linux-kernel - [PATCH] thermal: sysfs: Return ENODATA instead of EAGAIN for reads

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Message-Id: <20250409-temp-v1-1-9a391d8c60fd@chromium.org>
Date: Wed, 09 Apr 2025 09:13:11 +0000
From: Hsin-Te Yuan <yuanhsinte@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, 
 Lukasz Luba <lukasz.luba@....com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Hsin-Te Yuan <yuanhsinte@...omium.org>
Subject: [PATCH] thermal: sysfs: Return ENODATA instead of EAGAIN for reads

When userspace nonblocking reads temperature via sysfs, EAGAIN error
returned by thermal driver will confuse user from the usual meaning of
EAGAIN, the read would block. Change to throw ENODATA instead of EAGAIN
to userspace. Also, ENODATA more accurately reflects that data is not
currently available.

Signed-off-by: Hsin-Te Yuan <yuanhsinte@...omium.org>
---
 drivers/thermal/thermal_sysfs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 24b9055a0b6c515b865e0d7e2db1d0de176ff767..3d1713e053dfb867933d95131f1f2491d2ecd07e 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -40,8 +40,11 @@ temp_show(struct device *dev, struct device_attribute *attr, char *buf)

 	ret = thermal_zone_get_temp(tz, &temperature);

-	if (ret)
+	if (ret) {
+		if (ret == -EAGAIN)
+			return -ENODATA;
 		return ret;
+	}

 	return sprintf(buf, "%d\n", temperature);
 }

---
base-commit: a24588245776dafc227243a01bfbeb8a59bafba9
change-id: 20250409-temp-6ebd13ad0dbd

Best regards,
-- 
Hsin-Te Yuan <yuanhsinte@...omium.org>