Re: [PATCH 6/8] hw/i2c: fix VOUT_MODE representation on little-endian machines

On Thu, 30 Jul 2026 at 00:13, Titus Rwantare <[email protected]> wrote:
>
> From: Jason Fan <[email protected]>
>
> Even though VOUT_MODE is only one byte, bitfields are allocated in the
> order specific to the host's endianness.
>
> Signed-off-by: Titus Rwantare <[email protected]>
> Signed-off-by: Jason Fan <[email protected]>
> ---
>  include/hw/i2c/pmbus_device.h | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/include/hw/i2c/pmbus_device.h b/include/hw/i2c/pmbus_device.h
> index 9f3569e997..03b2c21c19 100644
> --- a/include/hw/i2c/pmbus_device.h
> +++ b/include/hw/i2c/pmbus_device.h
> @@ -449,10 +449,17 @@ typedef struct PMBusCoefficients {
>  /**
>   * VOUT_Mode bit fields
>   */
> +#if HOST_BIG_ENDIAN
>  typedef struct PMBusVoutMode {
>      uint8_t  mode:3;
>      int8_t   exp:5;
>  } PMBusVoutMode;
> +# else
> +typedef struct PMBusVoutMode {
> +    int8_t   exp:5;
> +    uint8_t  mode:3;
> +} PMBusVoutMode;
> +#endif

This is why where possible we don't use C bitfields for guest
data structures. Better to use the FIELD macros from
include/hw/core/registerfields.h.

thanks
-- PMM