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

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Date:	Tue, 20 Oct 2015 10:40:43 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>, a.p.zijlstra@...llo.nl,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...hat.com>, Jon Corbet <corbet@....net>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Chunyan Zhang <zhang.chunyan@...aro.org>,
	Mike Leach <mike.leach@....com>, Tor Jeremiassen <tor@...com>,
	Al Grant <al.grant@....com>,
	Paweł Moll <pawel.moll@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-doc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 19/30] coresight: etb10: implementing the setup_aux() API

On 19 October 2015 at 07:44, Alexander Shishkin
<alexander.shishkin@...ux.intel.com> wrote:
> 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.

That will depend on how that specific sinks work, but indeed, it is
pretty generic.

>
> 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().

It is tempting but I suggest we wait to see what kind of trend we get
before moving ahead with this.  There is always opportunity for
further consolidation should the need arise.

>
> Regards,
> --
> Alex
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