linux-kernel - Re: [PATCH v2] iio: adc: adi-axi-adc: fix ad7606_bus_reg

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Message-ID: <20250531171837.1490051a@jic23-huawei>
Date: Sat, 31 May 2025 17:18:37 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Michael Hennerich <Michael.Hennerich@...log.com>, Angelo Dureghello
 <adureghello@...libre.com>, Guillaume Stols <gstols@...libre.com>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: adi-axi-adc: fix ad7606_bus_reg_read()

On Fri, 30 May 2025 16:50:14 -0500
David Lechner <dlechner@...libre.com> wrote:

> Mask the value read before returning it. The value read over the
> parallel bus via the AXI ADC IP block contains both the address and
> the data, but callers expect val to only contain the data.
> 
> axi_adc_raw_write() takes a u32 parameter, so addr was the wrong type.
> This wasn't causing any issues but is corrected anyway since we are
> touching the same line to add a new variable.
> 
> Cc: stable@...r.kernel.org
> Fixes: 79c47485e438 ("iio: adc: adi-axi-adc: add support for AD7606 register writing")
> Signed-off-by: David Lechner <dlechner@...libre.com>
I've applied this to my temporary fixes-togreg-for-6.16 branch for now.
That will get rebased on rc1 once available.  As such I'm fine adding
tags or indeed dropping it again if others have feedback!

Jonathan

> ---
> Changes in v2:
> - Use ADI_AXI_REG_VALUE_MASK instead of hard-coding 0xFF.
> - Introduce local variable and use FIELD_PREP() instead of modifying val.
> - Link to v1: https://lore.kernel.org/r/20250530-iio-adc-adi-axi-adc-fix-ad7606_bus_reg_read-v1-1-ce8f7cb4d663@baylibre.com
> ---
>  drivers/iio/adc/adi-axi-adc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index cf942c043457ccea49207c3900153ee371b3774f..fc745297bcb82cf2cf7f30c7fcf9bba2d861a48c 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -445,7 +445,7 @@ static int axi_adc_raw_read(struct iio_backend *back, u32 *val)
>  static int ad7606_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val)
>  {
>  	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> -	int addr;
> +	u32 addr, reg_val;
>  
>  	guard(mutex)(&st->lock);
>  
> @@ -455,7 +455,9 @@ static int ad7606_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val)
>  	 */
>  	addr = FIELD_PREP(ADI_AXI_REG_ADDRESS_MASK, reg) | ADI_AXI_REG_READ_BIT;
>  	axi_adc_raw_write(back, addr);
> -	axi_adc_raw_read(back, val);
> +	axi_adc_raw_read(back, &reg_val);
> +
> +	*val = FIELD_GET(ADI_AXI_REG_VALUE_MASK, reg_val);
>  
>  	/* Write 0x0 on the bus to get back to ADC mode */
>  	axi_adc_raw_write(back, 0);
> 
> ---
> base-commit: 7cdfbc0113d087348b8e65dd79276d0f57b89a10
> change-id: 20250530-iio-adc-adi-axi-adc-fix-ad7606_bus_reg_read-f2bbb503db8b
> 
> Best regards,