[PATCH for-5.7/drivers v2 1/1] null_blk: describe the usage of fault injection param

[Dongli Zhang <dongli.zhang@oracle.com>]

As null_blk is a very good start point to test block layer, this patch
adds description and comments to 'timeout', 'requeue' and 'init_hctx' to
explain how to use fault injection with null_blk.

The nvme has similar with nvme_core.fail_request in the form of comment.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
Changed since v1:
  - rebase at for-5.7/drivers
  - describe 'init_hctx' as well

 drivers/block/null_blk_main.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 8060ffa4bc75..b324cc5fcaf7 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -97,14 +97,21 @@ module_param_named(home_node, g_home_node, int, 0444);
 MODULE_PARM_DESC(home_node, "Home node for the device");
 
 #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
+/*
+ * For more details about fault injection, please refer to
+ * Documentation/fault-injection/fault-injection.rst.
+ */
 static char g_timeout_str[80];
 module_param_string(timeout, g_timeout_str, sizeof(g_timeout_str), 0444);
+MODULE_PARM_DESC(timeout, "Fault injection. timeout=<interval>,<probability>,<space>,<times>");
 
 static char g_requeue_str[80];
 module_param_string(requeue, g_requeue_str, sizeof(g_requeue_str), 0444);
+MODULE_PARM_DESC(requeue, "Fault injection. requeue=<interval>,<probability>,<space>,<times>");
 
 static char g_init_hctx_str[80];
 module_param_string(init_hctx, g_init_hctx_str, sizeof(g_init_hctx_str), 0444);
+MODULE_PARM_DESC(init_hctx, "Fault injection to fail hctx init. init_hctx=<interval>,<probability>,<space>,<times>");
 #endif
 
 static int g_queue_mode = NULL_Q_MQ;
-- 
2.17.1