"Jon Medhurst (Tixy)" <tixy@xxxxxxxxxx> writes: > 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. True. And without a command to convey the list of valid IDs, the consumer of the API would have to iterate over the entire 16bit space to locate valid IDs. > > 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 was thinking of suggesting something similar as an update. > >> Not the strongest guarantee I know. >> >> All platforms currently using SCP (Juno R0 and R1) do indeed expose >> contiguous identifiers. > > IMO, Linux drivers should be coded to the standard or written > specification (where they are available) not the particular > implementations available. > >> > >> > [1] http://community.arm.com/servlet/JiveServlet/download/8401-40-18262/DUI0922A_scp_message_interface.pdf >> [2] http://arminfo.emea.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/ch03s02s21.html >> [3] http://arminfo.emea.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/BABCCCJJ.html > > I think those links are on ARM's intranet, they return NXDOMAIN for me. Apologies, the below should work. [2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/ch03s02s21.html [3] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/BABCCCJJ.html -- 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
