u-boot version: 2021.07-RC3

[Description]
Build and run u-boot:

make sandbox_defconfig
make
./u-boot -d u-boot.dtb

Type the following on the command-line:

=> demo hello 5

I Got the following Error:

Command 'demo' failed: Error -22

[Analysis]
Index 5 is the device named 'hexagon' defined in arch/sandbox/dts/sandbox.dtsi:

hexagon {
        compatible = "demo-simple";
        colour = "white";
        sides = <6>;
    };

device_probe will call of_to_plat, which finally call demo_parse_dt in drivers/demo/demo-uclass.c.

int demo_parse_dt(struct udevice *dev)
{
    struct dm_demo_pdata *pdata = dev_get_plat(dev);
    int dn = dev_of_offset(dev);

    pdata->sides = fdtdec_get_int(gd->fdt_blob, dn, "sides", 0);
    pdata->colour = fdt_getprop(gd->fdt_blob, dn, "colour", NULL);
    if (!pdata->sides || !pdata->colour) {
        debug("%s: Invalid device tree data\n", __func__);
        return -EINVAL;
    }

    return 0;
}

Here, I got 0 for pdata->sides, and NULL for pdata->colour. Seem that fdtdec_get_int and fdt_getprop hadn't get the correct values from device tree.
I notice that dn here is in int type, but dev->node_.of_offset is in long type. So dn contains a truncated offset value. However, I'm not sure if the error I got is related to this.