I resend a counter driver for the EC at https://patchwork.kernel.org/patch/11479437/ I tried a timestamp only IIO sensor, but this is not allowed, as the timestamp channel is very specific: no extended parameters can be added. I did not add a COUNTER_COUNT_TALLY type, as a newer function COUNTER_COUNT_FUNCTION_INCREASE, fits the counter better. I am still using IIO_COUNT (inspired by the st counter driver) to gather the event in real time on the iio side. Gwendal. On Mon, Nov 11, 2019 at 5:16 PM William Breathitt Gray <vilhelm.gray@xxxxxxxxx> wrote: > > On Mon, Nov 11, 2019 at 11:49:55AM +0000, Jonathan Cameron wrote: > > On Sun, 10 Nov 2019 10:14:08 -0500 > > William Breathitt Gray <vilhelm.gray@xxxxxxxxx> wrote: > > > > > On Tue, Sep 24, 2019 at 04:20:51PM +0200, Fabien Lahoudere wrote: > > > > Hi all, > > > > > > > > After some discussions and investigation, the timestamp is very > > > > important for that sync driver. > > > > Google team uses that timestamp to compare with gyroscope timestamp. > > > > > > > > So the important data is timestamp and counter value is useless. > > > > Just the event of counter increment is important to get a timestamp. > > > > > > > > In that case, my idea was to just use an IIO driver with a single > > > > channel with IIO_TIMESTAMP. We discuss this here and it seems > > > > controversial. > > > > > > > > So my question to Jonathan is if we have a timestamp coming from the EC > > > > itself, can we consider this timestamp as a good IIO driver? > > > > > > > > Any other idea is welcome, however Google team would like to manage > > > > only IIO drivers if possible. > > > > > > > > Thanks > > > > > > Jonathan, > > > > > > Should the the timestamp from the EC be introduced as an IIO driver > > > using IIO_TIMESTAMP? > > > > It is is a rather odd driver but I suppose it would be fine with lots > > of clear docs on why it is how it is... > > > > > > > > Since there is no corresponding EC Counter driver in the baseline right > > > now we don't have a conflict yet. If the EC timestamp is introduced as > > > an IIO driver then we should make any future EC Counter driver mutually > > > exclusive with the IIO driver in order to prevent any memory space > > > conflict. At that point we may deprecate the IIO driver and move the > > > timestamp functionality to the corresponding Counter driver. > > > > That route does become somewhat of a mess so I suspect we'd have to have > > a single driver supporting both userspace interfaces. If you are happy > > that we'd be adding a bit of legacy to support for ever then we can go > > that way. > > Generally I'd prefer all components of a device to be supported, but > if this is as Fabien suggests that due to the nature of this particular > device the counter value is of no interest, then a Counter driver is of > little practical use here. In this particular case, it seems better to > restrict the driver support to just the timestamp functionality that > will be used, rather than introduce extra code to expose values that > will likely be ignored and risk adding code to the kernel that becomes > unmaintained due to lack of exposure or interest. > > William Breathitt Gray > > > > > > > > > That's assuming someone is interested in the Count component enough to > > > implement an EC Counter driver; otherwise, the IIO driver will serve > > > just fine if timestamp is the only data desired from this device. > > > > > > William Breathitt Gray > > > >
