ACPI, cpuidle: Clarify C-state description in sysfs

Add a new sysfs entry under cpuidle states. desc - can be used by driver to
communicate to userspace any specific information about the state.
This helps in identifying the exact hardware C-states behind the ACPI C-state
definition.

Idea is to export this through powertop, which will help to map the C-state
reported by powertop to actual hardware C-state.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 088ea74edd34..69102ca05685 100644
--- a/drivers/cpuidle/sysfs.c
+++ b/drivers/cpuidle/sysfs.c
@@ -218,16 +218,23 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, char *buf) \
         return sprintf(buf, "%u\n", state->_name);\
 }
 
-static ssize_t show_state_name(struct cpuidle_state *state, char *buf)
-{
-        return sprintf(buf, "%s\n", state->name);
+#define define_show_state_str_function(_name) \
+static ssize_t show_state_##_name(struct cpuidle_state *state, char *buf) \
+{ \
+        if (state->_name[0] == '\0')\
+                return sprintf(buf, "<null>\n");\
+        return sprintf(buf, "%s\n", state->_name);\
 }
 
 define_show_state_function(exit_latency)
 define_show_state_function(power_usage)
 define_show_state_function(usage)
 define_show_state_function(time)
+define_show_state_str_function(name)
+define_show_state_str_function(desc)
+
 define_one_state_ro(name, show_state_name);
+define_one_state_ro(desc, show_state_desc);
 define_one_state_ro(latency, show_state_exit_latency);
 define_one_state_ro(power, show_state_power_usage);
 define_one_state_ro(usage, show_state_usage);
@@ -235,6 +242,7 @@ define_one_state_ro(time, show_state_time);
 
 static struct attribute *cpuidle_state_default_attrs[] = {
         &attr_name.attr,
+        &attr_desc.attr,
         &attr_latency.attr,
         &attr_power.attr,
         &attr_usage.attr,