From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4EA57EB6.1020801@metafoo.de> Date: Mon, 24 Oct 2011 17:05:26 +0200 From: Lars-Peter Clausen MIME-Version: 1.0 To: Jonathan Cameron CC: "linux-iio@vger.kernel.org" Subject: Re: Channel-less IIO events References: <4EA56C67.7020203@metafoo.de> <4EA57547.3010804@cam.ac.uk> In-Reply-To: <4EA57547.3010804@cam.ac.uk> Content-Type: text/plain; charset=ISO-8859-1 List-ID: On 10/24/2011 04:25 PM, Jonathan Cameron wrote: > On 10/24/11 14:47, Lars-Peter Clausen wrote: >> Hi, >> >> Some chips generate events which don't really map to a channel, but are >> rather chip global. For example over-temperature events. > That one is a channel. >> Do you think this is something we should add support for or should we rather >> use a dummy channel, which doesn't report any actual values, for propagating >> the event? > Yup, have a temp channel for that one. Conceptually you might have two chips > that are otherwise identical but one has a readable temp channel, the other > doesn't. Userspace that is interested only in events won't care about > this difference. Also we want to report what the conditions are as if it were > a channel we could read. We want to know at what temperature this occurs. Ok, what should a read on such a channel return, an error value or just an dummy value? > [...] >> >> My idea for supporting channel-less events is to add a event_mask to struct >> iio_info, which would be used just like a channels event_mask, but there >> would be no index for the sysfs attributes and for events we would set the >> event number to 0xffff. > Could you give more examples? The temp one to my mind definitely needs a > channel, perhaps others do not? I am not against in principal but not > yet certain exactly when this would make sense... over-temperature is the only one i've seen so far. but other could be under-current or voltage for the whole chip. Thanks - Lars