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Fri, 09 Jan 2026 21:19:58 -0800 (PST) From: Guodong Xu Date: Sat, 10 Jan 2026 13:18:18 +0800 Subject: [PATCH v4 06/11] dt-bindings: riscv: Add B ISA extension description Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260110-k3-basic-dt-v4-6-d492f3a30ffa@riscstar.com> References: <20260110-k3-basic-dt-v4-0-d492f3a30ffa@riscstar.com> In-Reply-To: <20260110-k3-basic-dt-v4-0-d492f3a30ffa@riscstar.com> To: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Yixun Lan , Daniel Lezcano , Thomas Gleixner , Samuel Holland , Anup Patel , Greg Kroah-Hartman , Jiri Slaby , Lubomir Rintel , Yangyu Chen Cc: Paul Walmsley , Conor Dooley , Heinrich Schuchardt , Kevin Meng Zhang , Anup Patel , Andrew Jones , devicetree@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, spacemit@lists.linux.dev, linux-serial@vger.kernel.org, Guodong Xu X-Mailer: b4 0.14.3 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 --- 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/Docu= mentation/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 ratif= ied in the 20191213 version of the unprivileged ISA specification. =20 + - 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: --=20 2.43.0