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Date:   Sat, 2 May 2020 17:40:10 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Rikard Falkeborn <rikard.falkeborn@...il.com>
Cc:     linux-iio@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: ltr501: Constify structs

On Sat,  2 May 2020 11:52:37 +0200
Rikard Falkeborn <rikard.falkeborn@...il.com> wrote:

> Constify some data structs that are never changed. In order to do so,
> also update a couple of functions that now need to accept pointers to
> const struct instead of struct. While at it, update a few more functions
> to accept pointers to const struct instead of pointers.
> 
> This allows the compiler to put more data in the code segment instead of
> the data segment, as seen by the output of the file command:
> 
> Before:
>    text    data     bss     dec     hex filename
>   27080    8144     192   35416    8a58 drivers/iio/light/ltr501.o
> 
> After:
>    text    data     bss     dec     hex filename
>   27688    7536     192   35416    8a58 drivers/iio/light/ltr501.o
> Signed-off-by: Rikard Falkeborn <rikard.falkeborn@...il.com>

Looks sensible to me.  Will leave it a few days to get Peter time to
sanity check if he wants to.

Thanks,

Jonathan

> ---
>  drivers/iio/light/ltr501.c | 39 +++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/iio/light/ltr501.c b/drivers/iio/light/ltr501.c
> index 0626927251bb..5a3fcb127cd2 100644
> --- a/drivers/iio/light/ltr501.c
> +++ b/drivers/iio/light/ltr501.c
> @@ -101,12 +101,12 @@ struct ltr501_gain {
>  	int uscale;
>  };
>  
> -static struct ltr501_gain ltr501_als_gain_tbl[] = {
> +static const struct ltr501_gain ltr501_als_gain_tbl[] = {
>  	{1, 0},
>  	{0, 5000},
>  };
>  
> -static struct ltr501_gain ltr559_als_gain_tbl[] = {
> +static const struct ltr501_gain ltr559_als_gain_tbl[] = {
>  	{1, 0},
>  	{0, 500000},
>  	{0, 250000},
> @@ -117,14 +117,14 @@ static struct ltr501_gain ltr559_als_gain_tbl[] = {
>  	{0, 10000},
>  };
>  
> -static struct ltr501_gain ltr501_ps_gain_tbl[] = {
> +static const struct ltr501_gain ltr501_ps_gain_tbl[] = {
>  	{1, 0},
>  	{0, 250000},
>  	{0, 125000},
>  	{0, 62500},
>  };
>  
> -static struct ltr501_gain ltr559_ps_gain_tbl[] = {
> +static const struct ltr501_gain ltr559_ps_gain_tbl[] = {
>  	{0, 62500}, /* x16 gain */
>  	{0, 31250}, /* x32 gain */
>  	{0, 15625}, /* bits X1 are for x64 gain */
> @@ -133,9 +133,9 @@ static struct ltr501_gain ltr559_ps_gain_tbl[] = {
>  
>  struct ltr501_chip_info {
>  	u8 partid;
> -	struct ltr501_gain *als_gain;
> +	const struct ltr501_gain *als_gain;
>  	int als_gain_tbl_size;
> -	struct ltr501_gain *ps_gain;
> +	const struct ltr501_gain *ps_gain;
>  	int ps_gain_tbl_size;
>  	u8 als_mode_active;
>  	u8 als_gain_mask;
> @@ -192,7 +192,7 @@ static int ltr501_match_samp_freq(const struct ltr501_samp_table *tab,
>  	return -EINVAL;
>  }
>  
> -static int ltr501_als_read_samp_freq(struct ltr501_data *data,
> +static int ltr501_als_read_samp_freq(const struct ltr501_data *data,
>  				     int *val, int *val2)
>  {
>  	int ret, i;
> @@ -210,7 +210,7 @@ static int ltr501_als_read_samp_freq(struct ltr501_data *data,
>  	return IIO_VAL_INT_PLUS_MICRO;
>  }
>  
> -static int ltr501_ps_read_samp_freq(struct ltr501_data *data,
> +static int ltr501_ps_read_samp_freq(const struct ltr501_data *data,
>  				    int *val, int *val2)
>  {
>  	int ret, i;
