Re: [PATCH 1/9] iio: humidity: hts221: refactor write_with_mask code

[Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Sun,  9 Jul 2017 18:56:56 +0200
Lorenzo Bianconi <lorenzo.bianconi83-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Move bit-shift in hts221_write_with_mask() instead of coding
> the shift depth in the configured value. That change will be necessary
> to fix an issue in device power-down procedure
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi-qxv4g6HH51o@public.gmane.org>
A could of questions inline.  

Jonathan
> ---
>  drivers/iio/humidity/hts221_core.c | 74 +++++++++++++++++---------------------
>  1 file changed, 32 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
> index a56da3999e00..f5181e4e1eff 100644
> --- a/drivers/iio/humidity/hts221_core.c
> +++ b/drivers/iio/humidity/hts221_core.c
> @@ -32,30 +32,12 @@
>  #define HTS221_HUMIDITY_AVG_MASK	0x07
>  #define HTS221_TEMP_AVG_MASK		0x38
>  
> -#define HTS221_ODR_MASK			0x87
> +#define HTS221_ODR_MASK			0x03
>  #define HTS221_BDU_MASK			BIT(2)
> +#define HTS221_ENABLE_MASK		BIT(7)
>  
>  #define HTS221_DRDY_MASK		BIT(2)
>  
> -#define HTS221_ENABLE_SENSOR		BIT(7)
> -
> -#define HTS221_HUMIDITY_AVG_4		0x00 /* 0.4 %RH */
> -#define HTS221_HUMIDITY_AVG_8		0x01 /* 0.3 %RH */
> -#define HTS221_HUMIDITY_AVG_16		0x02 /* 0.2 %RH */
> -#define HTS221_HUMIDITY_AVG_32		0x03 /* 0.15 %RH */
> -#define HTS221_HUMIDITY_AVG_64		0x04 /* 0.1 %RH */
> -#define HTS221_HUMIDITY_AVG_128		0x05 /* 0.07 %RH */
> -#define HTS221_HUMIDITY_AVG_256		0x06 /* 0.05 %RH */
> -#define HTS221_HUMIDITY_AVG_512		0x07 /* 0.03 %RH */
> -
> -#define HTS221_TEMP_AVG_2		0x00 /* 0.08 degC */
> -#define HTS221_TEMP_AVG_4		0x08 /* 0.05 degC */
> -#define HTS221_TEMP_AVG_8		0x10 /* 0.04 degC */
> -#define HTS221_TEMP_AVG_16		0x18 /* 0.03 degC */
> -#define HTS221_TEMP_AVG_32		0x20 /* 0.02 degC */
> -#define HTS221_TEMP_AVG_64		0x28 /* 0.015 degC */
> -#define HTS221_TEMP_AVG_128		0x30 /* 0.01 degC */
> -#define HTS221_TEMP_AVG_256		0x38 /* 0.007 degC */
>  
>  /* calibration registers */
>  #define HTS221_REG_0RH_CAL_X_H		0x36
> @@ -90,28 +72,28 @@ static const struct hts221_avg hts221_avg_list[] = {
>  		.addr = HTS221_REG_AVG_ADDR,
>  		.mask = HTS221_HUMIDITY_AVG_MASK,
>  		.avg_avl = {
> -			{ 4, HTS221_HUMIDITY_AVG_4 },
> -			{ 8, HTS221_HUMIDITY_AVG_8 },
> -			{ 16, HTS221_HUMIDITY_AVG_16 },
> -			{ 32, HTS221_HUMIDITY_AVG_32 },
> -			{ 64, HTS221_HUMIDITY_AVG_64 },
> -			{ 128, HTS221_HUMIDITY_AVG_128 },
> -			{ 256, HTS221_HUMIDITY_AVG_256 },
> -			{ 512, HTS221_HUMIDITY_AVG_512 },
> +			{   4, 0x0 }, /* 0.4 %RH */
> +			{   8, 0x1 }, /* 0.3 %RH */
> +			{  16, 0x2 }, /* 0.2 %RH */
> +			{  32, 0x3 }, /* 0.15 %RH */
> +			{  64, 0x4 }, /* 0.1 %RH */
> +			{ 128, 0x5 }, /* 0.07 %RH */
> +			{ 256, 0x6 }, /* 0.05 %RH */
