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Date: Thu, 23 Apr 2026 18:59:23 +0100
From: Jonathan Cameron <jic23@kernel.org>
To: Rodrigo Alencar via B4 Relay
 <devnull+rodrigo.alencar.analog.com@kernel.org>
Cc: rodrigo.alencar@analog.com, linux-iio@vger.kernel.org,
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Auchter
 <michael.auchter@ni.com>, linux-hardening@vger.kernel.org, Lars-Peter
 Clausen <lars@metafoo.de>, Michael Hennerich
 <Michael.Hennerich@analog.com>, David Lechner <dlechner@baylibre.com>, Andy
 Shevchenko <andy@kernel.org>, Rob Herring <robh@kernel.org>, Krzysztof
 Kozlowski <krzk+dt@kernel.org>, Conor Dooley <conor+dt@kernel.org>, Kees
 Cook <kees@kernel.org>, "Gustavo A. R. Silva" <gustavoars@kernel.org>,
 Philipp Zabel <p.zabel@pengutronix.de>
Subject: Re: [PATCH 12/22] iio: dac: ad5686: fix powerdown control
Message-ID: <20260423185923.5f25da8d@jic23-huawei>
In-Reply-To: <20260422-ad5313r-iio-support-v1-12-ed7dca001d1b@analog.com>
References: <20260422-ad5313r-iio-support-v1-0-ed7dca001d1b@analog.com>
	<20260422-ad5313r-iio-support-v1-12-ed7dca001d1b@analog.com>
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On Wed, 22 Apr 2026 15:45:46 +0100
Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:

> From: Rodrigo Alencar <rodrigo.alencar@analog.com>
> 
> This patch fixes powerdown control issues by protecting the cached
> powerdown states with mutex access, and by using a proper bit shift for
> the powerdown mask values. During initialization, powerdown bits are
> initialized so that unused bits are set to 1 and the correct bit shift is
> used.
> 

Mostly avoiding repeating stuff Andy raised already.

> Dual-channel devices use one-hot encondig in the address and that reflects

encoding.

> on the position of the powerdown bits, which are not channel-index based
> for that case. Quad-channel devices also use one-hot encondig for the
> channel address but the result of log2(address) coincides with the channel
> index value.
> 
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
>
>  static int ad5686_get_powerdown_mode(struct iio_dev *indio_dev,
>  				     const struct iio_chan_spec *chan)
>  {
>  	struct ad5686_state *st = iio_priv(indio_dev);
> +	int mode, shift = ad5686_pd_mask_shift(chan);
Split that into two lines.  
	int shift = ...
	int mode;

Having a mixture of initialized and not is not good for readability.

>  
> -	return ((st->pwr_down_mode >> (chan->channel * 2)) & 0x3) - 1;
> +	mutex_lock(&st->lock);
> +	mode = ((st->pwr_down_mode >> shift) & 0x3) - 1;
> +	mutex_unlock(&st->lock);
> +
> +	return mode;
...