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Wed, 10 Dec 2025 01:43:34 -0800 (PST) Received: from localhost.localdomain ([38.134.139.135]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34a47bb279fsm2597892a91.1.2025.12.10.01.43.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Dec 2025 01:43:34 -0800 (PST) From: Dharanitharan R To: gregkh@linuxfoundation.org Cc: linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, david.laight.linux@gmail.com, dharanitharan725@gmail.com Subject: [PATCH v3] staging: vme_user: simplify bus number allocation using ffz() Date: Wed, 10 Dec 2025 09:42:08 +0000 Message-ID: <20251210094207.33671-2-dharanitharan725@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" David Laight pointed out that the loop in vme_register_bridge() is effectively searching for the first zero bit in vme_bus_numbers. Add a check for vme_bus_numbers =3D=3D ~0UL before calling ffz(). Replace the manual loop with ffz() and use BIT(n) for consistency. Suggested-by: David Laight Signed-off-by: Dharanitharan R --- drivers/staging/vme_user/vme.c | 15 +++++++++++++---------- 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/drivers/staging/vme_user/vme.c b/drivers/staging/vme_user/vme.c index 2095de72596a..45381e677475 100644 --- a/drivers/staging/vme_user/vme.c +++ b/drivers/staging/vme_user/vme.c @@ -1765,16 +1765,19 @@ int vme_register_bridge(struct vme_bridge *bridge) int ret =3D -1; =20 mutex_lock(&vme_buses_lock); - for (i =3D 0; i < sizeof(vme_bus_numbers) * 8; i++){ - if ((vme_bus_numbers & (1 << i)) =3D=3D 0) { - vme_bus_numbers |=3D (1 << i); - bridge->num =3D i; - INIT_LIST_HEAD(&bridge->devices); - list_add_tail(&bridge->bus_list, &vme_bus_list); - ret =3D 0; - break; - } + /* Ensure we have a free slot before using ffz() */ + if (vme_bus_numbers =3D=3D ~0UL) + goto out; /* No free bus number */ + + /* Find the first clear bit */ + i =3D ffz(vme_bus_numbers); + + vme_bus_numbers |=3D BIT(i); + bridge->num =3D i; + INIT_LIST_HEAD(&bridge->devices); + list_add_tail(&bridge->bus_list, &vme_bus_list); + ret =3D 0; + +out: mutex_unlock(&vme_buses_lock); =20 return ret; @@ -1787,7 +1790,7 @@ void vme_unregister_bridge(struct vme_bridge *bridge) struct vme_dev *tmp; =20 mutex_lock(&vme_buses_lock); - vme_bus_numbers &=3D ~(1 << bridge->num); + vme_bus_numbers &=3D ~BIT(bridge->num); list_for_each_entry_safe(vdev, tmp, &bridge->devices, bridge_list) { list_del(&vdev->drv_list); list_del(&vdev->bridge_list); --=20 2.43.0