that will be shown to the user, letting you know the actual
> value of the field that was unknown.
>
> -- Steve
>
>
>

Thanks Steve. I modified codes to use __print_symbolic following your 
recommendation.

-- Sahara