On 28/06/2016 18:38, Cercueil, Paul wrote:
Hi Phil, I think right now libiio doesn't handle shared-by-dir attributes yet, only shared-by-type. Ideally, 'in_sampling_frequency' should appear as a 'sampling_frequency' attribute on all input channels of your module0 device. Regards, Paul Cercueil Le mardi 28 juin 2016 à 16:55 +0800, Phil Reid a écrit :G'day All, Found something interesting. For a new iio driver I have a shared attribute on direction. .info_mask_shared_by_dir = BIT(IIO_CHAN_INFO_SAMP_FREQ) Which results in sysfs attribute name of: in_sampling_frequency Which results in iio_info giving the following output: iio:device3: module0 7 channels found:
*snip*
sampling: (input) 1 channel-specific attributes found: attr 0: frequency value: 24000 2 device-specific attributes found: attr 0: freq value: 6144000 attr 1: out_en value: 0 Note that the sampling_frequency attr has been converted into an input channel. Modify the definition in industrialio-core.c [IIO_CHAN_INFO_SAMP_FREQ] = "sampling_frequency", to [IIO_CHAN_INFO_SAMP_FREQ] = "samplingfrequency", Results in the following output: iio:device4: module0 6 channels found:
*snip*
3 device-specific attributes found: attr 0: freq value: 6144000 attr 1: in_samplingfrequency value: 24000 attr 2: out_en value: 0 Which makes more sense. So libiio is treating the name sampling as a channel name in 'in_sampling_frequency' assuming that attributes never have an underscore in there name. I'm guessing the same would be the case for out attributes as well. A quick search of the drivers in the kernel to date indicate that IIO_CHAN_INFO_SAMP_FREQ is generally shared by type or all. shared by dir occurs with the iio_simple_dummy, but can't see anything with a real device. I'm using libiio from git://github.com/analogdevicesinc/libiio.git So is this intended, or does libiio need to be smarter on identifying channels and shared attributes? I'm guessing we cant change the kernel interface, which would be the easiest fix. :/
I found making it a info_mask_shared_by_type resulted in the sampling_freq becoming an attribute of all the input channels. I find it a little conintutive that a shared attribute is populated into all the channels. libiio doesn't seem to provide an interface I can find to indicate if a parameter is shared or not. I guess with the current method of multiplexing the data streams it doesn't make sense to have anything other than the same value for sample rate. I just assumed that the sample_frequency would have been a device specific value. -- Regards Phil Reid -- 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
