PM: Add sysfs attr for rechecking dev hash from PM trace

If the device which fails to resume is part of a loadable kernel module
it won't be checked at startup against the magic number stored in the
RTC.

Add a read-only sysfs attribute /sys/power/pm_trace_dev_match which
contains a list of newline separated devices (usually just the one)
which currently match the last magic number. This allows the device
which is failing to resume to be found after the modules are loaded
again.

Signed-off-by: James Hogan <james@albanarts.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 18 insertions, 0 deletions

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 6b12a0cf4d9f..7b5db6a8561e 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -281,12 +281,30 @@ pm_trace_store(struct kobject *kobj, struct kobj_attribute *attr,
 }
 
 power_attr(pm_trace);
+
+static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
+                                       struct kobj_attribute *attr,
+                                       char *buf)
+{
+        return show_trace_dev_match(buf, PAGE_SIZE);
+}
+
+static ssize_t
+pm_trace_dev_match_store(struct kobject *kobj, struct kobj_attribute *attr,
+                         const char *buf, size_t n)
+{
+        return -EINVAL;
+}
+
+power_attr(pm_trace_dev_match);
+
 #endif /* CONFIG_PM_TRACE */
 
 static struct attribute * g[] = {
         &state_attr.attr,
 #ifdef CONFIG_PM_TRACE
         &pm_trace_attr.attr,
+        &pm_trace_dev_match_attr.attr,
 #endif
 #ifdef CONFIG_PM_SLEEP
         &pm_async_attr.attr,