On 13/05/15 08:28, Lars-Peter Clausen wrote: > On 05/12/2015 09:06 PM, Jonathan Cameron wrote: >> On 12/05/15 17:56, Lars-Peter Clausen wrote: >>> On 05/08/2015 05:11 PM, Jonathan Cameron wrote: >>>> On 16/04/15 05:01, Robert Dolca wrote: >>>>> This patch adds a new function called iio_trigger_register_with_dev >>>>> which is a wrapper for iio_trigger_register. Besides the iio_trigger >>>>> struct this function requires iio_dev struct. It adds the trigger in >>>>> the device's trigger list and saves a reference to the device in the >>>>> trigger's struct. >>>>> >>>>> When the device is registered, in the trigger folder of the device >>>>> (where current_trigger file resides) a symlink is being created for >>>>> each trigger that was registered width iio_trigger_register_with_dev. >>>>> >>>>> # ls -l /sys/bus/iio/devices/iio:device0/trigger/ >>>>> total 0 >>>>> -rw-r--r-- 1 root root 4096 Apr 16 08:33 current_trigger >>>>> lrwxrwxrwx 1 root root 0 Apr 16 08:33 trigger0 -> ../../trigg >>>>> er0 >>>>> >>>>> This should be used for device specific triggers. Doing this the user space >>>>> applications can figure out what if the trigger registered by a specific device >>>>> and what should they write in the current_trigger file. Currently some >>>>> applications rely on the trigger name and this does not always work. >>>>> >>>>> This implementation assumes that the trigger is registered before the device is >>>>> registered. If the order is not this the symlink will not be created but >>>>> everything else will work as before. >>>>> >>>>> Signed-off-by: Robert Dolca <robert.dolca@xxxxxxxxx> >>>> I was rather hoping we'd get a few more comments on this. >>>> In principle I like the idea, but it's new ABI and does make life >>>> a tiny bit more complex, so what do people think? >>>> >>>> Few trivial code comments inline. >>> >>> I don't think it adds more information. Both the trigger and the >>> device get registered for the same parent device, so you can already >>> easily find the trigger for a device by going to the parent device >>> and taking a look at the triggers registered by the parent device. >> I had the same thought. The question is whether the slightly gain in >> simplicity for userspace is worth it... I'm undecided at the moment. > > As you may have guessed by now I'm always quite conservative when it > comes to introducing new ABI. Simply because we have to maintain it > forever, the less stuff to maintain forever the better. > > Hence I think all new ABI needs a compelling reason, e.g. like a > improvement in performance. And of course this patch slightly > simplifies things, but in my opinion not enough to justify a ABI > extension. We can always find ways to simplify the interface, but the > metric for ABI should be whether the simplification actually matters. > In this case I don't think it does, finding the trigger for a device > is not really hot-path. The amount of time saved will be disappear in > the noise. > > And in my opinion applications shouldn't directly use the low-level > ABI but rather use middle-ware libraries/frameworks, like e.g. > libiio, and that's where you'd hide the complexities of a operation. > > - Lars I'll go with Lars response on this one. Not worth the hassle. That's the nature of an RFC of course! Jonathan > > -- > 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 -- 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
