From e90a4edb7e6aceb0880cf1fa79647d7f75ec57d9 Mon Sep 17 00:00:00 2001 From: Hsin-Te Yuan Date: Fri, 20 Jun 2025 10:41:43 +0000 Subject: [PATCH] thermal: sysfs: Return ENODATA instead of EAGAIN for reads [ Upstream commit 1a4aabc27e95674837f2e25f4ef340c0469e6203 ] According to POSIX spec, EAGAIN returned by read with O_NONBLOCK set means the read would block. Hence, the common implementation in nonblocking model will poll the file when the nonblocking read returns EAGAIN. However, when the target file is thermal zone, this mechanism will totally malfunction because thermal zone doesn't implement sysfs notification and thus the poll will never return. For example, the read in Golang implemnts such method and sometimes hangs at reading some thermal zones via sysfs. Change to return -ENODATA instead of -EAGAIN to userspace. Signed-off-by: Hsin-Te Yuan Link: https://patch.msgid.link/20250620-temp-v3-1-6becc6aeb66c@chromium.org Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin --- drivers/thermal/thermal_sysfs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c index 1838aa729bb50..c58c53d4ecc66 100644 --- a/drivers/thermal/thermal_sysfs.c +++ b/drivers/thermal/thermal_sysfs.c @@ -40,10 +40,13 @@ temp_show(struct device *dev, struct device_attribute *attr, char *buf) ret = thermal_zone_get_temp(tz, &temperature); - if (ret) - return ret; + if (!ret) + return sprintf(buf, "%d\n", temperature); - return sprintf(buf, "%d\n", temperature); + if (ret == -EAGAIN) + return -ENODATA; + + return ret; } static ssize_t -- 2.47.3