Allow EAGAIN failures
Certain devices are known to return EAGAIN failures when read
too frequently, so be tolerant of them.
On startup, the code will retry for up to a second to get a good
first reading, and then in the main loop the code will just stick
with the current value if it fails that way.
Resolves openbmc/openbmc#2038
Change-Id: I7621aa30429c43276239982a03ec3eef02ce9c6e
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/sysfs.hpp b/sysfs.hpp
index ada73e8..b4709eb 100644
--- a/sysfs.hpp
+++ b/sysfs.hpp
@@ -1,10 +1,29 @@
#pragma once
+#include <exception>
#include <fstream>
#include <string>
namespace sysfs {
+/**
+ * @class DeviceBusyException
+ *
+ * An internal exception which will be thrown when
+ * readSysfsWithCallout() hits an EAGAIN. Will never bubble
+ * up to terminate the application, nor does it need to be
+ * reported.
+ */
+class DeviceBusyException : public std::runtime_error
+{
+ public:
+
+ DeviceBusyException(const std::string& path) :
+ std::runtime_error(path + " busy")
+ {
+ }
+};
+
inline std::string make_sysfs_path(const std::string& path,
const std::string& type,
const std::string& id,
@@ -37,6 +56,8 @@
* @param[in] type - The hwmon type (ex. temp).
* @param[in] id - The hwmon id (ex. 1).
* @param[in] sensor - The hwmon sensor (ex. input).
+ * @param[in] throwDeviceBusy - will throw a DeviceBusyException
+ * on an EAGAIN errno instead of an error log exception.
*
* @returns - The read value.
*/
@@ -44,7 +65,8 @@
const std::string& instance,
const std::string& type,
const std::string& id,
- const std::string& sensor);
+ const std::string& sensor,
+ bool throwDeviceBusy = true);
/** @brief Write a hwmon sysfs value
*