Re: [PATCH v2 6/8] iio: dac: ds4424: fix -128 rejection and refactor raw access
From: Oleksij Rempel <o.rempel@pengutronix.de>
Date: 2026-01-27 10:49:14
Also in:
linux-iio, lkml, stable
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:quoted
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.quoted
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. -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |