Re: [PATCH v2] iio: frequency: ad9832: Update bit manipulation macros to use FIELD_PREP and GENMASK
From: Jonathan Cameron
Date: Thu Mar 27 2025 - 11:22:46 EST
On Thu, 27 Mar 2025 01:50:07 +0530
Siddharth Menon <simeddon@xxxxxxxxx> wrote:
> Update AD9832_PHASE and RES_MASK to use FIELD_PREP and GENMASK for
> clean bitmask generation and improved maintainability.
>
> Suggested-by: Marcelo Schmitt <marcelo.schmitt1@xxxxxxxxx>
> Signed-off-by: Siddharth Menon <simeddon@xxxxxxxxx>
Hi Siddharth,
> ---
> The previous patch would not apply cleanly as I was not working on a
> clean branch
> v1->v2:
> Resolve previous patch application issues
>
> drivers/staging/iio/frequency/ad9832.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> index 140ee4f9c137..6e463488462a 100644
> --- a/drivers/staging/iio/frequency/ad9832.c
> +++ b/drivers/staging/iio/frequency/ad9832.c
> @@ -59,7 +59,7 @@
> #define AD9832_CMD_SLEEPRESCLR 0xC
>
> #define AD9832_FREQ BIT(11)
> -#define AD9832_PHASE(x) (((x) & 3) << 9)
> +#define AD9832_PHASE(x) FIELD_PREP(GENMASK(10, 9), x)
This code is mixing two styles, the sort of 'function' to set
case here and the providing of direct masks that
are suitable for inline FIELD_PREP / FIELD_GET.
I'd prefer this was changed to the second style
#define AD9832_PHASE_MASK GENMASK(10, 9)
Then where it used inline you can use the mask directly to clear
the bits + an inline FIELD_PREP() to set them to the desired
value. That's cleaner than current situation where the value 3 is
passed to this macro to generate the mask.
There are other cases in the code where we have the pattern:
if (val)
st->ctrl_ss &= ~AD9832_SELSRC;
else
st->ctrl_ss |= AD9832_SELSRC;
which could be rewritten as:
st->ctrl_ss &= ~AD932_SELSRC;
st->ctrl_ss |= FIELD_PREP(AD932_SELSRC, !!val);
the !! is needed to ensure we get 0, 1. Could also do
val ? 1 : 0 if you prefer.
So overall a good cleanup would be to move to consistent use
of masks (including single bit ones) and FIELD_PREP to write
the values.
Jonathan
> #define AD9832_SYNC BIT(13)
> #define AD9832_SELSRC BIT(12)
> #define AD9832_SLEEP BIT(13)
> @@ -69,7 +69,7 @@
> #define ADD_SHIFT 8
> #define AD9832_FREQ_BITS 32
> #define AD9832_PHASE_BITS 12
> -#define RES_MASK(bits) ((1 << (bits)) - 1)
> +#define RES_MASK(bits) GENMASK((bits) - 1, 0)
>
> /**
> * struct ad9832_state - driver instance specific data