linux-kernel - Re: [PATCH 2/3] iio: potentiometer: Add support for the Renesas X9250 potentiometers

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Date:   Thu, 20 Apr 2023 06:47:32 -0700
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Herve Codina <herve.codina@...tlin.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/3] iio: potentiometer: Add support for the Renesas X9250
 potentiometers

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@...tlin.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;
> +}