linux-kernel - Re: [PATCH v3 1/8] iio: dac: ds4424: fix -128 rejection and refactor raw access

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Message-ID: <20260201144226.218a43cb@jic23-huawei>
Date: Sun, 1 Feb 2026 14:42:26 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, stable@...r.kernel.org,
 kernel@...gutronix.de, linux-kernel@...r.kernel.org,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org, Andy Shevchenko
 <andy@...nel.org>, David Lechner <dlechner@...libre.com>, Nuno
 Sá <nuno.sa@...log.com>, David Jander <david@...tonic.nl>
Subject: Re: [PATCH v3 1/8] iio: dac: ds4424: fix -128 rejection and
 refactor raw access

On Sun, 1 Feb 2026 13:40:42 +0100
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> Hi Jonathan,
> 
> On Thu, Jan 29, 2026 at 05:58:19PM +0000, Jonathan Cameron wrote:
> > On Wed, 28 Jan 2026 16:38:17 +0100
> > Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> >   
> > > The DS442x DAC uses sign-magnitude encoding, so -128 cannot be represented.
> > > Previously, passing -128 resulted in a truncated value that programmed 0mA.
> > > 
> > > Fix this by validating the input against the 7-bit magnitude limit.
> > > Additionally, refactor the raw access logic to use symmetrical bitwise
> > > operations, replacing the union structure.
> > > 
> > > Fixes: d632a2bd8ffc ("iio: dac: ds4422/ds4424 dac driver")
> > > Cc: <stable@...r.kernel.org>
> > > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>  
> > Hi Olkesij
> > 
> > This is good stuff but, this fails the test of being the minimal fix
> > suited for a trivial backport.
> > 
> > The right solution here is split it.  Just apply the correct
> > limit in the fix patch, then the refactors in a patch on top of
> > that which most likely won't be backported for stable.  
> 
> The v1 of this patch was implemented according to the fix patch
> requirements:
> https://lore.kernel.org/all/20260119182424.1660601-5-o.rempel@pengutronix.de/
> 
> May be keep v1 as is and rebase v3 as refactoring stage on top of it?
Perfect.

Thanks!

Jonathan

> 
> Best Regards,
> Oleksij