On Tue, 3 Mar 2015 10:32:24 +0100 , Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > This defines a new compatible option for MFD devices "simple-mfd" that will > make the OF core spawn child devices for all subnodes of that MFD device. > It is optional but handy for things like syscon and possibly other > simpler MFD devices. > > Since there was no file to put the documentation in, I took this opportunity > to make a small writeup on MFD devices and add the compatible definition > there. > > Suggested-by: Lee Jones <lee.jones@xxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Devicetree <devicetree@xxxxxxxxxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Cc: Grant Likely <grant.likely@xxxxxxxxxx> > Cc: Pawel Moll <pawel.moll@xxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx> > Cc: Kumar Gala <galak@xxxxxxxxxxxxxx> > Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > --- > I make the patch to the OF core in this one, it makes much more sense since > it's a oneliner > > Lee: this is a (tested!) implementation of your suggestion for simple-mfd. > If you can eventually ACK this from the MFD side, I think it should be > funneled through the ARM SoC tree. > > Grant/Rob: if either of you can ACK the change to the OF core likewise it can > be taken through ARM SoC. > > DT binings maintainers: there is some background discussion on this here: > http://marc.info/?l=linux-arm-kernel&m=142486676603889&w=2 > http://marc.info/?l=devicetree&m=142166313621469&w=2 > --- > Documentation/devicetree/bindings/mfd/mfd.txt | 40 +++++++++++++++++++++++++++ > drivers/of/platform.c | 1 + > 2 files changed, 41 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mfd/mfd.txt > > diff --git a/Documentation/devicetree/bindings/mfd/mfd.txt b/Documentation/devicetree/bindings/mfd/mfd.txt > new file mode 100644 > index 000000000000..cc057438abe8 > --- /dev/null > +++ b/Documentation/devicetree/bindings/mfd/mfd.txt > @@ -0,0 +1,40 @@ > +Multi-Function Devices (MFD) > + > +These devices comprise a nexus for heterogeneous hardware blocks spawning > +multiple child devices. > + > +A typical MFD can be: > + > +- A mixed signal ASIC on an external bus, sometimes a PMIC (power management > + integrated circuit) that is manufactured in a lower technology node (rough > + silicon) that handles analog drivers for things like audio amplifiers, LED > + drivers, level shifters, PHY (physical interfaces to things like USB or > + ethernet), regulators etc. > + > +- A range of memory registers containing "miscellaneous system registers" also > + known as a system controller "syscon" or any other memory range containing a > + mix of unrelated registers. > + > +Optional properties: > + > +- compatible : "simple-mfd" - this signifies that the operating system should > + spawn child devices for all the subnodes of the MFD device akin to how > + "simple-bus" inidicates when to spawn children for a simple memory-mapped > + bus. For more complex devices, when the nexus driver has to probe registers > + to figure out what children exist etc, this should not be used. In the latter > + case the child devices will be instantiated by the operating system. > + > +Example: > + > +foo@1000 { > + compatible = "syscon", "simple-mfd"; > + reg = <0x010000 0x1000>; > + > + led@08.0 { > + compatible = "register-bit-led"; > + offset = <0x08>; > + mask = <0x01>; > + label = "myled"; > + default-state = "on"; > + }; > +}; > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index b189733a1539..969ba4e1460c 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -26,6 +26,7 @@ > > const struct of_device_id of_default_bus_match_table[] = { > { .compatible = "simple-bus", }, > + { .compatible = "simple-mfd", }, > #ifdef CONFIG_ARM_AMBA > { .compatible = "arm,amba-bus", }, > #endif /* CONFIG_ARM_AMBA */ Alright, so: Acked-by: Grant Likely <grant.likely@xxxxxxxxxx> However, I think this is going to lead to a future problem. It solves the immediate case of getting an MFD device to be auto populated when the kernel doesn't need to immediately do something. However, I can forsee a situation where the device can be supported by simple-mfd, but at some point it is discovered that better features can be enabled if the mfd device has a proper driver. If/when we get into that situation, the above still works, but we're going to need to add a blacklist match table so that simple-mfd can be overridden by a more-specific compatible value. I don't have any problems with doing that, but someone needs to implement it. g. -- 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
