Re: [RFC PATCH] ARM: pmu: add OF match support

Will,

On 02/09/2011 03:51 AM, Will Deacon wrote:

Hi Rob,

quoted

Add OF match table to enable OF style driver binding. The dts entry is like
this:

pmu {
	compatible = "arm,pmu";
	interrupts =<100 101>;
};

The use of pdev->id as an index breaks with OF device binding. Change to use
a counter instead. If more than 1 pmu device is ever really supported, a
better solution to match users with particular pmu is probably needed.

We will want to support multiple PMU devices in the near future but
this is currently blocked on userspace issues. One such device would
be the event counters on the PL310, which could be used to complement
the CPU PMU on the Cortex-A9.

I don't like the idea of a counter as it forces platforms to register
their devices in a specific order. Is it possible to separate different
types of PMU in the device tree and then have pmu.c work out what to do
with them?

Yes, they are easily distinguished by the compatible strings. Adding a 
pmu_get function which returns the device based on a string or 
capabilities may be a better solution. If you had 2 pmu's of the same 
type, the current code would break.

In any case, how about this:

static int __devinit pmu_device_probe(struct platform_device *pdev)
{
	enum arm_pmu_type type = pdev->id;

	if (of_device_is_compatible(pdev->dev.of_node, "arm,pmu"))
		type = ARM_PMU_DEVICE_CPU;

	if (type < 0 || type >= ARM_NUM_PMU_DEVICES) {
		pr_warning("received registration request for unknown "
				"device %d\n", pdev->id);
		return -EINVAL;
	}

	if (pmu_devices[type])
		pr_warning("registering new PMU device type %d overwrites "
				"previous registration!\n", type);
	else
		pr_info("registered new PMU device of type %d\n",
				type);

	pmu_devices[type] = pdev;
	return 0;
}

Rob