[for-next,13/23] USB: mtu3: tracing: Use the new __vstring() helper

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Instead of open coding a __dynamic_array() with a fixed length (which
defeats the purpose of the dynamic array in the first place). Use the new
__vstring() helper that will use a va_list and only write enough of the
string into the ring buffer that is needed.

Link: https://lkml.kernel.org/r/20220705224750.354926535@goodmis.org

Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-usb@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 drivers/usb/mtu3/mtu3_trace.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

On Fri, 2022-07-15 at 17:24 -0400, Steven Rostedt wrote:
> On Fri, 15 Jul 2022 18:01:44 +0800
> Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
> 
> >  irq/254-1120100-137     [000] d..1.   266.629662: mtu3_log:
> > 11201000.usb: ep0_state SETUPr-speed
> > 
> > "r-speed" seems the remain of last log;
> 
> I found an off-by-one bug in the vstring patch. I'll rebase, test and
> try
> again.
> 
> In the mean time, care to add this on top to make sure it's fixed?
> 
> Thanks!
> 
> -- Steve
> 
> diff --git a/include/linux/trace_events.h
> b/include/linux/trace_events.h
> index e6f8ba52a958..b18759a673c6 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -922,16 +922,16 @@ perf_trace_buf_submit(void *raw_data, int size,
> int rctx, u16 type,
>   * gcc warns that you can not use a va_list in an inlined
>   * function. But lets me make it into a macro :-/
>   */
> -#define __trace_event_vstr_len(fmt, va)		\
> -({						\
> -	va_list __ap;				\
> -	int __ret;				\
> -						\
> -	va_copy(__ap, *(va));			\
> -	__ret = vsnprintf(NULL, 0, fmt, __ap);	\
> -	va_end(__ap);				\
> -						\
> -	min(__ret, TRACE_EVENT_STR_MAX);	\
> +#define __trace_event_vstr_len(fmt, va)			\
> +({							\
> +	va_list __ap;					\
> +	int __ret;					\
> +							\
> +	va_copy(__ap, *(va));				\
> +	__ret = vsnprintf(NULL, 0, fmt, __ap) + 1;	\

It works fine now, thanks a lot

> +	va_end(__ap);					\
> +							\
> +	min(__ret, TRACE_EVENT_STR_MAX);		\
>  })
>  
>  #endif /* _LINUX_TRACE_EVENT_H */

On Fri, 2022-07-15 at 17:39 -0400, Steven Rostedt wrote:
> On Fri, 15 Jul 2022 14:32:05 +0800
> Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
> 
> > Can you help to remove macro "MTU3_MSG_MAX" and one blank line
> > after it
> > in this file, this macro is not used anymore after apply this
> > patch.
> 
> Care to send me a patch, and I'll just include it in my series?
Seems no need add another patch, just modify this patch as below:

diff --git a/drivers/usb/mtu3/mtu3_trace.h
b/drivers/usb/mtu3/mtu3_trace.h
index a09deae1146f..03d2a9bac27e 100644
--- a/drivers/usb/mtu3/mtu3_trace.h
+++ b/drivers/usb/mtu3/mtu3_trace.h
@@ -18,18 +18,16 @@

 #include "mtu3.h"

-#define MTU3_MSG_MAX   256
-
 TRACE_EVENT(mtu3_log,
        TP_PROTO(struct device *dev, struct va_format *vaf),
        TP_ARGS(dev, vaf),
        TP_STRUCT__entry(
                __string(name, dev_name(dev))
-               __dynamic_array(char, msg, MTU3_MSG_MAX)
+               __vstring(msg, vaf->fmt, vaf->va)
        ),
        TP_fast_assign(
                __assign_str(name, dev_name(dev));
-               vsnprintf(__get_str(msg), MTU3_MSG_MAX, vaf->fmt, *vaf-
>va);
+               __assign_vstr(msg, vaf->fmt, vaf->va);
        ),
        TP_printk("%s: %s", __get_str(name), __get_str(msg))
 );
> 

remove below two lines
"
-#define MTU3_MSG_MAX   256
-
"
Thanks

> -- Steve

On Tue, 19 Jul 2022 13:23:06 +0800
Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:

> > Care to send me a patch, and I'll just include it in my series?  
> Seems no need add another patch, just modify this patch as below:
> 
> diff --git a/drivers/usb/mtu3/mtu3_trace.h
> b/drivers/usb/mtu3/mtu3_trace.h
> index a09deae1146f..03d2a9bac27e 100644
> --- a/drivers/usb/mtu3/mtu3_trace.h
> +++ b/drivers/usb/mtu3/mtu3_trace.h
> @@ -18,18 +18,16 @@
> 
>  #include "mtu3.h"
> 
> -#define MTU3_MSG_MAX   256
> -
>  TRACE_EVENT(mtu3_log,
>         TP_PROTO(struct device *dev, struct va_format *vaf),
>         TP_ARGS(dev, vaf),
>         TP_STRUCT__entry(
>                 __string(name, dev_name(dev))
> -               __dynamic_array(char, msg, MTU3_MSG_MAX)
> +               __vstring(msg, vaf->fmt, vaf->va)
>         ),
>         TP_fast_assign(
>                 __assign_str(name, dev_name(dev));
> -               vsnprintf(__get_str(msg), MTU3_MSG_MAX, vaf->fmt, *vaf-
> >va);  
> +               __assign_vstr(msg, vaf->fmt, vaf->va);
>         ),
>         TP_printk("%s: %s", __get_str(name), __get_str(msg))
>  );
> >   
> 
> remove below two lines
> "
> -#define MTU3_MSG_MAX   256
> -

Fine.

Even though I already pushed to linux-next, I did something I seldom do. I
rebased my for-next branch and removed this patch.

I'll send a v2.

-- Steve