linux-kernel - Re: [PATCH v2 1/2] iio: mpl3115: add threshold events support

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Message-ID: <aQhmNDoI8k3KvyMR@smile.fi.intel.com>
Date: Mon, 3 Nov 2025 10:22:12 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Antoni Pokusinski <apokusinski01@...il.com>, dlechner@...libre.com,
	nuno.sa@...log.com, andy@...nel.org, marcelo.schmitt1@...il.com,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] iio: mpl3115: add threshold events support

On Sun, Nov 02, 2025 at 10:38:08AM +0000, Jonathan Cameron wrote:
> On Fri, 31 Oct 2025 21:18:22 +0100
> Antoni Pokusinski <apokusinski01@...il.com> wrote:

...


> Generally looks good to me, but some comments on the 24 bit value reading.

> > +		i2c_smbus_read_i2c_block_data(data->client,
> > +					      MPL3115_OUT_PRESS,
> > +					      3, (u8 *)&val_press);
> 
> This is an oddity.  Why read into a __be32 when it's a 24bit number?
> I guess it doesn't really matter as you just need a big enough space
> and throw the value away.  However, I'd read it into a u8 [3]; then size off that
> as well.
> 
> There are two existing cases of this in the driver. One of them should use
> get_unaligned_be24 on a u8[3] buffer.  The other one is more complex as it's
> reading directly into the scan buffer that gets pushed to the kfifo and is
> reading into a u8 buffer ultimately anyway so at least there is no
> real suggestion of it being 32 bits (just a +4 shift to deal with natural
> alignment as the storage has to be power of 2 in that case.).
> 
> hmm. I think either we should tidy up the easy case (_read_info_raw) +
> use a u8[3] here or just stick to this being odd.
> My preference would be to have another patch tidying up the other case
> + use a u8[3] here.

Just a side question... Wondering, if we actually can defined __be24 and __le24
types (or at least u24) for really explicit cases.

-- 
With Best Regards,
Andy Shevchenko