> +			{ 512, 0x7 }, /* 0.03 %RH */
>  		},
>  	},
>  	{
>  		.addr = HTS221_REG_AVG_ADDR,
>  		.mask = HTS221_TEMP_AVG_MASK,
>  		.avg_avl = {
> -			{ 2, HTS221_TEMP_AVG_2 },
> -			{ 4, HTS221_TEMP_AVG_4 },
> -			{ 8, HTS221_TEMP_AVG_8 },
> -			{ 16, HTS221_TEMP_AVG_16 },
> -			{ 32, HTS221_TEMP_AVG_32 },
> -			{ 64, HTS221_TEMP_AVG_64 },
> -			{ 128, HTS221_TEMP_AVG_128 },
> -			{ 256, HTS221_TEMP_AVG_256 },
> +			{   2, 0x0 }, /* 0.08 degC */
> +			{   4, 0x1 }, /* 0.05 degC */
> +			{   8, 0x2 }, /* 0.04 degC */
> +			{  16, 0x3 }, /* 0.03 degC */
> +			{  32, 0x4 }, /* 0.02 degC */
> +			{  64, 0x5 }, /* 0.015 degC */
> +			{ 128, 0x6 }, /* 0.01 degC */
> +			{ 256, 0x7 }, /* 0.007 degC */
Could we potentially use the index directly here rather than
having to explicitly store it?  Would be more elegant perhaps..
>  		},
>  	},
>  };
> @@ -166,7 +148,7 @@ static int hts221_write_with_mask(struct hts221_hw *hw, u8 addr, u8 mask,
>  		goto unlock;
>  	}
>  
> -	data = (data & ~mask) | (val & mask);
> +	data = (data & ~mask) | ((val << __ffs(mask)) & mask);
>  
>  	err = hw->tf->write(hw->dev, addr, sizeof(data), &data);
>  	if (err < 0)
> @@ -201,11 +183,10 @@ static int hts221_check_whoami(struct hts221_hw *hw)
>  
>  int hts221_config_drdy(struct hts221_hw *hw, bool enable)
>  {
> -	u8 val = enable ? BIT(2) : 0;
>  	int err;
>  
>  	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL3_ADDR,
> -				     HTS221_DRDY_MASK, val);
> +				     HTS221_DRDY_MASK, enable);
>  
>  	return err < 0 ? err : 0;
>  }
> @@ -213,7 +194,6 @@ int hts221_config_drdy(struct hts221_hw *hw, bool enable)
>  static int hts221_update_odr(struct hts221_hw *hw, u8 odr)
>  {
>  	int i, err;
> -	u8 val;
>  
>  	for (i = 0; i < ARRAY_SIZE(hts221_odr_table); i++)
>  		if (hts221_odr_table[i].hz == odr)
> @@ -222,9 +202,19 @@ static int hts221_update_odr(struct hts221_hw *hw, u8 odr)
>  	if (i == ARRAY_SIZE(hts221_odr_table))
>  		return -EINVAL;
>  
> -	val = HTS221_ENABLE_SENSOR | HTS221_BDU_MASK | hts221_odr_table[i].val;
> +	/* enable Block Data Update */
> +	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
> +				     HTS221_BDU_MASK, 1);
> +	if (err < 0)
> +		return err;
> +
> +	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
> +				     HTS221_ODR_MASK, hts221_odr_table[i].val);
> +	if (err < 0)
> +		return err;
> +
>  	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
> -				     HTS221_ODR_MASK, val);
This original code looks like a bug given the odr mask should only
cover the odr bits, not the enable and bdu.

Am I missing something?

Taking one write and changing it to 3 isn't that nice, but I guess
we aren't in a fast path here so fair enough given the cleaner
resulting code.
> +				     HTS221_ENABLE_MASK, 1);
>  	if (err < 0)
>  		return err;
>