linux-kernel - Re: [PATCH 1/4] coresight/etm4x: disallow altering config via sysfs while enabled

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Message-ID: <Z3+6kL7OGDX/pNul@e129823.arm.com>
Date: Thu, 9 Jan 2025 12:01:20 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: mike.leach@...aro.org, james.clark@...aro.org,
	alexander.shishkin@...ux.intel.com, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] coresight/etm4x: disallow altering config via sysfs
 while enabled

Hi Suzuki,

> Is it not better to have separate "configs" for perf and sysfs ?
> And etmX driver can populate the "running" config, based on the
> mode specific config. That way, the configs can be updated
> independently without affecting the running config or the perf one.
>

That was i've tried but I've accepted Mike's opinion that
it's enough to check whether CS_MODE_DISABLED via coresight_get_mode()
in *_store().

"the .._store functions in sysfs should use coresight_get_mode() to ensure
this is set to CS_MODE_DISABLED before altering the config,
which ensures that the trace system is inactive.
We don't' really care about reading the config if trace is running."

Thanks.