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

["Sa, Nuno" <Nuno.Sa@analog.com>]

On Tue, 2020-03-03 at 20:48 +0000, Jonathan Cameron wrote:
> 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.

So, I guess there's no arm in the 'edge' conditions if users know what
they are doing :). But I have no problems in making/forcing the right
types by adding the compile time checks...

Will add it in v2

- Nuno Sá
> > + */
> > +#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);