> @@ -266,7 +266,7 @@ static int ltr501_ps_write_samp_freq(struct ltr501_data *data,
>  	return ret;
>  }
>  
> -static int ltr501_als_read_samp_period(struct ltr501_data *data, int *val)
> +static int ltr501_als_read_samp_period(const struct ltr501_data *data, int *val)
>  {
>  	int ret, i;
>  
> @@ -282,7 +282,7 @@ static int ltr501_als_read_samp_period(struct ltr501_data *data, int *val)
>  	return IIO_VAL_INT;
>  }
>  
> -static int ltr501_ps_read_samp_period(struct ltr501_data *data, int *val)
> +static int ltr501_ps_read_samp_period(const struct ltr501_data *data, int *val)
>  {
>  	int ret, i;
>  
> @@ -321,7 +321,7 @@ static unsigned long ltr501_calculate_lux(u16 vis_data, u16 ir_data)
>  	return lux / 1000;
>  }
>  
> -static int ltr501_drdy(struct ltr501_data *data, u8 drdy_mask)
> +static int ltr501_drdy(const struct ltr501_data *data, u8 drdy_mask)
>  {
>  	int tries = 100;
>  	int ret, status;
> @@ -373,7 +373,8 @@ static int ltr501_set_it_time(struct ltr501_data *data, int it)
>  }
>  
>  /* read int time in micro seconds */
> -static int ltr501_read_it_time(struct ltr501_data *data, int *val, int *val2)
> +static int ltr501_read_it_time(const struct ltr501_data *data,
> +			       int *val, int *val2)
>  {
>  	int ret, index;
>  
> @@ -391,7 +392,7 @@ static int ltr501_read_it_time(struct ltr501_data *data, int *val, int *val2)
>  	return IIO_VAL_INT_PLUS_MICRO;
>  }
>  
> -static int ltr501_read_als(struct ltr501_data *data, __le16 buf[2])
> +static int ltr501_read_als(const struct ltr501_data *data, __le16 buf[2])
>  {
>  	int ret;
>  
> @@ -403,7 +404,7 @@ static int ltr501_read_als(struct ltr501_data *data, __le16 buf[2])
>  				buf, 2 * sizeof(__le16));
>  }
>  
> -static int ltr501_read_ps(struct ltr501_data *data)
> +static int ltr501_read_ps(const struct ltr501_data *data)
>  {
>  	int ret, status;
>  
> @@ -419,7 +420,7 @@ static int ltr501_read_ps(struct ltr501_data *data)
>  	return status;
>  }
>  
> -static int ltr501_read_intr_prst(struct ltr501_data *data,
> +static int ltr501_read_intr_prst(const struct ltr501_data *data,
>  				 enum iio_chan_type type,
>  				 int *val2)
>  {
> @@ -716,7 +717,7 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
>  	return -EINVAL;
>  }
>  
> -static int ltr501_get_gain_index(struct ltr501_gain *gain, int size,
> +static int ltr501_get_gain_index(const struct ltr501_gain *gain, int size,
>  				 int val, int val2)
>  {
>  	int i;
> @@ -848,14 +849,14 @@ static int ltr501_write_raw(struct iio_dev *indio_dev,
>  	return ret;
>  }
>  
> -static int ltr501_read_thresh(struct iio_dev *indio_dev,
> +static int ltr501_read_thresh(const struct iio_dev *indio_dev,
>  			      const struct iio_chan_spec *chan,
>  			      enum iio_event_type type,
>  			      enum iio_event_direction dir,
>  			      enum iio_event_info info,
>  			      int *val, int *val2)
>  {
> -	struct ltr501_data *data = iio_priv(indio_dev);
> +	const struct ltr501_data *data = iio_priv(indio_dev);
>  	int ret, thresh_data;
>  
>  	switch (chan->type) {
> @@ -1359,7 +1360,7 @@ static bool ltr501_is_volatile_reg(struct device *dev, unsigned int reg)
>  	}
>  }
>  
> -static struct regmap_config ltr501_regmap_config = {
> +static const struct regmap_config ltr501_regmap_config = {
>  	.name =  LTR501_REGMAP_NAME,
>  	.reg_bits = 8,
>  	.val_bits = 8,

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