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| author | Andrew Jones <ajones@ventanamicro.com> | 2023-11-22 17:47:02 +0100 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-01-03 03:36:47 -0800 |
| commit | 36d842d654beba970e74ff0f6016c93623b82d37 (patch) | |
| tree | b3e0f1a94f0ca29f7e83049b9e7bc3e14430824d /Documentation/arch/riscv | |
| parent | b85ea95d086471afb4ad062012a4d73cd328fa86 (diff) | |
| download | linux-stable-36d842d654beba970e74ff0f6016c93623b82d37.tar.gz linux-stable-36d842d654beba970e74ff0f6016c93623b82d37.tar.bz2 linux-stable-36d842d654beba970e74ff0f6016c93623b82d37.zip | |
RISC-V: hwprobe: Clarify cpus size parameter
The "count" parameter associated with the 'cpus' parameter of the
hwprobe syscall is the size in bytes of 'cpus'. Naming it 'cpu_count'
may mislead users (it did me) to think it's the number of CPUs that
are or can be represented by 'cpus' instead. This is particularly
easy (IMO) to get wrong since 'cpus' is documented to be defined by
CPU_SET(3) and CPU_SET(3) also documents a CPU_COUNT() (the number
of CPUs in set) macro. CPU_SET(3) refers to the size of cpu sets
with 'setsize'. Adopt 'cpusetsize' for the hwprobe parameter and
specifically state it is in bytes in Documentation/riscv/hwprobe.rst
to clarify.
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20231122164700.127954-7-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation/arch/riscv')
| -rw-r--r-- | Documentation/arch/riscv/hwprobe.rst | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst index 7b2384de471f..132e9acaa8f4 100644 --- a/Documentation/arch/riscv/hwprobe.rst +++ b/Documentation/arch/riscv/hwprobe.rst @@ -12,7 +12,7 @@ is defined in <asm/hwprobe.h>:: }; long sys_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count, - size_t cpu_count, cpu_set_t *cpus, + size_t cpusetsize, cpu_set_t *cpus, unsigned int flags); The arguments are split into three groups: an array of key-value pairs, a CPU @@ -20,12 +20,13 @@ set, and some flags. The key-value pairs are supplied with a count. Userspace must prepopulate the key field for each element, and the kernel will fill in the value if the key is recognized. If a key is unknown to the kernel, its key field will be cleared to -1, and its value set to 0. The CPU set is defined by -CPU_SET(3). For value-like keys (eg. vendor/arch/impl), the returned value will -be only be valid if all CPUs in the given set have the same value. Otherwise -1 -will be returned. For boolean-like keys, the value returned will be a logical -AND of the values for the specified CPUs. Usermode can supply NULL for cpus and -0 for cpu_count as a shortcut for all online CPUs. There are currently no flags, -this value must be zero for future compatibility. +CPU_SET(3) with size ``cpusetsize`` bytes. For value-like keys (eg. vendor, +arch, impl), the returned value will only be valid if all CPUs in the given set +have the same value. Otherwise -1 will be returned. For boolean-like keys, the +value returned will be a logical AND of the values for the specified CPUs. +Usermode can supply NULL for ``cpus`` and 0 for ``cpusetsize`` as a shortcut for +all online CPUs. There are currently no flags, this value must be zero for +future compatibility. On success 0 is returned, on failure a negative error code is returned. |