linux-kernel - Re: [PATCH v7 8/8] pwm: pca9685: Add error messages for failed regmap calls

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Message-ID: <20210407061619.fl6ffos6csvgtnjh@pengutronix.de>
Date:   Wed, 7 Apr 2021 08:16:19 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Clemens Gruber <clemens.gruber@...ruber.com>
Cc:     linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Sven Van Asbroeck <TheSven73@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 8/8] pwm: pca9685: Add error messages for failed
 regmap calls

On Tue, Apr 06, 2021 at 06:41:40PM +0200, Clemens Gruber wrote:
> Regmap operations can fail if the underlying subsystem is not working
> properly (e.g. hogged I2C bus, etc.)
> As this is useful information for the user, print an error message if it
> happens.
> Let probe fail if the first regmap_read or the first regmap_write fails.
> 
> Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
> ---
> Changes since v6:
> - Rebased
> 
>  drivers/pwm/pwm-pca9685.c | 83 ++++++++++++++++++++++++++++-----------
>  1 file changed, 59 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
> index cf0c98e4ef44..8a4993882b40 100644
> --- a/drivers/pwm/pwm-pca9685.c
> +++ b/drivers/pwm/pwm-pca9685.c
> @@ -107,6 +107,30 @@ static bool pca9685_prescaler_can_change(struct pca9685 *pca, int channel)
>  	return test_bit(channel, pca->pwms_enabled);
>  }
>  
> +static int pca9685_read_reg(struct pca9685 *pca, unsigned int reg, unsigned int *val)
> +{
> +	struct device *dev = pca->chip.dev;
> +	int err;
> +
> +	err = regmap_read(pca->regmap, reg, val);
> +	if (err != 0)
> +		dev_err(dev, "regmap_read of register 0x%x failed: %d\n", reg, err);

Please use %pe to emit the error code instead of %d.

> +
> +	return err;
> +}
> +
> +static int pca9685_write_reg(struct pca9685 *pca, unsigned int reg, unsigned int val)
> +{
> +	struct device *dev = pca->chip.dev;
> +	int err;
> +
> +	err = regmap_write(pca->regmap, reg, val);
> +	if (err != 0)
> +		dev_err(dev, "regmap_write to register 0x%x failed: %d\n", reg, err);
> +
> +	return err;
> +}
> +
>  /* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */
>  static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty)
>  {
> @@ -115,12 +139,12 @@ static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int
>  
>  	if (duty == 0) {
>  		/* Set the full OFF bit, which has the highest precedence */
> -		regmap_write(pca->regmap, REG_OFF_H(channel), LED_FULL);
> +		pca9685_write_reg(pca, REG_OFF_H(channel), LED_FULL);

You didn't check all return codes? How did you select the calls to
check?

Best regards
Uwe

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

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