linux-kernel - Re: [PATCH 1/2] hwmon: pwm-fan: Add profile support and add remove module support

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Message-ID: <20200526134203.GA51584@roeck-us.net>
Date:   Tue, 26 May 2020 06:42:03 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Sandipan Patra <spatra@...dia.com>
Cc:     Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "kamil@...as.org" <kamil@...as.org>,
        "jdelvare@...e.com" <jdelvare@...e.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Bibek Basu <bbasu@...dia.com>,
        Bitan Biswas <bbiswas@...dia.com>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] hwmon: pwm-fan: Add profile support and add remove
 module support

On Tue, May 26, 2020 at 12:08:14PM +0000, Sandipan Patra wrote:
> Hi,
> 
> 
> > -----Original Message-----
> > From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
> > Sent: Tuesday, May 26, 2020 5:12 PM
> > To: Sandipan Patra <spatra@...dia.com>; Thierry Reding
> > <treding@...dia.com>; Jonathan Hunter <jonathanh@...dia.com>; u.kleine-
> > koenig@...gutronix.de; kamil@...as.org; jdelvare@...e.com;
> > robh+dt@...nel.org
> > Cc: Bibek Basu <bbasu@...dia.com>; Bitan Biswas <bbiswas@...dia.com>;
> > linux-pwm@...r.kernel.org; linux-hwmon@...r.kernel.org;
> > devicetree@...r.kernel.org; linux-tegra@...r.kernel.org; linux-
> > kernel@...r.kernel.org
> > Subject: Re: [PATCH 1/2] hwmon: pwm-fan: Add profile support and add remove
> > module support
> > 
> > External email: Use caution opening links or attachments
> > 
> > 
> > On 5/25/20 10:06 PM, Sandipan Patra wrote:
> > > This change has 2 parts:
> > > 1. Add support for profiles mode settings.
> > >     This allows different fan settings for trip point temp/hyst/pwm.
> > >     T194 has multiple fan-profiles support.
> > >
> > > 2. Add pwm-fan remove support. This is essential since the config is
> > >     tristate capable.
> > >
> > > Signed-off-by: Sandipan Patra <spatra@...dia.com>
> > > ---
> > >  drivers/hwmon/pwm-fan.c | 112
> > > ++++++++++++++++++++++++++++++++++++++++++------
> > >  1 file changed, 100 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c index
> > > 30b7b3e..26db589 100644
> > > --- a/drivers/hwmon/pwm-fan.c
> > > +++ b/drivers/hwmon/pwm-fan.c
> > 
> > [ ... ]
> > 
> > >
> > > +static int pwm_fan_remove(struct platform_device *pdev) {
> > > +     struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
> > > +     struct pwm_args args;
> > > +
> > > +     if (!ctx)
> > > +             return -EINVAL;
> > > +
> > > +     if (IS_ENABLED(CONFIG_THERMAL))
> > > +             thermal_cooling_device_unregister(ctx->cdev);
> > > +
> > > +     pwm_get_args(ctx->pwm, &args);
> > > +     pwm_config(ctx->pwm, 0, args.period);
> > > +     pwm_disable(ctx->pwm);
> > > +
> > > +     return 0;
> > > +}
> > > +
> > 
> > I don't think you actually tested this. I would suggest to make yourself familiar
> > with 'devm' functions and their use, and then resubmit.
> > 
> 
> Thanks Guenter.
> I missed to mention about devm while unregistering the cooling device.
> That would definitely cause a mistake in code. I am noting it for further patch.
> 
For that part, I am extremely surprised that it is not handled by the
thermal subsystem. Does each thermal driver need this kind of code ?

> For a better clarity, I will push next version of this patch to handle only multiple profiles support.
> "remove fan module" will be supported by a separate patch altogether.
> 

I asked you to look into "devm" functionality. I ask you again.
If you still think that a remove function is needed, I will require
detailed reasoning. Please be prepared to explain why devm functions
do not work for this driver.

Guenter