On 3/12/23 18:51, Jonathan Cameron wrote:
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.
Are you sure...? I don't like the idea of polluting generated docs with
documentation for this type of tiny internal pieces not usable outside
this component anyways...
+ * 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.
Ever considered a career as a politician? ;) (No offense intended - and
feel free to change your mind on this. I don't expect this to be done
tomorrow)
+++ 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.
Ok. I'll do the move for the next version.
Yours,
-- Matti
Jonathan
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
