On Mon, 6 Mar 2023 14:52:57 +0200 Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > On Mon, Mar 06, 2023 at 11:17:15AM +0200, Matti Vaittinen wrote: > > Some light sensors can adjust both the HW-gain and integration time. > > There are cases where adjusting the integration time has similar impact > > to the scale of the reported values as gain setting has. > > > > IIO users do typically expect to handle scale by a single writable 'scale' > > entry. Driver should then adjust the gain/time accordingly. > > > > It however is difficult for a driver to know whether it should change > > gain or integration time to meet the requested scale. Usually it is > > preferred to have longer integration time which usually improves > > accuracy, but there may be use-cases where long measurement times can be > > an issue. Thus it can be preferable to allow also changing the > > integration time - but mitigate the scale impact by also changing the gain > > underneath. Eg, if integration time change doubles the measured values, > > the driver can reduce the HW-gain to half. > > > > The theory of the computations of gain-time-scale is simple. However, > > some people (undersigned) got that implemented wrong for more than once. > > > > Add some gain-time-scale helpers in order to not dublicate errors in all > > drivers needing these computations. > > ... > > > +/* > > If it's deliberately not a kernel doc, why to bother to have it looking as one? > It's really a provocative to some people who will come with a patches to "fix" > this... Just make it kernel-doc. > > > + * iio_gts_get_gain - Convert scale to total gain > > + * > > + * Internal helper for converting scale to total gain. > > + * > > + * @max: Maximum linearized scale. As an example, when scale is created > > + * in magnitude of NANOs and max scale is 64.1 - The linearized > > + * scale is 64 100 000 000. > > + * @scale: Linearized scale to compte the gain for. > > + * > > + * Return: (floored) gain corresponding to the scale. -EINVAL if scale > > + * is invalid. > > + */ > ... > > > +EXPORT_SYMBOL_NS_GPL(iio_gts_total_gain_to_scale, IIO_GTS_HELPER); > > I would say _HELPER part is too much, but fine with me. Hmm. I think I like the HELPER bit as separates it from being a driver. Of course I might change my mind after a few sleeps. > > +++ b/drivers/iio/light/iio-gts-helper.h > > Is it _only_ for a Light type of sensors? I'd move it up a directory and allow for other users. Jonathan
