On Thu, 30 Apr 2020 06:52:50 +0000 "Pop, Cristian" <Cristian.Pop@xxxxxxxxxx> wrote: > Hello to all, > > For those who are receiving this email for the second time, it seems > that linux-iio@xxxxxxxxxxxxxxx, doesn't accept HTML format emails, so > this is a plain text version. > > I have been developing a linux kernel drive for a DAC converter, > ad5766 and it supports changing the output span range, from eight > available output ranges during runtime. This is done setting scale > and offset attributes trough a `write_raw` call. When changing the > range during runtime for this chip, a software reset is necessary, > before writing to the span register. Do you think this is acceptable > upstream? Should we make the span ranges selectable at runtime? From > what I heard, it's not always a good idea to do reset of a device at > runtime. There is no fundamental issue with doing resets at runtime - we often have to do this to get out of error conditions etc and it also often happens if we remove and reprobe a device. What I really don't want to see is a userspace reset control. If some other control requires a reset to actually set the value, then fine. I would suggest you want to block that control unless all the dac channels are disabled. Right now it looks like the driver doesn't support power down, but I think the hardware does from a quick glance at the datasheet. Resetting with powered up channels sounds like a bad idea to me. Thanks, Jonathan > > AD5722 software reset in driver before setting a new offset / range: > https://github.com/analogdevicesinc/linux/blob/4c7d019397e696dcaf735c52169a92fcbe5b5b8b/drivers/iio/dac/ad5766.c#L309 > > AD5722 software reset in driver, before setting a new scale / range: > https://github.com/analogdevicesinc/linux/blob/4c7d019397e696dcaf735c52169a92fcbe5b5b8b/drivers/iio/dac/ad5766.c#L357 > > AD5722 datasheet: > https://www.analog.com/media/en/technical-documentation/data-sheets/AD5722_5732_5752.pdf > > Thanks and best regards, > Cristian Pop
