Requesting a GPIO that hasn't been registered yet

[Bill Gatliff]

Guys:


I'm sure this is a FAQ, but I can't seem to find the answer.  I'm happy
to RTFM, if someone can please tell me where the FM is.  :)

I'm adding device table support to gpio_keys.  The target is an
MPC5200B.  I have statements in my dts file that look like this:

...
        i2c at 3d40 {
            #address-cells = <1>;
            #size-cells = <0>;
            compatible = "fsl,mpc5200b-i2c","fsl,mpc5200-i2c","fsl-i2c";
            reg = <0x3d40 0x40>;
            interrupts = <2 16 0>;
...
            lext60: max7314 at 60 {
                compatible = "maxim,max7314","phillips,pca953x";
                reg = <0x60>;
                gpio-controller;
                #gpio-cells = <2>;
            };
        };
...
        gpio-keys {
              compatible = "gpio-keys";
              encoder_button {
                     gpios = <&lext60 12 0>;
                     code = <28>;
                     type = <1>;
                     active-low = <0>;
                     wakeup = <0>;
                     debounce-interval = <0>;
                     rep = <0>;
                     };
             };

In other words, the GPIO pin I'm using for the key is one of the bits on
my pca953x GPIO expander chip.

The above would all be great, except that I haven't come up with a way
to make sure that my encoder_button doesn't try to probe before lext60
is available.  In fact, I'm consistently getting initialization in the
wrong order!

Eventually the GPIO expander chip gets plugged in, because I can see it
show up in sysfs.  And what's really odd is, I recently made similar
mods to gpio_leds and they are working fine--- although the GPIO pin is
on a pca953x at address 20, instead of 60.  I'm at a loss to explain why
one works, but the other doesn't.  And I don't know how to really fix
this problem for good!

Any suggestions?  Thanks!!


b.g.

-- 
Bill Gatliff
bgat at billgatliff.com