Re: [PATCH v1 3/3] perf cs-etm: Remove callback cs_etm_find_snapshot()

[Leo Yan]

Hi James,

On Tue, Jun 22, 2021 at 03:29:35PM +0100, James Clark wrote:
> 
> 
> On 28/05/2021 17:15, Leo Yan wrote:
> > The callback cs_etm_find_snapshot() is invoked for snapshot mode, its
> > main purpose is to find the correct AUX trace data and returns "head"
> > and "old" (we can call "old" as "old head") to the caller, the caller
> > __auxtrace_mmap__read() uses these two pointers to decide the AUX trace
> > data size.
> > 
> > cs_etm_find_snapshot() should be removed with below reasons:
> 
> Hi Leo,
> 
> I came across this other comment in coresight-tmc-etr.c that should probably
> be fixed up if we remove cs_etm_find_snapshot(). The same is duplicated in a
> few other files:
> 
> 	/*
> 	 * In snapshot mode we simply increment the head by the number of byte
> 	 * that were written.  User space function  cs_etm_find_snapshot() will
> 	 * figure out how many bytes to get from the AUX buffer based on the
> 	 * position of the head.
> 	 */
> 	if (etr_perf->snapshot)
> 		handle->head += size;

Good finding!  I will fix the comments in next version.

Thanks a lot for the reviewing and testing!

Leo