On Tue, 2015-09-15 at 12:03 +0100, Mark Rutland wrote: > On Tue, Sep 15, 2015 at 11:46:02AM +0100, Jon Medhurst (Tixy) wrote: > > On Tue, 2015-09-15 at 10:37 +0100, Punit Agrawal wrote: > > > "Jon Medhurst (Tixy)" <tixy@xxxxxxxxxx> writes: > > > > > > > On Mon, 2015-09-14 at 15:38 +0100, Punit Agrawal wrote: > > > >> Mark Rutland <mark.rutland@xxxxxxx> writes: > > > >> > > [...] > > > >> The way the SCP interface is defined, the sensor identifiers are > > > >> contiguous, > > > > > > > > Is there any documentation other than DUI0922A? [1] From what I can seen > > > > that just says it's a 16-bit value and doesn't put any particular > > > > constraints on its value. > > > > > > Although not explicitly stated, if you look at the Get Sensor Capability > > > [2] and Get Sensor Info [3] commands you can indirectly infer that the > > > Sensor IDs are contiguous. > > > > I personally wouldn't even indirectly infer they are contiguous from > > what the document says. If I were implementing the firmware I would feel > > quite in my rights to, for example, use the top 8 bits of the ID for a > > sensor type and the bottom 8 for an index, if that made dispatching of > > requests more efficient. Or if some optional hardware was detected as > > missing, leaving some holes in ID space. > > > > As a specification of a 'standard' the document seems to be rather > > lacking. So, Sensor ID should be documented as being "an unsigned > > integer less than then number of sensors returned by the Get Sensor > > Capability command", or something like that. I guess clocks and other > > devices suffer from similar lack of specificity. > > I think from the PoV of the binding, this doesn't matter. The value is > just an arbitrary opaue token written down in a spec, that the FW > understands how to interpret. True, it's the Linux implementation in following patches that has assumptions, e.g. for loops iterating over id's 0..N-1 > > I only asked about how the IDs were organised because I thought there > was additional translation in the kernel, but this is not the case. > > The only potential problem is bit-width. Punit, I assume the value is > 32-bit (or less) in the messages to the FW? It's 16 bit. -- Tixy -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
