Re: [PATCH 3/5] iio: adis: Add adis_update_bits() APIs

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 25 Feb 2020 13:41:50 +0100
Nuno Sá <nuno.sa@analog.com> wrote:

> This patch adds a `regmap_update_bits()` like API to the ADIS library.
> It provides locked and unlocked variant.
> 
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Mostly fine, but I wonder if we can avoid the need to have comments
on handling of 1 and 8 byte values by explicitly avoiding them happening.

Thanks,

Jonathan

> ---
>  drivers/iio/imu/adis.c       | 26 +++++++++++++++
>  include/linux/iio/imu/adis.h | 61 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 87 insertions(+)
> 
> diff --git a/drivers/iio/imu/adis.c b/drivers/iio/imu/adis.c
> index a8afd01de4f3..fa0ee35d96f0 100644
> --- a/drivers/iio/imu/adis.c
> +++ b/drivers/iio/imu/adis.c
> @@ -223,6 +223,32 @@ int __adis_read_reg(struct adis *adis, unsigned int reg,
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(__adis_read_reg);
> +/**
> + * __adis_update_bits_base() - ADIS Update bits function - Unlocked version
> + * @adis: The adis device
> + * @reg: The address of the lower of the two registers
> + * @mask: Bitmask to change
> + * @val: Value to be written
> + * @size: Size of the register to update
> + *
> + * Updates the desired bits of @reg in accordance with @mask and @val.
> + */
> +int __adis_update_bits_base(struct adis *adis, unsigned int reg, const u32 mask,
> +			    const u32 val, u8 size)
> +{
> +	int ret;
> +	u32 __val;
> +
> +	ret = __adis_read_reg(adis, reg, &__val, size);
> +	if (ret)
> +		return ret;
> +
> +	__val &= ~mask;
> +	__val |= val & mask;
> +
> +	return __adis_write_reg(adis, reg, __val, size);
> +}
> +EXPORT_SYMBOL_GPL(__adis_update_bits_base);
>  
>  #ifdef CONFIG_DEBUG_FS
>  
> diff --git a/include/linux/iio/imu/adis.h b/include/linux/iio/imu/adis.h
> index b4c35d137e2a..07073f698718 100644
> --- a/include/linux/iio/imu/adis.h
> +++ b/include/linux/iio/imu/adis.h
> @@ -303,6 +303,67 @@ static inline int adis_read_reg_32(struct adis *adis, unsigned int reg,
>  	return ret;
>  }
>  
> +int __adis_update_bits_base(struct adis *adis, unsigned int reg, const u32 mask,
> +			    const u32 val, u8 size);
> +/**
> + * adis_update_bits_base() - ADIS Update bits function - Locked version
> + * @adis: The adis device
> + * @reg: The address of the lower of the two registers
> + * @mask: Bitmask to change
> + * @val: Value to be written
> + * @size: Size of the register to update
> + *
> + * Updates the desired bits of @reg in accordance with @mask and @val.
> + */
> +static inline int adis_update_bits_base(struct adis *adis, unsigned int reg,
> +					const u32 mask, const u32 val, u8 size)
> +{
> +	int ret;
> +
> +	mutex_lock(&adis->state_lock);
> +	ret = __adis_update_bits_base(adis, reg, mask, val, size);
> +	mutex_unlock(&adis->state_lock);
> +	return ret;
> +}
> +
> +/**
> + * adis_update_bits() - Wrapper macro for adis_update_bits_base - Locked version
> + * @adis: The adis device
> + * @reg: The address of the lower of the two registers
> + * @mask: Bitmask to change
> + * @val: Value to be written
> + *
> + * This macro evaluates the sizeof of @val at compile time and calls
> + * adis_update_bits_base() accordingly. Be aware that using MACROS/DEFINES for
> + * @val can lead to undesired behavior if the register to update is 16bit. Also
> + * note that a 64bit value will be treated as an integer. In the same way,
> + * a char is seen as a short.

Are these 'edge' conditions desirable?  If not can we use the compile
time checking tricks to trigger a build failure if they occur?
BUILD_BUG_ON(sizeof(val) == 1) etc.

> + */
> +#define adis_update_bits(adis, reg, mask, val) ({			\
> +	__builtin_choose_expr(sizeof(val) == 8 || sizeof(val) == 4,	\
> +		adis_update_bits_base(adis, reg, mask, val, 4),         \
> +		adis_update_bits_base(adis, reg, mask, val, 2));	\
> +})
> +
> +/**
> + * adis_update_bits() - Wrapper macro for adis_update_bits_base
> + * @adis: The adis device
> + * @reg: The address of the lower of the two registers
> + * @mask: Bitmask to change
> + * @val: Value to be written
> + *
> + * This macro evaluates the sizeof of @val at compile time and calls
> + * adis_update_bits_base() accordingly. Be aware that using MACROS/DEFINES for
> + * @val can lead to undesired behavior if the register to update is 16bit. Also
> + * note that a 64bit value will be treated as an integer. In the same way,
> + * a char is seen as a short.
> + */
> +#define __adis_update_bits(adis, reg, mask, val) ({			\
> +	__builtin_choose_expr(sizeof(val) == 8 || sizeof(val) == 4,	\
> +		__adis_update_bits_base(adis, reg, mask, val, 4),	\
> +		__adis_update_bits_base(adis, reg, mask, val, 2));	\
> +})
> +
>  int adis_enable_irq(struct adis *adis, bool enable);
>  int __adis_check_status(struct adis *adis);
>  int __adis_initial_startup(struct adis *adis);