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Date:   Thu, 20 Apr 2023 06:47:32 -0700
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Subject: Re: [PATCH 2/3] iio: potentiometer: Add support for the Renesas X9250
 potentiometers
Content-Language: en-US
To:     Herve Codina <herve.codina@bootlin.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
References: <20230420121320.252884-1-herve.codina@bootlin.com>
 <20230420121320.252884-3-herve.codina@bootlin.com>
From:   Lars-Peter Clausen <lars@metafoo.de>
In-Reply-To: <20230420121320.252884-3-herve.codina@bootlin.com>
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Precedence: bulk

On 4/20/23 05:13, Herve Codina wrote:
> The Renesas X9250 integrates four digitally controlled potentiometers.
> On each potentiometer, the X9250T has a 100 kOhms total resistance and
> the X9250U has a 50 kOhms total resistance.
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Hi,

Looks perfect! Just one small comment.

> +static int x9250_write8(struct x9250 *x9250, u8 cmd, u8 val)
> +{
> +	struct spi_transfer xfer = {
> +		.tx_buf = &x9250->spi_tx_buf,
> +		.len = 3,
> +	};
> +	int ret;
> +
> +	BUILD_BUG_ON(sizeof(x9250->spi_tx_buf) < 3);
> +
> +	mutex_lock(&x9250->lock);
> +
> +	x9250->spi_tx_buf[0] = 0x50;
The 0x50 shows up as a magic constant in multiple places, a define for 
it would be nice.
> +	x9250->spi_tx_buf[1] = cmd;
> +	x9250->spi_tx_buf[2] = val;
> +
> +	ret = spi_sync_transfer(x9250->spi, &xfer, 1);
> +
> +	mutex_unlock(&x9250->lock);
> +
> +	return ret;
> +}