Re: [PATCH v2 6/8] iio: dac: ds4424: fix -128 rejection and refactor raw access

Oleksij Rempel
2026-01-27T10:49:14Z

On Tue, Jan 27, 2026 at 12:42:24PM +0200, Andy Shevchenko wrote:
> On Tue, Jan 27, 2026 at 07:09:37AM +0100, Oleksij Rempel wrote:
> > The DS442x DAC uses sign-magnitude encoding, so -128 cannot be represented.
> > Previously, passing -128 resulted in a truncated value that programmed 0mA.
> >
> > Fix this by validating the input against the 7-bit magnitude limit.
> > Additionally, refactor the raw access logic to use symmetrical bitwise
> > operations, replacing the union structure.
>
> > Fixes: d632a2bd8ffc ("iio: dac: ds4422/ds4424 dac driver")
> > + /*
> > + * Currents exiting the IC (Source) are positive.
> > + * Canonicalize 0 to sink; datasheet treats sign as don't-care.
> > + */
> > + if (val > 0)
> > + abs_val |= DS4424_DAC_SOURCE;
>
> Hmm... Maybe 0 should be excluded as invalid?

0 is valid value for no current flow (power off). The direction bit
DS4424_DAC_SOURCE will just make no difference if value is 0.

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