linux-kernel - Re: [PATCH v5 03/10] iio: accel: adxl345: measure right-justified

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Message-ID: <20241208133458.4a8428b7@jic23-huawei>
Date: Sun, 8 Dec 2024 13:34:58 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, devicetree@...r.kernel.org,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 eraretuya@...il.com
Subject: Re: [PATCH v5 03/10] iio: accel: adxl345: measure right-justified

On Thu,  5 Dec 2024 17:13:36 +0000
Lothar Rubusch <l.rubusch@...il.com> wrote:

> Make measurements right-justified, since it is the default for the
> driver and sensor. By not setting the ADXL345_DATA_FORMAT_JUSTIFY bit,
> the data becomes right-judstified. This was the original setting, there
> is no reason to change it to left-justified, where right-justified
> simplifies working on the registers.
> 
> Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>

I'm still confused by this one.  Does this change affect the data output
to userspace?  If seems like it definitely should. If it does we have
an ABI regression somewhere. Is it currently broken and wasn't at some
earlier stage, or is this the patch breaking things?

If it worked and currently doesn't send a fix.  If this changes a previously
working ABI then drop this patch.  Alternative being to fix up the scale
handling to incorporate this justification change.

Jonathan

> ---
>  drivers/iio/accel/adxl345_core.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 88df9547bd6..98ff37271f1 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -184,7 +184,6 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
>  	struct iio_dev *indio_dev;
>  	u32 regval;
>  	unsigned int data_format_mask = (ADXL345_DATA_FORMAT_RANGE |
> -					 ADXL345_DATA_FORMAT_JUSTIFY |
>  					 ADXL345_DATA_FORMAT_FULL_RES |
>  					 ADXL345_DATA_FORMAT_SELF_TEST);
>  	int ret;