Re: [RFC] iio: amplifiers: New driver for AD8366 Dual-Digital Variable Gain Amplifier
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On 3/22/2012 9:53 AM, Michael Hennerich wrote:
On 03/22/2012 10:10 AM, Jonathan Cameron wrote:On 3/22/2012 8:52 AM, Michael Hennerich wrote:Hmm.. Don't suppose it really matters but we ought to aim for consistencyOn 03/21/2012 08:34 PM, Jonathan Cameron wrote:I'm open for advice. Since I made the amplifier being an OUT type deviceOn 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 goingto be of one particular existing type).2) Have it as an IIO_ALTVOLTAGE channel as you have here and use extendname. Any real reason for picking altvoltage rather than voltage?I chose IIO_ALTVOLTAGE analogous to our DDS/PLL drivers. Some VGAs/PGAs work from DC, but typically VGAs are HF devices.(by review) at least. This particular part is DC through to 600MHz.True enough. Cleanest way to do this that I can think of is to make a treeClearly 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.wide change to add the raw element to the info_mask. We could allow fora zero info_mask value actually being the equivalent of having only a rawchannel. 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).Well - to make the change less invasive - we could use reversed logic add a new info_mask element IIO_CHAN_INFO_NO_RAW=0. We already reserve 0...
I wondered about doing exactly that as well.Less invasive but then we have a rather illogical setup... If we were out of staging then we'd probably go with that hack, but given we still have scope to make wholesale changes, lets do it properly... Almost every channel should have an info_mask set anyway (only exception is processed channels where nothing is controllable) an there
are very very few of them.I'll do this change if we go with it as I have some patches clearling out IIO_CHAN
macro usage once and for all and this is sure as heck going to clash!
That's what I was thinking. Not ideal, but it's still reasonably machine readable and should work fine with in kernel users as well as long as the reader / writer is expectingWhilst here, we clearly need way of destinguishing values in DB from lineargains. Could add a new return type for read_raw callbacks?That should work. ... and the core adds dB to the string?
it (or the boiler plate code is). -- 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