diff options
Diffstat (limited to 'Documentation/cputopology.txt')
-rw-r--r-- | Documentation/cputopology.txt | 26 |
1 files changed, 9 insertions, 17 deletions
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt index b61cb9564023..bd699da24666 100644 --- a/Documentation/cputopology.txt +++ b/Documentation/cputopology.txt | |||
@@ -14,9 +14,8 @@ represent the thread siblings to cpu X in the same physical package; | |||
14 | To implement it in an architecture-neutral way, a new source file, | 14 | To implement it in an architecture-neutral way, a new source file, |
15 | drivers/base/topology.c, is to export the 4 attributes. | 15 | drivers/base/topology.c, is to export the 4 attributes. |
16 | 16 | ||
17 | If one architecture wants to support this feature, it just needs to | 17 | For an architecture to support this feature, it must define some of |
18 | implement 4 defines, typically in file include/asm-XXX/topology.h. | 18 | these macros in include/asm-XXX/topology.h: |
19 | The 4 defines are: | ||
20 | #define topology_physical_package_id(cpu) | 19 | #define topology_physical_package_id(cpu) |
21 | #define topology_core_id(cpu) | 20 | #define topology_core_id(cpu) |
22 | #define topology_thread_siblings(cpu) | 21 | #define topology_thread_siblings(cpu) |
@@ -25,17 +24,10 @@ The 4 defines are: | |||
25 | The type of **_id is int. | 24 | The type of **_id is int. |
26 | The type of siblings is cpumask_t. | 25 | The type of siblings is cpumask_t. |
27 | 26 | ||
28 | To be consistent on all architectures, the 4 attributes should have | 27 | To be consistent on all architectures, include/linux/topology.h |
29 | default values if their values are unavailable. Below is the rule. | 28 | provides default definitions for any of the above macros that are |
30 | 1) physical_package_id: If cpu has no physical package id, -1 is the | 29 | not defined by include/asm-XXX/topology.h: |
31 | default value. | 30 | 1) physical_package_id: -1 |
32 | 2) core_id: If cpu doesn't support multi-core, its core id is 0. | 31 | 2) core_id: 0 |
33 | 3) thread_siblings: Just include itself, if the cpu doesn't support | 32 | 3) thread_siblings: just the given CPU |
34 | HT/multi-thread. | 33 | 4) core_siblings: just the given CPU |
35 | 4) core_siblings: Just include itself, if the cpu doesn't support | ||
36 | multi-core and HT/Multi-thread. | ||
37 | |||
38 | So be careful when declaring the 4 defines in include/asm-XXX/topology.h. | ||
39 | |||
40 | If an attribute isn't defined on an architecture, it won't be exported. | ||
41 | |||