RISC-V: Extract multi-letter extension names from "riscv, isa"

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.

Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Tsukasa OI <research_trasio@irq.a4lg.com>
[Improved commit text and comments]
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 72c5f6ef56b5ab705bef5debe94d8a235caca6b4..b0df7eff47f77b9c5a79308a04f493846c1b3060 100644 (file)
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -124,8 +124,28 @@ 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;
+                               /* 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))) {
@@ -151,14 +171,13 @@ void __init riscv_fill_hwcap(void)
                        }
                        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'));
+                       }
                }
 
                /*