linux-kernel - Re: [PATCH v3 1/3] iio: mpl3115: use get_unaligned

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Message-ID: <aQ1MfTu24hhk-dKP@debian-BULLSEYE-live-builder-AMD64>
Date: Thu, 6 Nov 2025 22:33:49 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: Antoni Pokusinski <apokusinski01@...il.com>
Cc: jic23@...nel.org, dlechner@...libre.com, nuno.sa@...log.com,
	andy@...nel.org, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] iio: mpl3115: use get_unaligned_be24 to retrieve
 pressure data

On 11/05, Antoni Pokusinski wrote:
> The pressure measurement result is arranged as 20-bit unsigned value
> residing in three 8-bit registers. Hence, it can be retrieved using
> get_unaligned_be24 and by applying 4-bit shift.
> 
> Signed-off-by: Antoni Pokusinski <apokusinski01@...il.com>
> ---
>  drivers/iio/pressure/mpl3115.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/pressure/mpl3115.c b/drivers/iio/pressure/mpl3115.c
...
>  
> -		*val = be32_to_cpu(tmp) >> chan->scan_type.shift;
> +		*val = get_unaligned_be24(tmp) >> 4;
hmm, now the number of bits shifted is dissociated from the channel characteristics.
We can do
		*val = get_unaligned_be24(tmp) >> (24 - chan->scan_type.realbits);
or maybe
		*val = get_unaligned_be24(tmp) >> (sizeof(tmp) - chan->scan_type.realbits);
but it starts becoming too long IMO. Even longer if `tmp` gets a more meaningful
name. Ah well, any of the three forms should work the same at the end of day so
no strong opinion.

Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@...il.com>

>  		return IIO_VAL_INT;
>  	}
>  	case IIO_TEMP: { /* in 0.0625 celsius / LSB */
> -- 
> 2.25.1
>