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Message-ID: <20240928162843.4eb63f29@jic23-huawei>
Date: Sat, 28 Sep 2024 16:28:43 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Matteo Martelli <matteomartelli3@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Jonathan Cameron
<Jonathan.Cameron@...wei.com>, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: pac1921: remove unnecessary explicit casts
On Mon, 16 Sep 2024 14:00:05 +0200
Matteo Martelli <matteomartelli3@...il.com> wrote:
> Many explicit casts were introduced to address Wconversion and
> Wsign-compare warnings. Remove them to improve readability.
>
> Fixes: 371f778b83cd ("iio: adc: add support for pac1921")
No fixes tag on this one. Its not a bug, just a readability improvement.
> Signed-off-by: Matteo Martelli <matteomartelli3@...il.com>
There are a few cases in here where I think the cast is about ensuring
we don't overflow in the maths rather than for warning suppression.
We all love 32 bit architectures after all ;)
Jonathan
> ---
> Link: https://lore.kernel.org/linux-iio/1fa4ab12-0939-477d-bc92-306fd32e4fd9@stanley.mountain/
> ---
> drivers/iio/adc/pac1921.c | 43 +++++++++++++++++++++----------------------
> 1 file changed, 21 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/iio/adc/pac1921.c b/drivers/iio/adc/pac1921.c
> index 4c2a1c07bc39..de69a1619a9e 100644
> --- a/drivers/iio/adc/pac1921.c
> +++ b/drivers/iio/adc/pac1921.c
> @@ -240,8 +240,8 @@ static inline void pac1921_calc_scale(int dividend, int divisor, int *val,
> {
> s64 tmp;
>
> - tmp = div_s64(dividend * (s64)NANO, divisor);
> - *val = (int)div_s64_rem(tmp, NANO, val2);
> + tmp = div_s64(dividend * NANO, divisor);
For this one, NANO is an unsigned long and dividend just an int.
Either the s64 cast is needed because dividend * NANO might go out of
unsigned long range which might (I think) be 32 bit on a 32bit machine
or it doesn't. If it does, then you need the cast, if not you don't
need to use div_s64 as it's not that large.
> + *val = div_s64_rem(tmp, NANO, val2);
> }
>
> /*
> @@ -260,7 +260,7 @@ static void pac1921_calc_current_scales(struct pac1921_priv *priv)
> int max = (PAC1921_MAX_VSENSE_MV * MICRO) >> i;
> int vsense_lsb = DIV_ROUND_CLOSEST(max, PAC1921_RES_RESOLUTION);
>
> - pac1921_calc_scale(vsense_lsb, (int)priv->rshunt_uohm,
> + pac1921_calc_scale(vsense_lsb, priv->rshunt_uohm,
> &priv->current_scales[i][0],
> &priv->current_scales[i][1]);
> }
> @@ -314,7 +314,7 @@ static int pac1921_check_push_overflow(struct iio_dev *indio_dev, s64 timestamp)
> timestamp);
> }
>
> - priv->prev_ovf_flags = (u8)flags;
> + priv->prev_ovf_flags = flags;
>
> return 0;
> }
> @@ -329,8 +329,7 @@ static int pac1921_check_push_overflow(struct iio_dev *indio_dev, s64 timestamp)
> static int pac1921_read_res(struct pac1921_priv *priv, unsigned long reg,
> u16 *val)
> {
> - int ret = regmap_bulk_read(priv->regmap, (unsigned int)reg, val,
> - sizeof(*val));
> + int ret = regmap_bulk_read(priv->regmap, reg, val, sizeof(*val));
> if (ret)
> return ret;
>
> @@ -366,7 +365,7 @@ static int pac1921_read_raw(struct iio_dev *indio_dev,
> if (ret)
> return ret;
>
> - *val = (int)res_val;
> + *val = res_val;
>
> return IIO_VAL_INT;
> }
> @@ -397,13 +396,13 @@ static int pac1921_read_raw(struct iio_dev *indio_dev,
> int *curr_scale = priv->current_scales[priv->di_gain];
>
> /* Convert current_scale from INT_PLUS_NANO to INT */
> - s64 tmp = curr_scale[0] * (s64)NANO + curr_scale[1];
> + s64 tmp = curr_scale[0] * NANO + curr_scale[1];
Same potential issue as above. NANO and curr_scale might be 32 bit in which
case I believe this can overflow?
>
> /* Multiply by max_vbus (V) / dv_gain */
> - tmp *= PAC1921_MAX_VBUS_V >> (int)priv->dv_gain;
> + tmp *= PAC1921_MAX_VBUS_V >> priv->dv_gain;
>
> /* Convert back to INT_PLUS_NANO */
> - *val = (int)div_s64_rem(tmp, NANO, val2);
> + *val = div_s64_rem(tmp, NANO, val2);
>
> return IIO_VAL_INT_PLUS_NANO;
> }
...
> @@ -607,7 +606,7 @@ static int pac1921_update_int_num_samples(struct pac1921_priv *priv,
> if (ret < 0)
> return ret;
>
> - n_samples = (u8)ret;
> + n_samples = ret;
>
> if (priv->n_samples == n_samples)
> return 0;
> @@ -770,7 +769,7 @@ static ssize_t pac1921_read_shunt_resistor(struct iio_dev *indio_dev,
>
> guard(mutex)(&priv->lock);
>
> - vals[0] = (int)priv->rshunt_uohm;
> + vals[0] = priv->rshunt_uohm;
> vals[1] = MICRO;
>
> return iio_format_value(buf, IIO_VAL_FRACTIONAL, 1, vals);
> @@ -793,13 +792,13 @@ static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
> if (ret)
> return ret;
>
> - rshunt_uohm = (u32)val * MICRO + (u32)val_fract;
> + rshunt_uohm = val * MICRO + val_fract;
> if (rshunt_uohm == 0 || rshunt_uohm > INT_MAX)
> return -EINVAL;
>
> guard(mutex)(&priv->lock);
>
> - priv->rshunt_uohm = (u32)rshunt_uohm;
> + priv->rshunt_uohm = rshunt_uohm;
>
> pac1921_calc_current_scales(priv);
>
> @@ -1168,7 +1167,7 @@ static int pac1921_probe(struct i2c_client *client)
>
> priv->regmap = devm_regmap_init_i2c(client, &pac1921_regmap_config);
> if (IS_ERR(priv->regmap))
> - return dev_err_probe(dev, (int)PTR_ERR(priv->regmap),
> + return dev_err_probe(dev, PTR_ERR(priv->regmap),
> "Cannot initialize register map\n");
>
> devm_mutex_init(dev, &priv->lock);
> @@ -1191,7 +1190,7 @@ static int pac1921_probe(struct i2c_client *client)
>
> priv->vdd = devm_regulator_get(dev, "vdd");
> if (IS_ERR(priv->vdd))
> - return dev_err_probe(dev, (int)PTR_ERR(priv->vdd),
> + return dev_err_probe(dev, PTR_ERR(priv->vdd),
> "Cannot get vdd regulator\n");
>
> ret = regulator_enable(priv->vdd);
>
> ---
> base-commit: fec496684388685647652ab4213454fbabdab099
> change-id: 20240911-iio-pac1921-nocast-5c98cdeec059
>
> Best regards,
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