linux-kernel - Re: [PATCH 04/15] drivers: thermal: tsens: Add debugfs support

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Message-ID: <CAP245DV=pVF1oK2eFvK=iRng=Qxg=oDLWmHXBWtJH=VMxmmAvQ@mail.gmail.com>
Date:   Wed, 21 Aug 2019 18:25:39 +0530
From:   Amit Kucheria <amit.kucheria@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 04/15] drivers: thermal: tsens: Add debugfs support

On Mon, Aug 19, 2019 at 7:57 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Amit Kucheria (2019-08-19 00:58:23)
> > On Sat, Aug 17, 2019 at 9:37 AM Stephen Boyd <swboyd@...omium.org> wrote:
> > > > +
> > > > +static void tsens_debug_init(struct platform_device *pdev)
> > > > +{
> > > > +       struct tsens_priv *priv = platform_get_drvdata(pdev);
> > > > +       struct dentry *root, *file;
> > > > +
> > > > +       root = debugfs_lookup("tsens", NULL);
> > >
> > > Does this get created many times? Why doesn't tsens have a pointer to
> > > the root saved away somewhere globally?
> > >
> >
> > I guess we could call the statement below to create the root dir and
> > save away the pointer. I was trying to avoid #ifdef CONFIG_DEBUG_FS in
> > init_common() and instead have all of it in a single function that
> > gets called once per instance of the tsens controller.
>
> Or call this code many times and try to create the tsens node if
> !tsens_root exists where the variable is some global.

So I didn't quite understand this statement. The change you're
requesting is that the 'root' variable below should be a global?

tsens_probe() will get called twice on platforms with two instances of
the controller. So I will need to check some place if the 'tsens' root
dir already exists in debugfs, no? That is what I'm doing below.

> >
> > > > +       if (!root)
> > > > +               priv->debug_root = debugfs_create_dir("tsens", NULL);
> > > > +       else
> > > > +               priv->debug_root = root;
> > > > +