iwlwifi: disallow log_event access if interface down

'echo 1 > log_event' generates the bogus "MAC is in deep sleep"
or "Timeout waiting for hardware access" log messages when
the interface is down, we should just disallow accessing the
device through debugfs when it is down.

Signed-off-by: Richard A. Griffiths <richardx.a.griffiths@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/dvm/debugfs.c b/drivers/net/wireless/iwlwifi/dvm/debugfs.c
index 8a2d9e6..b0f125c 100644
--- a/drivers/net/wireless/iwlwifi/dvm/debugfs.c
+++ b/drivers/net/wireless/iwlwifi/dvm/debugfs.c
@@ -83,7 +83,7 @@
 #define DEBUGFS_READ_FILE_OPS(name)                                     \
 	DEBUGFS_READ_FUNC(name);                                        \
 static const struct file_operations iwl_dbgfs_##name##_ops = {          \
-	.read = iwl_dbgfs_##name##_read,                       		\
+	.read = iwl_dbgfs_##name##_read,				\
 	.open = simple_open,						\
 	.llseek = generic_file_llseek,					\
 };
@@ -2254,6 +2254,10 @@
 	char buf[8];
 	int buf_size;
 
+	/* check that the interface is up */
+	if (!iwl_is_ready(priv))
+		return -EAGAIN;
+
 	memset(buf, 0, sizeof(buf));
 	buf_size = min(count, sizeof(buf) -  1);
 	if (copy_from_user(buf, user_buf, buf_size))