On Tue, 2018-07-03 at 13:30 -0600, Rob Herring wrote: > On Fri, Jun 22, 2018 at 02:37:55PM +1000, Benjamin Herrenschmidt wrote: > > This represents a physical chip in the system and allows > > a stable numbering scheme to be passed to udev for userspace > > to recognize which chip is which. > > I'm sure you're aware, stable numbers is generally not something the > kernel guarantees... This has nothing to do with any kernel guarantee. Not sure what you are mixing up here :-) The IDs will get exposed via sysfs in order to allow udev rules to create appropriate symlinks such as by-id or by-path as is traditional (we haven't completely decided some of the udev side details yet) > In the cases where we do have them, we've used aliases. This is necessary, though Aliases may do the job too. This is the device-tree that represents the "host" system that the BMC is managing. We need to be able to identify using a stable numbering scheme the processors on the FSI topology otherwise we would do "interesting" things such as turn the fan for CPU 1 when CPU 0 gets hot :-) (This is just a silly example, there are plenty of other reasons why we need to understand the HW topology of a given system, including debuggers using FSI as a backend etc...) Traditionally POWER has used ibm,chip-id properties for the host side, so I just did something similar here for the BMC side, but I can look into using aliases if you prefer. Note: I'm not sure what you have against DT provided names or IDs, this has been a rather standard way of doing things even before we did the FDT. For example that's what slot-names properties are for, or location codes etc... Yes we invented that alias trick later on but it's not necessarily the best approach (in fact I don't really like it to be honest). Cheers, Ben. > > > Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > > --- > > Documentation/devicetree/bindings/fsi/fsi.txt | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/fsi/fsi.txt b/Documentation/devicetree/bindings/fsi/fsi.txt > > index ab516c673a4b..afb4eccab131 100644 > > --- a/Documentation/devicetree/bindings/fsi/fsi.txt > > +++ b/Documentation/devicetree/bindings/fsi/fsi.txt > > @@ -83,6 +83,10 @@ addresses and sizes in the slave address space: > > #address-cells = <1>; > > #size-cells = <1>; > > > > +Optionally, a slave can provide a global unique chip ID which is used to > > +identify the physical location of the chip in a system specific way > > + > > + chip-id = <0>; > > > > FSI engines (devices) > > --------------------- > > @@ -125,6 +129,7 @@ device tree if no extra platform information is required. > > reg = <0 0>; > > #address-cells = <1>; > > #size-cells = <1>; > > + chip-id = <0>; > > > > /* FSI engine at 0xc00, using a single page. In this example, > > * it's an I2C master controller, so subnodes describe the > > -- > > 2.17.1 > > > > -- > > 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 -- 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
