linux-kernel - Re: [PATCH V2 19/30] coresight: etb10: implementing the setup

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Date:	Mon, 19 Oct 2015 16:44:34 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	gregkh@...uxfoundation.org, a.p.zijlstra@...llo.nl,
	acme@...nel.org, mingo@...hat.com, corbet@....net,
	nicolas.pitre@...aro.org
Cc:	adrian.hunter@...el.com, zhang.chunyan@...aro.org,
	mike.leach@....com, tor@...com, al.grant@....com,
	pawel.moll@....com, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	mathieu.poirier@...aro.org
Subject: Re: [PATCH V2 19/30] coresight: etb10: implementing the setup_aux() API

Mathieu Poirier <mathieu.poirier@...aro.org> writes:

> Adding an ETB10 specific auxiliary area setup operation to be
> used by the perf framework when events are initialised.
>
> Part of this operation involves modeling the mmap'ed area based
> on the specific ways a sink buffer gathers information.

It really doesn't seem to be ETB10 specific at all. When you add more
sinks, you'll probably end up copying this code every time.

Furthermore,

> +static void *etb_setup_aux(struct coresight_device *csdev, int cpu,
> +			   void **pages, int nr_pages, bool overwrite)
> +{
> +	int node, pg;
> +	struct cs_buffers *buf;
> +
> +	if (cpu == -1)
> +		cpu = smp_processor_id();
> +	node = cpu_to_node(cpu);
> +
> +	buf = kzalloc_node(offsetof(struct cs_buffers, addr[nr_pages]),
> +			   GFP_KERNEL, node);
> +	if (!buf)
> +		return NULL;
> +
> +	buf->snapshot = overwrite;
> +	buf->nr_pages = nr_pages;
> +
> +	/* Record information about buffers */
> +	for (pg = 0; pg < buf->nr_pages; pg++)
> +		buf->addr[pg] = pages[pg];
> +
> +	return buf;
> +}
> +

this one is so generic that I'm tempted to move this into perf's
ring_buffer code, because by the looks of it we'll need it pretty much
in every setup_aux().

Regards,
--
Alex
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