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

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

On Thu, 2022-07-14 at 12:43 -0400, Steven Rostedt wrote:
> 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://urldefense.com/v3/__https://lkml.kernel.org/r/20220705224750.354926535@goodmis.org__;!!CTRNKA9wMg0ARbw!w8nx66BKDTtyusp5i2pyzOGNb-QyxIAWjoZwmSQY0zzor_rqvBgUm5__vKK98ApKcDic$
>  
> 
> 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(-)
> 
> diff --git a/drivers/usb/mtu3/mtu3_trace.h
> b/drivers/usb/mtu3/mtu3_trace.h
> index 1b897636daf2..ef3c17e2f8a6 100644
> --- a/drivers/usb/mtu3/mtu3_trace.h
> +++ b/drivers/usb/mtu3/mtu3_trace.h
> @@ -25,11 +25,11 @@ TRACE_EVENT(mtu3_log,
>  	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))
>  );

After apply this patch, encounter an issue, please check it

 irq/254-1120100-137     [000] d..1.   266.549473: mtu3_u2_common_isr:
(00000004)   RESET
 irq/254-1120100-137     [000] d..1.   266.629399: mtu3_log:
11201000.usb: link speed super-speed
 irq/254-1120100-137     [000] d..1.   266.629662: mtu3_log:
11201000.usb: ep0_state SETUPr-speed
 irq/254-1120100-137     [000] d..1.   266.629668: mtu3_handle_setup:
setup - 00 05 001c 0000 0000
 irq/254-1120100-137     [000] d..1.   266.629722: mtu3_log:
11201000.usb: ep0_state SETUPr-speed

without this patch:
 irq/254-1120100-135     [000] d..1.  1407.425550: mtu3_u2_common_isr:
(00000004)   RESET
 irq/254-1120100-135     [000] d..1.  1407.475295: mtu3_log:
11201000.usb: link speed super-speed
 irq/254-1120100-135     [000] d..1.  1407.477469: mtu3_log:
11201000.usb: ep0_state SETUP
 irq/254-1120100-135     [000] d..1.  1407.477476: mtu3_handle_setup:
setup - 00 05 001f 0000 0000
 irq/254-1120100-135     [000] d..1.  1407.477518: mtu3_log:
11201000.usb: ep0_state SETUP

the second and third lines with this patch:
 irq/254-1120100-137     [000] d..1.   266.629399: mtu3_log:
11201000.usb: link speed super-speed

 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;