Subject: [PATCH 05/18] cpuidle: make a single register function for all

From: [email-masked] (Rob Herring)
Date: Wed, 10 Apr 2013 09:59:45 -0500

On 04/10/2013 09:22 AM, Daniel Lezcano wrote:
> The usual scheme to initialize a cpuidle driver on a SMP is:
> 
> 	cpuidle_register_driver(drv);
> 	for_each_possible_cpu(cpu) {
> 		device = &per_cpu(cpuidle_dev, cpu);
> 		cpuidle_register_device(device);
> 	}
> 
> This code is duplicated in each cpuidle driver.
> 
> On UP systems, it is done this way:
> 
> 	cpuidle_register_driver(drv);
> 	device = &per_cpu(cpuidle_dev, cpu);
> 	cpuidle_register_device(device);
> 
> On UP, the macro 'for_each_cpu' does one iteration:
> 
> #define for_each_cpu(cpu, mask)                 \
>         for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
> 
> Hence, the initialization loop is the same for UP than SMP.
> 
> Beside, we saw different bugs / mis-initialization / return code unchecked in
> the different drivers, the code is duplicated including bugs. After fixing all
> these ones, it appears the initialization pattern is the same for everyone.
> 
> Let's add a wrapper function doing this initialization with a cpumask parameter
> for the coupled idle states and use it for all the drivers.
> 
> That will save a lot of LOC, consolidate the code, and the modifications in the
> future could be done in a single place. Another benefit is the consolidation of
> the cpuidle_device variable which is now in the cpuidle framework and no longer
> spread accross the different arch specific drivers.
> 
> Signed-off-by: Daniel Lezcano <[email-masked]>
> ---

Perhaps my ack was too quick...

> +int cpuidle_register(struct cpuidle_driver *drv,
> +		     const struct cpumask *const coupled_cpus)
> +{
> +	int ret, cpu;
> +	struct cpuidle_device *device;
> +
> +	ret = cpuidle_register_driver(drv);
> +	if (ret) {
> +		printk(KERN_ERR "failed to register cpuidle driver\n");
> +		return ret;
> +	}
> +
> +	for_each_possible_cpu(cpu) {
> +		device = &per_cpu(cpuidle_dev, cpu);
> +		device->cpu = cpu;
> +#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
> +		device->coupled_cpus = *coupled_cpus;

This needs a NULL check. CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED is most
likely going to be enabled with multi-platform kernels and this will crash.

Also, I think typically struct copies have a note that it is copy.

Rob