[PATCH v4] scsi: add debugfs directories

[Douglas Gilbert <dgilbert@xxxxxxxxxxxx>]

Add a top level "scsi" directory in debugfs (usually at 
/sys/kernel/debugfs/scsi) with two subdirectories: "uld" and "lld".
The idea is to place mid-level related 'knobs' in the "scsi"
directory, and for the ULDs to make subsirectories like
"scsi/uld/sd" and "scsi/uld/st" as required. LLDs could follow a
similar pattern.

Changes since v3:
  - re-arrange as per scsi netlink interface [James Bottomley]
  - make all debugfs code conditional on CONFIG_BLK_DEBUG_FS

Changes since v2:
  - export symbols so other driver can use them [John Garry]
  - make prior code conditional on CONFIG_BLK_DEBUG_FS

Changes since v1:
  - tweak Makefile to keep kbuild test robot happier

Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---

My intention is to add a /sys/kernel/debug/scsi/uld/sg
directory containing at least a pseudo file called debug to have
the same actions as /proc/scsi/sg/debug , as part of my v4
patchset.

 drivers/scsi/scsi.c         |  3 +++
 drivers/scsi/scsi_debugfs.c | 33 ++++++++++++++++++++++++++++++++-
 drivers/scsi/scsi_priv.h    | 12 ++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index fc1356d101b0..e8676a19ba6e 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -812,6 +812,8 @@ static int __init init_scsi(void)
 
 	scsi_netlink_init();
 
+	scsi_debugfs_init();
+
 	printk(KERN_NOTICE "SCSI subsystem initialized\n");
 	return 0;
 
@@ -832,6 +834,7 @@ static int __init init_scsi(void)
 
 static void __exit exit_scsi(void)
 {
+	scsi_debugfs_exit();
 	scsi_netlink_exit();
 	scsi_sysfs_unregister();
 	scsi_exit_sysctl();
diff --git a/drivers/scsi/scsi_debugfs.c b/drivers/scsi/scsi_debugfs.c
index c5a8756384bc..20d4cb0fa58b 100644
--- a/drivers/scsi/scsi_debugfs.c
+++ b/drivers/scsi/scsi_debugfs.c
@@ -1,8 +1,18 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/seq_file.h>
+#include <linux/debugfs.h>
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_dbg.h>
-#include "scsi_debugfs.h"
+#include "scsi_priv.h"
+
+struct dentry *scsi_debugfs_root;
+struct dentry *scsi_debugfs_uld;
+struct dentry *scsi_debugfs_lld;
+
+EXPORT_SYMBOL(scsi_debugfs_root);
+EXPORT_SYMBOL(scsi_debugfs_uld);
+EXPORT_SYMBOL(scsi_debugfs_lld);
+
 
 #define SCSI_CMD_FLAG_NAME(name)[const_ilog2(SCMD_##name)] = #name
 static const char *const scsi_cmd_flags[] = {
@@ -50,3 +60,24 @@ void scsi_show_rq(struct seq_file *m, struct request *rq)
 		   timeout_ms / 1000, timeout_ms % 1000,
 		   alloc_ms / 1000, alloc_ms % 1000);
 }
+
+void scsi_debugfs_init(void)
+{
+        scsi_debugfs_root = debugfs_create_dir("scsi", NULL);
+        if (!scsi_debugfs_root)
+                return;
+        scsi_debugfs_uld = debugfs_create_dir("uld", scsi_debugfs_root);
+        if (!scsi_debugfs_uld) {
+		scsi_debugfs_exit();
+		return;
+	}
+        scsi_debugfs_lld = debugfs_create_dir("lld", scsi_debugfs_root);
+        if (!scsi_debugfs_lld)
+                scsi_debugfs_exit();
+}
+
+void scsi_debugfs_exit(void)
+{
+	if (scsi_debugfs_root)
+		debugfs_remove_recursive(scsi_debugfs_root);
+}
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 99f1db5e467e..e24835e8fa4f 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -160,6 +160,18 @@ static inline void scsi_netlink_init(void) {}
 static inline void scsi_netlink_exit(void) {}
 #endif
 
+/* scsi_debugfs.c */
+#ifdef CONFIG_BLK_DEBUG_FS
+extern void scsi_debugfs_init(void);
+extern void scsi_debugfs_exit(void);
+extern struct dentry *scsi_debugfs_root;
+extern struct dentry *scsi_debugfs_uld;
+extern struct dentry *scsi_debugfs_lld;
+#else
+static inline void scsi_debugfs_init(void) {}
+static inline void scsi_debugfs_exit(void) {}
+#endif
+
 /* scsi_pm.c */
 #ifdef CONFIG_PM
 extern const struct dev_pm_ops scsi_bus_pm_ops;
-- 
2.17.1