linux-kernel - Re: [PATCH 4/4] iio: dac: mcp4922: add support for mcp48xx series chips

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Date:   Wed, 5 Apr 2023 07:18:46 -0700
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Nicolas Frattaroli <frattaroli.nicolas@...il.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] iio: dac: mcp4922: add support for mcp48xx series
 chips

Hi,

Looks very good. A few small comments inline.
[...]
> @@ -50,6 +58,35 @@ struct mcp4922_state {
>   	},						\
>   }
>   
> +static bool mcp4922_needs_vref(int device_id)

`enum mcp4922_supported_device_ids` instead of `int`. Same for num_channels() below.

> +{
> +	switch (device_id) {
> +	case ID_MCP4902:
> +	case ID_MCP4912:
> +	case ID_MCP4921:
> +	case ID_MCP4922:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> [...]
>   static int mcp4922_spi_write(struct mcp4922_state *state, u8 addr, u32 val)
>   {
>   	state->mosi[1] = val & 0xff;
> @@ -108,11 +145,17 @@ static int mcp4922_write_raw(struct iio_dev *indio_dev,
>   	}
>   }
>   
> -static const struct iio_chan_spec mcp4922_channels[4][MCP4922_NUM_CHANNELS] = {
> +static const struct iio_chan_spec mcp4922_channels[10][MCP4922_NUM_CHANNELS] = {

mcp4922_channels[][MCP4922_NUM_CHANNELS]

So it does not have to be changed again when adding additional devices 
in the future.

> [...]
> @@ -197,11 +244,14 @@ static void mcp4922_remove(struct spi_device *spi)
>   {
>   	struct iio_dev *indio_dev = spi_get_drvdata(spi);
>   	struct mcp4922_state *state;
> +	const struct spi_device_id *id = spi_get_device_id(spi);
>   
>   	iio_device_unregister(indio_dev);
>   	state = iio_priv(indio_dev);
>   	regulator_disable(state->vdd_reg);
> -	regulator_disable(state->vref_reg);
> +	if (mcp4922_needs_vref(id->driver_data)) {
Could be `if (state->vref_reg)`, this way you don't need to lookup the 
spi_device_id. But either way is fine.
> +		regulator_disable(state->vref_reg);
> +	}
>   }
>   
> [...]