On 04/12/2011 05:21 PM, Mark Brown wrote: > On Tue, Apr 12, 2011 at 12:08:22PM +0100, Hennerich, Michael wrote: > > Please fix your mail client to word wrap at less than 80 columns - see > Documentation/email-clients.txt for suggestions. I've reflowed your > text for legibility. > > >> I wonder why the voltage and current regulator framework doesn't >> support negative voltages. We like to use the framework to specify >> bipolar reference voltages used with converters. However in various >> places negative voltages are treated as error codes, thus causing the >> regulator to exit on probe. >> > Basically just a lack of demand - there are few negative supplies in > the mobile systems that were looked at, and most of those are like the > charge pumps found in audio CODECs and not really visible as regulators > that could be used with other devices. > Hi Mark, Contrast control for LC Displays typically use negative voltages, too I agree that demand for this on typical mobile devices is low, however we like to use the regulator framework in the IIO subsystem where negative voltages are quite common. > >> As a workaround someone could say we specify positive and negative >> supply by label with absolute values and add the negative sign in the >> consumer driver. However that doesn't work well, since the bipolar >> 'negative' supply may also occasionally be positive. >> > That'd probably work. Or update the API to allow negative voltages to > be returned more easily; off the top of my head the only real issue is > get_voltage() and so on. It'd not be great for usability, though. > Updating the core to allow negative and zero voltages, is not straight forward. There are more issues with constrain checking and I currently can't oversee all side effects. I think we need to introduce a new constrains flag (maybe add to valid_modes_mask?), indicating a bipolar regulator. This flag is then used to keep the current implementation untouched for unipolar positive regulators. Thoughts? -- Greetings, Michael -- Analog Devices GmbH Wilhelm-Wagenfeld-Str. 6 80807 Muenchen Sitz der Gesellschaft: Muenchen; Registergericht: Muenchen HRB 40368; Geschaeftsfuehrer:Dr.Carsten Suckrow, Thomas Wessel, William A. Martin, Margaret Seif -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
