| Message ID | 1360325980-19089-1-git-send-email-dave.martin@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Fri, Feb 08, 2013 at 12:19:40PM +0000, Dave Martin wrote: > It is reasonable for loadable modules to be CPU topology aware > (particular examples include cpufreq and cpuidle drivers). > > This patch exports a new function cpu_get_hwid(cpu) to provide > suitable read-only access outside vmlinux. And we have an export with no user... where are the patches which illustrate its usage?
On Fri, Feb 08, 2013 at 12:26:04PM +0000, Russell King - ARM Linux wrote: > On Fri, Feb 08, 2013 at 12:19:40PM +0000, Dave Martin wrote: > > It is reasonable for loadable modules to be CPU topology aware > > (particular examples include cpufreq and cpuidle drivers). > > > > This patch exports a new function cpu_get_hwid(cpu) to provide > > suitable read-only access outside vmlinux. > > And we have an export with no user... where are the patches which > illustrate its usage? That's a fair point. The background is that ARM have an out-of-tree profiling driver, which may need to look at cpu_logical_map in the presence of the big.LITTLE in-kernel switcher code. Although there is no in-tree code using this yet, the usage seems legitimate. If there are outstanding concerns about this, this patch could stay out-of-tree too, but said driver would only work with a modified kernel in that case. If this is not considered relevant to the kernel proper yet, then it could be posted via the big.LITTLE in-kernel switcher series when those are finally published, since it is this that causes cpu_logical_map to change in ways that a few specialised drivers may need to respond to. Without the switcher, no code should need to look at cpu_logical_map (the present situation). (Nico, please shout if you have any concerns about that approach.) Cheers ---Dave
diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h index aaa61b6..518e466 100644 --- a/arch/arm/include/asm/smp_plat.h +++ b/arch/arm/include/asm/smp_plat.h @@ -66,4 +66,7 @@ static inline int get_logical_index(u32 mpidr) return -EINVAL; } +/* Read-only accessor for use by modules: */ +int cpu_get_hwid(int cpu); + #endif diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index 3f6cbb2..1ac5e8b 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -429,6 +429,13 @@ void cpu_init(void) int __cpu_logical_map[NR_CPUS]; +/* Read-only accessor for use by modules: */ +int cpu_get_hwid(int cpu) +{ + return cpu_logical_map(cpu); +} +EXPORT_SYMBOL_GPL(cpu_get_hwid); + void __init smp_setup_processor_id(void) { int i;
It is reasonable for loadable modules to be CPU topology aware (particular examples include cpufreq and cpuidle drivers). This patch exports a new function cpu_get_hwid(cpu) to provide suitable read-only access outside vmlinux. Signed-off-by: Dave Martin <dave.martin@linaro.org> --- Modules using this function will be arch-dependent and highly coupled to the kernel, so cpu_get_hwid() shouldn't be considered a stable API, especially while the details of kernel topology awareness are still under discussion: therefore, export only to GPL code for now. arch/arm/include/asm/smp_plat.h | 3 +++ arch/arm/kernel/setup.c | 7 +++++++ 2 files changed, 10 insertions(+), 0 deletions(-)