linux-kernel - Re: [RESEND PATCH V13 3/3] Input: new da7280 haptic driver

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Date:   Wed, 24 Jun 2020 15:37:26 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Roy Im <roy.im.opensource@...semi.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Brian Masney <masneyb@...tation.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>, Luca Weiss <luca@...tu.xyz>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Pascal PAILLET-LME <p.paillet@...com>,
        Rob Herring <robh@...nel.org>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Support Opensource <Support.Opensource@...semi.com>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>
Subject: Re: [RESEND PATCH V13 3/3] Input: new da7280 haptic driver

On Wed, Jun 24, 2020 at 12:04:24PM +0000, Roy Im wrote:
> Hello Uwe,
> 
> On Tue, June 23, 2020 11:41 PM, Uwe Kleine-König wrote:
> > 
> > Hello,
> > 
> > On Mon, Jun 15, 2020 at 08:40:23PM +0900, Roy Im wrote:
> > > Adds support for the Dialog DA7280 LRA/ERM Haptic Driver with multiple
> > > mode and integrated waveform memory and wideband support.
> > > It communicates via an I2C bus to the device.
> > >
> > > Signed-off-by: Roy Im <roy.im.opensource@...semi.com>
> > 
> > Just some picky comments below.
> > 
> > > +	error = pwm_apply_state(haptics->pwm_dev, &state);
> > > +	if (error)
> > > +		dev_err(haptics->dev,
> > > +			"failed to apply pwm state: %pE\n",
> > > +			ERR_PTR(error));
> > 
> > You can save some horizontal space here by dropping the \n after the first comma. (There are a few more occurences.)
> > 
> Ok, is this what you want?
> 	error = pwm_apply_state(haptics->pwm_dev, &state);
> 	if (error)
> 		dev_err(haptics->dev, "failed to apply pwm state: %pE\n",
> 			ERR_PTR(error));

Yes, that's what I meant.

> > > +	return error;
> > > +}
> > > +[...]
> > > +
> > > +		/* Sync up PWM state and ensure it is off. */
> > > +		pwm_init_state(haptics->pwm_dev, &state);
> > > +		state.enabled = false;
> > > +		error = pwm_apply_state(haptics->pwm_dev, &state);
> > > +		if (error) {
> > > +			dev_err(dev,
> > > +				"failed to apply initial PWM state: %pE\n",
> > > +				ERR_PTR(error));
> > > +			return error;
> > > +		}
> > > +
> > > +		/* Check PWM Period, it must be in 10k ~ 250kHz */
> > 
> > The unit of a PWM period is in (nano)seconds, to it cannot be in the range [10kHz, 250kHz]. (Is this too picky?)
> 
> No, it isn't. The 'Period' should be changed to 'frequency', I will fix this as below.
> 
> 		/* Check PWM frequency, valid range: 10k ~ 250kHz */

Much better.

> > 
> > > +		period2freq = 1000000 / state.period;
> > > +		if (period2freq < DA7280_MIN_PWM_FREQ_KHZ ||
> > > +		    period2freq > DA7280_MAX_PWM_FREQ_KHZ) {
> > > +			dev_err(dev, "Not supported PWM frequency(%d)\n",
> > > +				period2freq);
> > 
> > Doesn't the compiler warn here about period2freq being unsigned and %d being for signed int values?
> > 
> > For my (non-native) English ear s/Not supported/Unsupported/ sounds better. Also my eyes would be pleases by a space
> > before the opening brace.
> 
> I didn't see any warning message, but I will change/improve them to proper one and the log as below.
> 
> 		period2freq = 1000000 / state.period;
> 		if (period2freq < DA7280_MIN_PWM_FREQ_KHZ ||
> 		    period2freq > DA7280_MAX_PWM_FREQ_KHZ) {
> 			dev_err(dev, "Unsupported PWM frequency (%u)\n",
> 				period2freq);
> 			return -EINVAL;
> 		}
> If you look ok, let me update this so.

looks fine.

Note that you don't need the division if you check for:

	if (state.period > 100000 || state.period < 4000) {
		...

(maybe the compiler is already clever enough to get rid of the division
for you, but then the check is:

	if (state.period > 100000 || state.period < 3985) {
	
because of rounding errors.)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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