usb: gadget: f_fs: Add support for IPC logging

Log function entry and exit and dump relevant values
into IPC log buffer. This allows to debug various
race conditions and stability issues.

Allow this to be enabled with CONFIG_USB_F_FS_IPC_LOGGING
which is dependent on CONFIG_QGKI.

Change-Id: I15011d79fc2f054e64f8bbd1f8f5db8944b46ada
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>

drivers/usb/gadget/Kconfig

@@ -237,6 +237,18 @@ config USB_F_CDEV
 config USB_F_GSI
 	tristate
 
+config USB_F_FS_IPC_LOGGING
+	bool "Enable IPC logging for FunctionFS"
+	depends on QGKI
+	default IPC_LOGGING
+	help
+	  Enables additional debug messages in FunctionFS driver to be
+	  output via IPC Logging mechanism. This can be useful when
+	  troubleshooting transfer stalls or other general failures and
+	  determine if the issue is in the kernel gadget or the userspace
+	  client. Separate IPC log contexts are created for each function
+	  instance at mount time.
+
 # this first set of drivers all depend on bulk-capable hardware.
 
 config USB_CONFIGFS

drivers/usb/gadget/function/u_fs.h

@@ -18,6 +18,7 @@
 #include <linux/mutex.h>
 #include <linux/workqueue.h>
 #include <linux/refcount.h>
+#include <linux/ipc_logging.h>
 
 #ifdef VERBOSE_DEBUG
 #ifndef pr_vdebug
@@ -285,6 +286,9 @@ struct ffs_data {
 	 * destroyed by ffs_epfiles_destroy().
 	 */
 	struct ffs_epfile		*epfiles;
+#ifdef CONFIG_USB_F_FS_IPC_LOGGING
+	void				*ipc_log;
+#endif
 };