Re: [PATCH v1 1/2] spi: Add spi_bpw_to_bytes() helper and use it

[Mukesh Kumar Savaliya]

On 4/16/2025 11:46 AM, Andy Shevchenko wrote:
> This helper converts the given bits per word to bytes. The result
> will always be power-of-two (e.g. for 37 bits it returns 8 bytes)
> or 0 for 0 input.
>
> There are a couple of cases in SPI that are using the same approach
> and at least one more (in IIO) would benefit of it. Add a helper
> for everyone.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
>   drivers/spi/spi.c       |  2 +-
>   include/linux/spi/spi.h | 15 +++++++++++++++
>   2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index b0e7702951fe..1bc0fdbb1bd7 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -3800,7 +3800,7 @@ int spi_split_transfers_maxwords(struct spi_controller *ctlr,
>   		size_t maxsize;
>   		int ret;
>   
> -		maxsize = maxwords * roundup_pow_of_two(BITS_TO_BYTES(xfer->bits_per_word));
> +		maxsize = maxwords * spi_bpw_to_bytes(xfer->bits_per_word);
>   		if (xfer->len > maxsize) {
>   			ret = __spi_split_transfer_maxsize(ctlr, msg, &xfer,
>   							   maxsize);
> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
> index 834a09bd8ccc..abfc7f5e19e4 100644
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -1340,6 +1340,21 @@ static inline bool spi_is_bpw_supported(struct spi_device *spi, u32 bpw)
>   	return false;
>   }
>   
> +/**
> + * spi_bpw_to_bytes - Covert bits per word to bytes
> + * @bpw: Bits per word
> + *
> + * This function converts the given @bpw to bytes. The result is always
> + * power-of-two (e.g. for 37 bits it returns 8 bytes) or 0 for 0 input.
Would it be good to say in 4 byte aligned /Multiples ?
> + *
> + * Returns:
> + * Bytes for the given @bpw.
Returns: Bytes for the given @bpw.
Good to keep in one line.
> + */> +static inline u32 spi_bpw_to_bytes(u32 bpw)
u8 bpw ?

struct spi_device {
u8 bits_per_word;
}
so arg should be u8.
> +{
> +	return roundup_pow_of_two(BITS_TO_BYTES(bpw));
> +}
> +
>   /**
>    * spi_controller_xfer_timeout - Compute a suitable timeout value
>    * @ctlr: SPI device