Messages in this thread | | | Subject | Re: [PATCH RFC] regulator: core: fix handling negative voltages e.g. in EPD PMICs | From | "H. Nikolaus Schaller" <> | Date | Mon, 24 Feb 2020 13:22:21 +0100 |
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> Am 24.02.2020 um 13:05 schrieb Mark Brown <broonie@kernel.org>: > > On Sun, Feb 23, 2020 at 04:35:01PM +0100, Andreas Kemnade wrote: > >> An alternative would be to handle voltages as absolute values. >> There are probably no regulators with support both negative >> and positive output. > > This is what'd be needed, your approach here is a bit of a hack and > leaves some values unrepresentable if they overlap with errnos which > obviously has issues if someone has a need for those values.
Negative ERRNOs have BIT(31) set.
Since voltage integers on a 32 bit architecture represent µV this would still allow voltages up to (2^31 - 1) µV i.e. 2 kV with BIT(31) not set.
Therefore it seems very unlikely that anyone needs to represent voltages above 2 kV within a Linux system through a regulator.
So I'd say any negative return value got regulator_get_voltage() can be treated as an error.
And regulators for negative voltages could be represented by their absolute value (and maybe a _neg component in the regulator name).
But then it seems to be a little inconsistent that the voltage parameters of regulator_set_voltage_unlocked() are signed integers and not unsigned.
So shouldn't that be protected against attempting to set negative voltages?
Just my 2 cts.
BR, Nikolaus
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