HID: use debugfs for report dumping descriptor

It is a little bit inconvenient for people who have some non-standard
HID hardware (usually violating the HID specification) to have to
recompile kernel with CONFIG_HID_DEBUG to be able to see kernel's perspective
of the HID report descriptor and observe the parsed events. Plus the messages
are then mixed up inconveniently with the rest of the dmesg stuff.

This patch implements /sys/kernel/debug/hid/<device>/rdesc file, which
represents the kernel's view of report descriptor (both the raw report
descriptor data and parsed contents).

With all the device-specific debug data being available through debugfs, there
is no need for keeping CONFIG_HID_DEBUG, as the 'debug' parameter to the
hid module will now only output only driver-specific debugging options, which has
absolutely minimal memory footprint, just a few error messages and one global
flag (hid_debug).

We use the current set of output formatting functions. The ones that need to be
used both for one-shot rdesc seq_file and also for continuous flow of data
(individual reports, as being sent by the device) distinguish according to the
passed seq_file parameter, and if it is NULL, it still output to kernel ringbuffer,
otherwise the corresponding seq_file is used for output.

The format of the output is preserved.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

2 files changed, 23 insertions, 13 deletions

diff --git a/include/linux/hid-debug.h b/include/linux/hid-debug.h
index 50d568ec178a..516e12c33235 100644
--- a/include/linux/hid-debug.h
+++ b/include/linux/hid-debug.h
@@ -2,7 +2,7 @@
 #define __HID_DEBUG_H
 
 /*
- *  Copyright (c) 2007	Jiri Kosina
+ *  Copyright (c) 2007-2009	Jiri Kosina
  */
 
 /*
@@ -22,24 +22,30 @@
  *
  */
 
-#ifdef CONFIG_HID_DEBUG
+#ifdef CONFIG_DEBUG_FS
 
 void hid_dump_input(struct hid_usage *, __s32);
-void hid_dump_device(struct hid_device *);
-void hid_dump_field(struct hid_field *, int);
-void hid_resolv_usage(unsigned);
-void hid_resolv_event(__u8, __u16);
+void hid_dump_device(struct hid_device *, struct seq_file *);
+void hid_dump_field(struct hid_field *, int, struct seq_file *);
+void hid_resolv_usage(unsigned, struct seq_file *);
+void hid_debug_register(struct hid_device *, const char *);
+void hid_debug_unregister(struct hid_device *);
+void hid_debug_init(void);
+void hid_debug_exit(void);
 
 #else
 
-#define hid_dump_input(a,b)     do { } while (0)
-#define hid_dump_device(c)      do { } while (0)
-#define hid_dump_field(a,b)     do { } while (0)
-#define hid_resolv_usage(a)         do { } while (0)
-#define hid_resolv_event(a,b)       do { } while (0)
-
-#endif /* CONFIG_HID_DEBUG */
+#define hid_dump_input(a,b)		do { } while (0)
+#define hid_dump_device(c)		do { } while (0)
+#define hid_dump_field(a,b)		do { } while (0)
+#define hid_resolv_usage(a)		do { } while (0)
+#define hid_resolv_event(a,b)		do { } while (0)
+#define hid_debug_register(a, b)	do { } while (0)
+#define hid_debug_unregister(a)		do { } while (0)
+#define hid_debug_init()		do { } while (0)
+#define hid_debug_exit()		do { } while (0)
 
+#endif
 
 #endif
 
diff --git a/include/linux/hid.h b/include/linux/hid.h
index a72876e43589..da09ab140ef1 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -451,6 +451,10 @@ struct hid_device {							/* device report descriptor */
 	char phys[64];							/* Device physical location */
 	char uniq[64];							/* Device unique identifier (serial #) */
 
+	/* debugfs */
+	struct dentry *debug_dir;
+	struct dentry *debug_rdesc;
+
 	void *driver_data;
 
 	/* temporary hid_ff handling (until moved to the drivers) */