Re: [PATCH] drivers/iio/accel/kxcjk-1013: Retrieve mount-matrix from ACPI Implement kxj_acpi_orientation to retrieve mount matrix from ACPI ROTM method

[Jonathan Cameron <jic23@kernel.org>]

On Thu,  8 Feb 2024 21:03:26 +0000
Sean Rhodes <sean@starlabs.systems> wrote:

> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Sean Rhodes <sean@starlabs.systems>

Hi Sean.

Please make sure to match local style for patch titles.
Something along the lines of:

iio: accel: kxcjk-1013: Implement ACPI method ROTM to retrieve mount matrix.

A few minor things inline. Otherwise this looks fine.
At somepoint it might be nice to factor out a library for this call
as it seems to be reasonably common (I think it's a windows thing as it's not
standard ACPI spec stuff).  *mutters darkly that they should at least have
reserved the ID rather than making it up*

Jonathan


> ---
>  drivers/iio/accel/kxcjk-1013.c | 86 ++++++++++++++++++++++++++++++++--
>  1 file changed, 83 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/accel/kxcjk-1013.c b/drivers/iio/accel/kxcjk-1013.c
> index 894709286b0c..f5ac06d5566c 100644
> --- a/drivers/iio/accel/kxcjk-1013.c
> +++ b/drivers/iio/accel/kxcjk-1013.c
> @@ -619,6 +619,83 @@ static int kxcjk1013_set_power_state(struct kxcjk1013_data *data, bool on)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_ACPI
> +static bool kxj_acpi_orientation(struct device *dev,
> +				 struct iio_mount_matrix *orientation)
> +{
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	struct acpi_device *adev = ACPI_COMPANION(dev);
> +	char *str;
> +	union acpi_object *obj, *elements;
> +	acpi_status status;
> +	int i, j, val[3];
> +	bool ret = false;
> +
> +	if (!acpi_has_method(adev->handle, "ROTM")) {
> +		return false;
> +	}
Kernel style is only use brackets for multiple line statements.
	if (!..)
		return false;

> +
> +	status = acpi_evaluate_object(adev->handle, "ROTM", NULL, &buffer);
> +	if (ACPI_FAILURE(status)) {
> +		dev_err(dev, "Failed to get ACPI mount matrix: %d\n", status);
> +		goto out;
It would be unusual if this has as side effect on error of leaving the buffer
allocated. Looking at the code there might be a path, if the copy fails,
acpi_ut_copy_iobject_to_eobject() but I think that can't actually fail because
we've already checked the source object is valid when querying it's size etc.

Other cases (I checked a couple only ) we have in tree assume that we don't need to free the buffer
if we fail this call.

> +	}
> +
> +	obj = buffer.pointer;
> +	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 3) {
> +		dev_err(dev, "Unknown ACPI mount matrix package format\n");
> +		goto out;
> +	}
> +
> +	elements = obj->package.elements;
> +	for (i = 0; i < 3; i++) {
> +		if (elements[i].type != ACPI_TYPE_STRING) {
> +			dev_err(dev, "Unknown ACPI mount matrix element format\n");
> +			goto out;
> +		}
> +
> +		str = elements[i].string.pointer;
> +		if (sscanf(str, "%d %d %d", &val[0], &val[1], &val[2]) != 3) {
> +			dev_err(dev, "Incorrect ACPI mount matrix string format\n");
> +			goto out;
> +		}
> +
> +		for (j = 0; j < 3; j++) {
> +			switch (val[j]) {
> +			case -1: str = "-1"; break;
> +			case 0:  str = "0";  break;
> +			case 1:  str = "1";  break;
> +			default: goto unknown_format;

? Where does that go?

> +			}
> +			orientation->rotation[i * 3 + j] = str;
> +		}
> +	}
> +
> +	ret = true;
> +
> +out:
> +	kfree(buffer.pointer);
> +	return ret;
> +}
> +
> +static bool kxj1009_apply_acpi_orientation(struct device *dev,
> +					  struct iio_mount_matrix *orientation)
> +{
> +	struct acpi_device *adev = ACPI_COMPANION(dev);
> +
> +	if (adev && acpi_dev_hid_uid_match(adev, "KIOX000A", NULL))
> +		return kxj_acpi_orientation(dev, orientation);
> +
> +	return false;
> +}
> +#else
> +static bool kxj1009_apply_acpi_orientation(struct device *dev,
> +					  struct iio_mount_matrix *orientation)
> +{
> +	return false;
> +}
> +#endif
> +
>  static int kxcjk1013_chip_update_thresholds(struct kxcjk1013_data *data)
>  {
>  	int ret;
> @@ -1449,9 +1526,12 @@ static int kxcjk1013_probe(struct i2c_client *client)
>  	} else {
>  		data->active_high_intr = true; /* default polarity */
>  
> -		ret = iio_read_mount_matrix(&client->dev, &data->orientation);
> -		if (ret)
> -			return ret;
> +		if (!kxj1009_apply_acpi_orientation(&client->dev, &data->orientation)) {
> +			ret = iio_read_mount_matrix(&client->dev, &data->orientation);
> +			if (ret)
> +				return ret;
> +		}
> +
>  	}
>  
>  	ret = devm_regulator_bulk_get_enable(&client->dev,