linux-kernel - [PATCH v3 1/2] sysfs/cpu: Use DEVICE_ATTR_RO for nohz

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Message-ID: <20251011011830.6670-2-atomlin@atomlin.com>
Date: Fri, 10 Oct 2025 21:18:29 -0400
From: Aaron Tomlin <atomlin@...mlin.com>
To: gregkh@...uxfoundation.org,
	nathan@...nel.org,
	rafael@...nel.org,
	dakr@...nel.org
Cc: riel@...riel.com,
	frederic@...nel.org,
	atomlin@...mlin.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/2] sysfs/cpu: Use DEVICE_ATTR_RO for nohz_full attribute

The /sys/devices/system/cpu/nohz_full file is a read-only attribute that
reports the CPUs configured for tickless operation (CONFIG_NO_HZ_FULL=y).

The current definition uses the generic DEVICE_ATTR macro, which
unnecessarily requires specifying the file mode (0444) and a NULL
store operation pointer.

This patch converts the definition to use the dedicated DEVICE_ATTR_RO
macro. This correctly expresses the read-only nature of the attribute,
removes the redundant mode field, and simplifies the code. As a related
cleanup, rename the show function from print_cpus_nohz_full() to the
standard nohz_full_show() for consistency with common sysfs attribute
naming conventions.

Signed-off-by: Aaron Tomlin <atomlin@...mlin.com>
---
 drivers/base/cpu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index fa0a2eef93ac..c792ec66462d 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -301,12 +301,13 @@ static ssize_t print_cpus_isolated(struct device *dev,
 static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);

 #ifdef CONFIG_NO_HZ_FULL
-static ssize_t print_cpus_nohz_full(struct device *dev,
-				    struct device_attribute *attr, char *buf)
+static ssize_t nohz_full_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
 {
 	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
 }
-static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
+static DEVICE_ATTR_RO(nohz_full);
 #endif

 #ifdef CONFIG_CRASH_HOTPLUG
-- 
2.49.0