linux-kernel - Re: [PATCH v1 6/8] iio: dac: ds4424: clear outputs on probe

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Message-ID: <aXNGhVTuzJpzQkxV@pengutronix.de>
Date: Fri, 23 Jan 2026 10:59:33 +0100
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.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 v1 6/8] iio: dac: ds4424: clear outputs on probe

On Fri, Jan 23, 2026 at 09:38:04AM +0000, Jonathan Cameron wrote:
> On Mon, 19 Jan 2026 19:24:22 +0100
> Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> 
> > The DS44xx devices have no reset pin or reset bit, so output registers
> > may retain preconfigured values across reboot or warm reset.
> > 
> > Also, the driver suspend/resume path restores from data->raw. When the
> > device is first probed, data->raw is zero-initialized and may not match
> > the actual hardware state. A later suspend/resume can therefore change an
> > output from a preconfigured non-zero value to 0 mA.
> 
> For DACs we often want to retain settings from before kernel load (or
> on exit of the driver).  Can we just read them back from the device to
> fill in the cached versions?  If we can I think that would be preferred
> option.

ACK, i was not sure what is the best way here.

Best Regards,
Oleksij
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