[PATCH v3 3/3] RISC-V: Extract multi-letter extension names from "riscv, isa"

Tsukasa OI
2022-02-12T06:30:36Z

Currently, there is no usage for version numbers in extensions as
any ratified non base ISA extension will always at v1.0.

Extract the extension names in place for future parsing.

Signed-off-by: Tsukasa OI <research_trasio@irq.a4lg.com>
[Improved commit text and comments]
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
arch/riscv/kernel/cpufeature.c | 38 ++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 9d5448542226..cd9eb34f8d11 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -119,9 +119,28 @@ void __init riscv_fill_hwcap(void)
ext_long = true;
/* Multi-letter extension must be delimited */
for (; *isa && *isa != '_'; ++isa)
- if (!islower(*isa) && !isdigit(*isa))
+ if (unlikely(!islower(*isa)
+ && !isdigit(*isa)))
ext_err = true;
- /* ... but must be ignored. */
+ /* Parse backwards */
+ ext_end = isa;
+ if (unlikely(ext_err))
+ break;
+ if (!isdigit(ext_end[-1]))
+ break;
+ /* Skip the minor version */
+ while (isdigit(*--ext_end))
+ ;
+ if (ext_end[0] != 'p'
+ || !isdigit(ext_end[-1])) {
+ /* Advance it to offset the pre-decrement */
+ ++ext_end;
+ break;
+ }
+ /* Skip the major version */
+ while (isdigit(*--ext_end))
+ ;
+ ++ext_end;
break;
default:
if (unlikely(!islower(*ext))) {
@@ -131,6 +150,7 @@ void __init riscv_fill_hwcap(void)
/* Find next extension */
if (!isdigit(*isa))
break;
+ /* Skip the minor version */
while (isdigit(*++isa))
;
if (*isa != 'p')
@@ -139,20 +159,20 @@ void __init riscv_fill_hwcap(void)
--isa;
break;
}
+ /* Skip the major version */
while (isdigit(*++isa))
;
break;
}
if (*isa != '_')
--isa;
- /*
- * TODO: Full version-aware handling including
- * multi-letter extensions will be added in-future.
- */
- if (ext_err || ext_long)
+
+ if (unlikely(ext_err))
continue;
- this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
- this_isa |= (1UL << (*ext - 'a'));
+ if (!ext_long) {
+ this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
+ this_isa |= (1UL << (*ext - 'a'));
+ }
}

/*
--
2.32.0