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Subject[PATCH] [RFC] Expose _SUN in /proc/acpi/processor/<...>/info

I'm looking for comments on the following patch that exposes _SUN
on processor objects in /proc/acpi/processor/<...>/info.

This didn't get many comments on the linux-acpi list, so I'm
sending to a wider distribution.

I notice that acpiphp exposes _SUN for (hotpluggable) PCI slots
in /sys/bus/pci/slots/N/, where N is the value of _SUN. I'm not
so sure we want to go *exactly* in the same direction for CPUs,

- x86 systems might not implement _SUN for processors
- ia64 systems that implement ACPI 2.x do not have unique
values for _SUN across the entire system

Nonetheless, even non-unique values of _SUN are still helpful for
userspace to figure out which physical socket a CPU might be in,
especially when combined with information from /proc/cpuinfo.




From: Alex Chiang <>

On platforms that provide _SUN for the processor object, higher
level software can consume the data to learn physical topology
information, so let's expose it.

Platforms that do not implement _SUN will see <not supported>.

Signed-off-by: Alex Chiang <>
drivers/acpi/processor_core.c | 11 +++++++++++
include/acpi/processor.h | 1 +
2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 235a51e..86cb41a 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -302,6 +302,11 @@ static int acpi_processor_info_seq_show(struct seq_file *seq, void *offset)
pr->flags.throttling ? "yes" : "no",
pr->flags.limit ? "yes" : "no");

+ if (pr->sun == -1)
+ seq_printf(seq, "slot user number: <not supported>\n");
+ else
+ seq_printf(seq, "slot user number: %d\n", (int)pr->sun);
return 0;
@@ -590,6 +595,12 @@ static int acpi_processor_get_info(struct acpi_processor *pr, unsigned has_uid)
ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Processor [%d:%d]\n", pr->id,

+ status = acpi_evaluate_object(pr->handle, "_SUN", NULL, &buffer);
+ if (ACPI_FAILURE(status))
+ object.integer.value = -1;
+ pr->sun = object.integer.value;
if (!object.processor.pblk_address)
else if (object.processor.pblk_length != 6)
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 26d79f6..81792c6 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -210,6 +210,7 @@ struct acpi_processor {
u32 acpi_id;
u32 id;
u32 pblk;
+ acpi_native_int sun;
int performance_platform_limit;
int throttling_platform_limit;
/* 0 - states 0..n-th state available */
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