linux-kernel - Re: [PATCH v2 1/6] iio: adc: ad4080: fix chip identification

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Message-ID: <3c959b42a01d3af75fdf536fc3e3289a076953c3.camel@gmail.com>
Date: Tue, 30 Sep 2025 13:35:46 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>, jic23@...nel.org, 
	robh@...nel.org, conor+dt@...nel.org, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/6] iio: adc: ad4080: fix chip identification

Hi Antoniu,

I think that for a series like this you should include a cover letter...

On Tue, 2025-09-30 at 10:32 +0000, Antoniu Miclaus wrote:
> Fix AD4080 chip identification by using the correct 16-bit product ID
> (0x0050) instead of GENMASK(2, 0). Update the chip reading logic to
> use regmap_bulk_read to read both PRODUCT_ID_L and PRODUCT_ID_H
> registers and combine them into a 16-bit value.
> 
> The original implementation was incorrectly reading only 3 bits,
> which would not correctly identify the AD4080 chip.
> 
> Fixes: 6b31ba1811b6 ("iio: adc: ad4080: add driver support")
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
> changes in v2:
>  - add the chip id handling into a separate commit.
>  - use regmap_bulk_read.
>  drivers/iio/adc/ad4080.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad4080.c b/drivers/iio/adc/ad4080.c
> index 6e61787ed321..b80560aebe2d 100644
> --- a/drivers/iio/adc/ad4080.c
> +++ b/drivers/iio/adc/ad4080.c
> @@ -125,7 +125,7 @@
>  
>  /* Miscellaneous Definitions */
>  #define
> AD4080_SPI_READ						BIT(7)
> -#define AD4080_CHIP_ID						GENMASK(2, 0)
> +#define AD4080_CHIP_ID						0x0050
>  
>  #define AD4080_LVDS_CNV_CLK_CNT_MAX				7
>  
> @@ -458,10 +458,11 @@ static int ad4080_setup(struct iio_dev *indio_dev)
>  	if (ret)
>  		return ret;
>  
> -	ret = regmap_read(st->regmap, AD4080_REG_CHIP_TYPE, &id);
> +	ret = regmap_bulk_read(st->regmap, AD4080_REG_PRODUCT_ID_L, &id, 2);
>  	if (ret)
>  		return ret;
>  
> +	id = get_unaligned_le16(&id);

Being id an 'unsigned int' I'm not really sure the above will work on big endian
machines as we should only populate the 2 MSB, right? But independent of that,
id is only being used in here so I would use proper __le16 (and u16) and
le16_to_cpu().

- Nuno Sá

>  	if (id != AD4080_CHIP_ID)
>  		dev_info(dev, "Unrecognized CHIP_ID 0x%X\n", id);
>