Add description of the single-letter B extension for Bit Manipulation.
B is mandatory for RVA23U64.
The B extension is ratified in the 20240411 version of the unprivileged
ISA specification. According to the ratified spec, the B standard
extension comprises instructions provided by the Zba, Zbb, and Zbs
extensions.
Add two-way dependency check to enforce that B implies Zba/Zbb/Zbs; and
when Zba/Zbb/Zbs (all of them) are specified, then B must be added too.
The reason why B/Zba/Zbb/Zbs must coexist at the same time is that
unlike other single-letter extensions, B was ratified (Apr/2024) much
later than its component extensions Zba/Zbb/Zbs (Jun/2021).
When "b" is specified, zba/zbb/zbs must be present to ensure
backward compatibility with existing software and kernels that only
look for the explicit component strings.
When all three components zba/zbb/zbs are specified, "b" should also be
present. Making "b" mandatory when all three components are present.
Existing devicetrees with zba/zbb/zbs but without "b" will generate
warnings that can be fixed in follow-up patches.
Signed-off-by: Guodong Xu <guodong@riscstar.com>
---
v4: No change.
v3: Update the commit message to explain the retionale why B and
Zba/Zbb/Zbs should all exist in DT.
v2: New patch.
---
.../devicetree/bindings/riscv/extensions.yaml | 31 ++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
index b615083f2544..f671299ac819 100644
--- a/Documentation/devicetree/bindings/riscv/extensions.yaml
+++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
@@ -109,6 +109,13 @@ properties:
The standard C extension for compressed instructions, as ratified in
the 20191213 version of the unprivileged ISA specification.
+ - const: b
+ description:
+ The standard B extension for bit manipulation instructions, as
+ ratified in the 20240411 version of the unprivileged ISA
+ specification. The B standard extension comprises instructions
+ provided by the Zba, Zbb, and Zbs extensions.
+
- const: v
description:
The standard V extension for vector operations, as ratified
@@ -752,6 +759,30 @@ properties:
then:
contains:
const: f
+ # B comprises Zba, Zbb, and Zbs
+ - if:
+ contains:
+ const: b
+ then:
+ allOf:
+ - contains:
+ const: zba
+ - contains:
+ const: zbb
+ - contains:
+ const: zbs
+ # Zba, Zbb, Zbs together require B
+ - if:
+ allOf:
+ - contains:
+ const: zba
+ - contains:
+ const: zbb
+ - contains:
+ const: zbs
+ then:
+ contains:
+ const: b
# Zcb depends on Zca
- if:
contains:
--
2.43.0