linux-kernel - Re: [PATCH V5 2/2] soc: qcom: aoss: Add debugfs entry

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Message-ID: <CAE-0n52YXvTzvK4B3Aggg1fcRyjy=+HzNADP315-J0iJ8bMWUQ@mail.gmail.com>
Date:   Mon, 30 Aug 2021 16:01:12 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Deepak Kumar Singh <deesin@...eaurora.org>,
        bjorn.andersson@...aro.org, clew@...eaurora.org,
        sibis@...eaurora.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, Andy Gross <agross@...nel.org>
Subject: Re: [PATCH V5 2/2] soc: qcom: aoss: Add debugfs entry

Quoting Deepak Kumar Singh (2021-08-30 04:46:53)
>
> On 8/5/2021 11:58 PM, Stephen Boyd wrote:
> > Quoting Deepak Kumar Singh (2021-08-05 04:12:54)
> >> It can be useful to control the different power states of various
> >> parts of hardware for device testing. Add a debugfs node for qmp so
> >> messages can be sent to aoss for debugging and testing purposes.
> > Is it ever useful after device testing? I'd prefer we not apply this
> > patch as it looks like testing code that won't ever be used after
> > developing this driver.
>
> This is not only for testing. Some user space clients can also use this
> to send messages to aoss.
>
> One such example is setting higher ddr frequency during boot and
> reducing it post boot from user space.
>

The debugfs file system should not be used by userspace to do things
like that. It's a debugging file system, not a configuration file
system. If you want to expose userspace control for this it needs to be
done in a different way.