linux-kernel - [PATCH 0/2] iio: light: fix scale in veml6030

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Message-Id: <20250107-veml6030-scale-v1-0-1281e3ad012c@gmail.com>
Date: Tue, 07 Jan 2025 21:50:20 +0100
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, Rishi Gupta <gupt21@...il.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: [PATCH 0/2] iio: light: fix scale in veml6030

This series follows a similar approach as recently used for the veml3235
by using iio-gts to manage the scale as stated in the ABI. In its
current form, the driver exposes the hardware gain instead of the
multiplier for the raw value to obtain a value in lux.

Although this driver and the veml3235 have many similarities, there are
two main differences in this series compared to the one used to fix the
other driver:

- The veml6030 has fractional gains, which are not supported by the
  iio-gts helpers. My first attempt was adding support for them, but
  that made the whole iio-gts implementation more complex, cumbersome,
  and the risk of affecting existing clients was not negligible.
  Instead, a x8 factor has been used for the hardware gain to present
  the minimum value (x0.125) as x1, keeping linearity. The scales
  iio-gts generates are therefore right without any extra conversion,
  and they match the values provided in the different datasheets.

- This driver included a processed value for the ambient light, maybe
  because the scale did not follow the ABI and the conversion was not
  direct. To avoid breaking userspace, the functionality has been kept,
  but of course using the fixed scales. That requires using intermediate
  u64 values u64 divisions via div_u64() and do_div() to avoid overflows.

To ease the usage of the iio-gts selectors, a previous patch to support
regfields and caching has been included.

This issue has been present since the original implementation, and it
affects all devices it supports.

This series has been tested with a veml7700 (same gains as veml6030) and
a veml6035 with positive results.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
---
Javier Carrasco (2):
      iio: light: veml6030: extend regmap to support regfields and caching
      iio: light: veml6030: fix scale to conform to ABI

 drivers/iio/light/Kconfig    |   1 +
 drivers/iio/light/veml6030.c | 594 ++++++++++++++++++++-----------------------
 2 files changed, 282 insertions(+), 313 deletions(-)
---
base-commit: 577a66e2e634f712384c57a98f504c44ea4b47da
change-id: 20241231-veml6030-scale-8142f387e7e6

Best regards,
-- 
Javier Carrasco <javier.carrasco.cruz@...il.com>