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

[James Clark]

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;

I'm still reviewing patch 1 and 2 as well.

James