To amplify on Jake’s reply: You send the IOCTL_ACPI_EVAL_METHOD to the PDO directly below your FDO. In other words, you send it DOWN the stack to the device object immediately below yours. You get this pointer back as the return value from IoAttachDeviceToDeviceStack().
BTW, you *really* want to be doing all this using KMDF, not using WDM. Life will be sooooooo much easier for you.
Peter
OSR