Re: [RFC] hw/registerfields: add `FIELDx_1CLEAR()` macro

[Richard Henderson]

On 9/1/22 02:02, Wilfred Mallawa wrote:
> From: Wilfred Mallawa <wilfred.mallawa@wdc.com>
>
> Adds a helper macro that implements the `rw1c`
> behaviour.
>
> Ex:
>    uint32_t data = FIELD32_1CLEAR(val, REG, FIELD);
>
> if the specified `FIELD` is set (single/multi bit all fields)
> then the respective field is cleared and returned to `data`.
>
> If ALL bits of the bitfield are not set, then no change and
> val is returned.
>
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>

Why do these operations need to go into hw/registerfields.h?
It's not a common operation, since we've never needed it so far.



r~

> ---
>   include/hw/registerfields.h | 28 ++++++++++++++++++++++++++++
>   1 file changed, 28 insertions(+)
>
> diff --git a/include/hw/registerfields.h b/include/hw/registerfields.h
> index 1330ca77de..5a804f72e3 100644
> --- a/include/hw/registerfields.h
> +++ b/include/hw/registerfields.h
> @@ -115,6 +115,34 @@
>                     R_ ## reg ## _ ## field ## _LENGTH, _v.v);              \
>       _d; })
>   
> +/* Get the max value (uint) discribed by `num_bits` bits */
> +#define MAX_N_BITS(num_bits) ((1 << (num_bits)) - 1)
> +
> +/*
> + * Clear the specified field in reg_val if
> + * all field bits are set, else no changes made. Implements
> + * single/multi-bit `rw1c`
> + */
> +#define FIELD8_1CLEAR(reg_val, reg, field)                                \
> +    ((FIELD_EX8(reg_val, reg, field) ==                                   \
> +      MAX_N_BITS(R_ ## reg ## _ ## field ## _LENGTH)) ?                   \
> +      FIELD_DP8(reg_val, reg, field, 0x00) : reg_val)
> +
> +#define FIELD16_1CLEAR(reg_val, reg, field)                               \
> +    ((FIELD_EX16(reg_val, reg, field) ==                                  \
> +      MAX_N_BITS(R_ ## reg ## _ ## field ## _LENGTH)) ?                   \
> +      FIELD_DP16(reg_val, reg, field, 0x00) : reg_val)
> +
> +#define FIELD32_1CLEAR(reg_val, reg, field)                               \
> +    ((FIELD_EX32(reg_val, reg, field) ==                                  \
> +      MAX_N_BITS(R_ ## reg ## _ ## field ## _LENGTH)) ?                   \
> +      FIELD_DP32(reg_val, reg, field, 0x00) : reg_val)
> +
> +#define FIELD64_1CLEAR(reg_val, reg, field)                               \
> +    ((FIELD_EX64(reg_val, reg, field) ==                                  \
> +      MAX_N_BITS(R_ ## reg ## _ ## field ## _LENGTH)) ?                   \
> +      FIELD_DP64(reg_val, reg, field, 0x00) : reg_val)
> +
>   #define FIELD_SDP8(storage, reg, field, val) ({                           \
>       struct {                                                              \
>           signed int v:R_ ## reg ## _ ## field ## _LENGTH;                  \