On Mon, Oct 17, 2016 at 04:46:49PM +0100, Juri Lelli wrote:
> +#ifdef CONFIG_PROC_SYSCTL
> +#include <asm/cpu.h>
> +#include <linux/string.h>
Include files at the top of the file please. No need to ifdef them.
They're sorted alphabetically, so new additions should be alphabetical.
(That's a general rule - if something is already alphabetical, do not
make it non-alphabetical.)
> +static ssize_t show_cpu_capacity(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct cpu *cpu = container_of(dev, struct cpu, dev);
> + ssize_t rc;
> + int cpunum = cpu->dev.id;
> + unsigned long capacity = arch_scale_cpu_capacity(NULL, cpunum);
> +
> + rc = sprintf(buf, "%lu\n", capacity);
> +
> + return rc;
Way too many lines for such a simple function. This can be simplified
to just:
struct cpu *cpu = container_of(dev, struct cpu, dev);
return sprintf(buf, "%lu\n", arch_scale_cpu_capacity(NULL, cpu->dev.id);
If you don't like the last line ending on column 79, then feel free to
break it across two lines after the format string.
> +}
> +
> +static ssize_t store_cpu_capacity(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf,
> + size_t count)
> +{
> + struct cpu *cpu = container_of(dev, struct cpu, dev);
> + int this_cpu = cpu->dev.id, i;
> + unsigned long new_capacity;
> + ssize_t ret;
> +
> + if (count) {
> + char *p = (char *) buf;
> +
> + ret = kstrtoul(p, 0, &new_capacity);
Unnecessary cast - kstrtoul takes a const char pointer, and in any case
it's really bad form to cast away the "const-ness" of any pointer. So,
just:
if (count) {
ret = kstrtoul(buf, 0, &new_capacity);
should work just fine.
> + if (ret)
> + return ret;
> + if (new_capacity > SCHED_CAPACITY_SCALE)
> + return -EINVAL;
> +
> + mutex_lock(&cpu_scale_mutex);
> + for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
> + set_capacity_scale(i, new_capacity);
> + mutex_unlock(&cpu_scale_mutex);
> + }
> +
> + return count;
> +}
> +
> +static DEVICE_ATTR(cpu_capacity,
> + 0644,
> + show_cpu_capacity,
> + store_cpu_capacity);
There's a move to use the named DEVICE_ATTR_RW() for this kind of thing,
it'll want the functions named xxx_show() and xxx_store(). I see
there's some recent patches to do this conversion across the kernel, so
this should probably be done before submission.
> +
> +static int register_cpu_capacity_sysctl(void)
> +{
> + int i;
> + struct device *cpu;
> +
> + for_each_possible_cpu(i) {
> + cpu = get_cpu_device(i);
> + if (!cpu) {
> + pr_err("%s: too early to get CPU%d device!\n",
> + __func__, i);
> + continue;
> + }
> + device_create_file(cpu, &dev_attr_cpu_capacity);
> + }
> +
> + return 0;
> +}
> +late_initcall(register_cpu_capacity_sysctl);
Hmm, this is really weird. topology_init() in arch/arm/kernel/setup.c
is where these devices get created, and they're created at
subsys_initcall() time. By that point, the list of possible CPUs has
to be static, it's not going to change. I don't see why this has to be
done at late_initcall() - and since topology.c will be linked after
setup.c, I don't see why it shouldn't be at subsys_initcall() level to
follow on after topology_init().
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