Jonathan Cameron wrote on 2012-05-08: > On 5/7/2012 4:17 PM, Michael Hennerich wrote: >> On 05/07/2012 05:00 PM, Michael Hennerich wrote: >>> On 03/22/2012 10:10 AM, Jonathan Cameron wrote: >>>> On 3/22/2012 8:52 AM, Michael Hennerich wrote: >>>>> On 03/21/2012 08:34 PM, Jonathan Cameron wrote: >>>>>> On 02/22/2012 12:36 PM, michael.hennerich@xxxxxxxxxx wrote: >>>>>>> From: Michael Hennerich<michael.hennerich@xxxxxxxxxx> >>>>>> Sorry for the slow response on this one. Been off sick... >>>>>> >>>>>> Anyhow, I'm still not sure what the right interface for this type >>>>>> of device is. >>>>>> >>>>>> The obvious options are: >>>>>> >>>>>> 1) Make gain an IIO type (doesn't make much sense as gain is only >>>>>> going >>>>>> to be of one particular existing type). >>>>>> 2) Have it as an IIO_ALTVOLTAGE channel as you have here and use >>>>>> extend >>>>>> name. Any real reason for picking altvoltage rather than > voltage? >>>>> I'm open for advice. Since I made the amplifier being an OUT type >>>>> device >>>>> I chose IIO_ALTVOLTAGE analogous to our DDS/PLL drivers. >>>>> Some VGAs/PGAs work from DC, but typically VGAs are HF devices. >>>> Hmm.. Don't suppose it really matters but we ought to aim for >>>> consistency >>>> (by review) at least. This particular part is DC through to > 600MHz. >>>>>> Clearly gain has the same meaning in either case (assuming it's >>>>>> linear). 3) Make a change to core to allow a channel to have >>>>>> elements in info_mask but not actually to have a raw access. Not >>>>>> entirely sure how we will do that cleanly. Also it's not clear >>>>>> whether the gain would be an IN or an OUT channel type! >>>>> Well - having the ability for channels without raw access element >>>>> would be of interest. >>>> True enough. Cleanest way to do this that I can think of is to make >>>> a tree wide change to add the raw element to the info_mask. We could >>>> allow for a zero info_mask value actually being the equivalent of >>>> having only a raw channel. It's invasive but if we agreee it should >>>> be done now is probably the best time to do it (just post merge >>>> window etc). >>> Hi Jonathan, >>> >>> Thanks for getting this in place. >>> >>>> >>>> Whilst here, we clearly need way of destinguishing values in DB from >>>> linear gains. Could add a new return type for read_raw callbacks? >>> >>> Does something like this work for you? >>> Also wondering if we should introduce IIO_CHAN_INFO_GAIN >>> for amplifier type devices? >> >> Thinking about it a bit more - why not have iio_chan_type:IIO_GAIN? > Lack of consistency with other devices. If we have a pga on the front > of an adc then the type is voltage and control is done via relevant info > element. How is this any different? Well there can be several types of amplifiers voltage, current or none-electronic such as optical amplifiers. The key element GAIN of an amplifier is only the ratio between input and output. The unit cancels out, so why bother with voltage or current? That's why I proposed IIO_GAIN. Anyways I'm fine with IIO_VOLTAGE for now, but I would like to use IIO_CHAN_INFO_GAIN and not IIO_CHAN_INFO_SCALE? 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
