Re: [PATCH v4 1/2] serial: qcom-geni: trace: Add tracepoint support for Qualcomm GENI serial

[Praveen Talari]

HI Steven,

On 29-05-2026 19:44, Steven Rostedt wrote:
> On Tue, 26 May 2026 23:07:39 +0530
> Praveen Talari <praveen.talari@xxxxxxxxxxxxxxxx> wrote:
>
> > +DECLARE_EVENT_CLASS(geni_serial_data,
> > +		    TP_PROTO(struct device *dev, const u8 *buf, unsigned int len),
> > +		    TP_ARGS(dev, buf, len),
> > +
> > +		    TP_STRUCT__entry(__string(name, dev_name(dev))
> > +				     __field(unsigned int, len)
> > +				     __dynamic_array(u8, data, len)
> > +		    ),
> > +
> > +		    TP_fast_assign(__assign_str(name);
> > +				   __entry->len = len;
> > +				   memcpy(__get_dynamic_array(data), buf, len);
> > +		    ),
> > +
> > +		    TP_printk("%s: len=%u data=%s",
> > +			      __get_str(name), __entry->len,
> > +			      __print_hex(__get_dynamic_array(data), __entry->len))
> > +);
> No need to save the length of the dynamic array in __entry->len because
> it's already saved in the metadata of the dynamic array that is stored
> on the buffer. Instead you can have:
>
> DECLARE_EVENT_CLASS(geni_serial_data,
> 		    TP_PROTO(struct device *dev, const u8 *buf, unsigned int len),
> 		    TP_ARGS(dev, buf, len),
>
> 		    TP_STRUCT__entry(__string(name, dev_name(dev))
> 				     __dynamic_array(u8, data, len)
> 		    ),
>
> 		    TP_fast_assign(__assign_str(name);
> 				   memcpy(__get_dynamic_array(data), buf, len);
> 		    ),
>
> 		    TP_printk("%s: len=%u data=%s",
> 			      __get_str(name), __entry->len,
> 			      __print_hex(__get_dynamic_array(data),
> 					__get_dynamic_array_len(data)))
> );
>
> That will save you 4 bytes per event on the ring buffer. And a few
> cycles not having to store the redundant information.

This patch has already been accepted and is available in linux-next.


Thanks,
Praveen Talari

> -- Steve