On Wed, 2016-06-29 at 17:13 +0200, Steffen Trumtrar wrote: > On Wed, May 04, 2016 at 10:55:56AM +0100, Jonathan Cameron wrote: > > > > On 01/05/16 21:02, Jonathan Cameron wrote: > > > > > > On 26/04/16 22:36, Srinivas Pandruvada wrote: > > > > > > > > On Tue, 2016-04-26 at 22:15 +0100, Jonathan Cameron wrote: > > > > > > > > > > > > > > > On 26 April 2016 21:25:22 BST, Srinivas Pandruvada > > > > > <srinivas.pandruva > > > > > da@xxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > > On Mon, 2016-04-25 at 20:31 +0100, Jonathan Cameron wrote: > > > > > > > > > > > > > > > > > > > > > On 21/04/16 11:49, Steffen Trumtrar wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > The filter frequency and sample rate have a fixed > > > > > > > > relationship. > > > > > > > > Only the filter frequency is unique, however. > > > > > > > > Currently the driver ignores the filter settings for 32 > > > > > > > > Hz and > > > > > > > > 64 Hz. > > > > > > > > > > > > > > > > This patch adds the necessary callbacks to be able to > > > > > > > > configure > > > > > > > > and read the filter setting from sysfs. > > > > > > > > > > > > > > > > Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix > > > > > > > > .de> > > > > > > > cc'd Srinivas as it's his driver... Looks superficially > > > > > > > fine to > > > > > > > me. > > > > > > > > > > > > > > Jonathan > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > Changing the sample rate will result in using the first > > > > > > > > match > > > > > > > > and therefore selecting the filter accordingly. Is this > > > > > > > > a > > > > > > > > misuse > > > > > > > > of the ABI and should be handled differently or is this > > > > > > > > okay? > > > > > > > > > > > > > > This is the reason they were omitted. Now you can't > > > > > > uniquely set > > > > > > 100Hz > > > > > > sampling frequency. Depending on filter it will have > > > > > > different > > > > > > results. > > > > > > > > > > > > I think this needs some ABI level changes, where you > > > > > > display > > > > > > available > > > > > > and allow to specify both ODR and Filter to uniquely > > > > > > select. > > > > > Unfortunately the moment the ABI allows for combined elements > > > > > it > > > > > becomes a > > > > > nightmare for complexity. In some devices a single parameter > > > > > change > > > > > can > > > > > change everything else. There are no simple rules > > > > > unfortunately. > > > > > > > > > > The way we avoid this being a problem is that we very > > > > > deliberately > > > > > allow any ABI element > > > > > to be able to result in a change in any other. This includes > > > > > changing the > > > > > available values list as here. It might be slightly nicer to > > > > > jump to > > > > > the nearest > > > > > available option though. > > > > > > > > > > An alternative would be to have an interface to fake such > > > > > changes > > > > > then > > > > > apply them atomically if possible. > > > > > That level of complexity just does seem warranted here and > > > > > would > > > > > still need userspace to check valid ranges as it > > > > > pretends to change the state. Hence no real gain.... > > > > > > > > > I think we should add some documentation for this driver about > > > > this. > > > > They should rather change filer rather than sampling freq to > > > > have > > > > unique setting. > > > whilst that would get around the problem, people are going to be > > > expecting > > > to have explicit control of sampling frequency if they see it is > > > variable for > > > the part... > > > > > > Tricky unfortunately. > > So Srinivas, I'm in favour of the patch as it stands. Have I > > convinced you? > So, any conclusion ? :-) Sorry, I missed this. I am fine with this change. Thanks, Srinivas > > Best regards, > Steffen > -- 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
