linux-kernel - Re: [PATCH v2 0/4] iio: light: fix scale in veml6030

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Message-Id: <D7BFFUH97D61.25C1T8JHA8WES@gmail.com>
Date: Sat, 25 Jan 2025 21:12:57 +0100
From: "Javier Carrasco" <javier.carrasco.cruz@...il.com>
To: "Jonathan Cameron" <jic23@...nel.org>
Cc: "Lars-Peter Clausen" <lars@...afoo.de>, "Rishi Gupta"
 <gupt21@...il.com>, "Matti Vaittinen" <mazziesaccount@...il.com>,
 <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Jonathan
 Cameron" <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v2 0/4] iio: light: fix scale in veml6030

On Sat Jan 25, 2025 at 1:33 PM CET, Jonathan Cameron wrote:
> On Sun, 19 Jan 2025 18:31:57 +0100
> Javier Carrasco <javier.carrasco.cruz@...il.com> wrote:
>
> > 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. In order to ease the
> >   calculations, iio_gts_get_total_gain() has been exported to avoid
> >   working directly with the scale in NANO, that would require 64-bit
> >   operations.
> >
> > To ease the usage of the iio-gts selectors, patches 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>
> Whilst we might consider a backport eventually.  This is a huge patch
> to do that with.  Hence I'll take this the slow way for next merge window.
>
> For now I've applied patches 1 and 2 in the interest of nibbling away
> at what we will need to see again ;)
>
> Jonathan
>

Thanks, Jonathan.

Could you please tell me where you applied them, so I
can rebase onto that branch? I did not find them in linux-next/master,
iio/testing or iio/togreg. Or should they show up in one of those
within the next hours/days?

Best regards,
Javier Carrasco.