linux-kernel - Re: [PATCH v3 2/2] iio: pressure: add Honeywell ABP2 driver

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Message-ID: <aTUlnJTuZwvoSUPh@sunspire.home.arpa>
Date: Sun, 7 Dec 2025 08:58:36 +0200
From: Petre Rodan <petre.rodan@...dimension.ro>
To: Jonathan Cameron <jic23@...nel.org>
Cc: David Lechner <dlechner@...libre.com>, Nuno S?? <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] iio: pressure: add Honeywell ABP2 driver


Hello Jonathan,

thank you for the review.

I actually heard about structs who's elements are 64byte padded so they don't end up in the same cache update in another context but up until today I did not make the connection with what is going on here.
thank you for the detailed explanation.

On Sat, Dec 06, 2025 at 08:54:07PM +0000, Jonathan Cameron wrote:
> On Thu, 04 Dec 2025 17:12:56 +0200
> Petre Rodan <petre.rodan@...dimension.ro> wrote:
> 
> > Adds driver for digital Honeywell ABP2 series of board mount
> > pressure and temperature sensors.

[..]

> Nice clean driver.

well, thank you. I will be sending in a few modifications to my other Honeywell
drivers based on feedback received here.

> > +#include <linux/jiffies.h>
> 
> I'm not immediately spotting use of this but I might well be missing it!

it's an indirect include for the definition of 'HZ'. requested by Andy.

> > +	data->scan.chan[0] = get_unaligned_be24(&data->rx_buf[1]);
> > +	data->scan.chan[1] = get_unaligned_be24(&data->rx_buf[4]);
> Turn on just the second channel and run the test in tools/iio/ for buffered
> reads.
> 
> You'll see data from the first channel not the one userspace asked for.
> Set available_scan_masks = { 0x3, 0 };
> allows the IIO core to know this is what is happening and shuffle the
> data as necessary for you.

nice catch. it was outputing pure garbage (not the first channel) but your change
fixed it.

best regards,
peter

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