Re: [RFC PATCH 2/3] pinctrl: at91: add support for generic pinconf

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 27/08/2013 05:54, Stephen Warren wrote:
On 08/26/2013 12:45 PM, boris brezillon wrote:
Hello Jean-Christophe,

Le 26/08/2013 19:53, Jean-Christophe PLAGNIOL-VILLARD a écrit :
On 23:37 Sat 24 Aug     , Boris BREZILLON wrote:
Add support for generic pin configuration to pinctrl-at91 driver.
...
a/Documentation/devicetree/bindings/pinctrl/atmel,at91-pinctrl.txt
...
configures various pad settings
   such as pull-up, multi drive, etc.
     Required properties for iomux controller:
-- compatible: "atmel,at91rm9200-pinctrl"
+- compatible: "atmel,at91rm9200-pinctrl" or "atmel,at91sam9x5-pinctrl".
+  Add "generic-pinconf" to the compatible string list to use the
generic pin
...
+pinctrl@fffff400 {
+    #address-cells = <1>;
+    #size-cells = <1>;
+    ranges;
+    compatible = "atmel,at91rm9200-pinctrl", "generic-pinconf",
"simple-bus";
nack your break the backword compatibility

if we use a old kernel with this new dt nothing will work
as the old kernel will never known the the "generic-pinconf" means
anything
Your're right, I didn't think of this case (old kernel with new dt).
Well, just to be clear: If a new DT uses a new compatible value of any
kind, be it adding "generic-pinconf" or switching to "foo-yyy" rather
than "foo-yyy", it won't be compatible... That somewhat implies that you
can't ever replace an old binding with something new.

That's absolutely right, however the behaviour won't be the same in both cases.

1) If your (new) dt defines its pinctrl using the "foo-pinconf" compatible string and your (old) kernel does not support it, the pinctrl will never probe the pinctrl definitions. Moreover, if you want to define both old ("foo-pinctrl") and new ("foo-pinconf") pinctrl definitions in your dt in order to support several kernel versions, nothing prevents you
    from doing it.

2) In the other hand, if you use an additional "generic-pinconf" compatible string to signify wether or not the pinctrl definition use the generic pinconf dt binding, the (old) kernel will probe the pinctrl definitions, ignore the "generic-pinconf" string, and fail when parsing the pinctrl configuration nodes (which are invalid pinctrl function nodes in the current dt binding). We have the same problem when using the 'atmel,generic-pinconf' property inside a pinctrl node:
    old kernels won't take this property into account.

--
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




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux