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>

1 files changed, 156 insertions, 71 deletions

diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 47ac1a7d66e1..067e173aa3e4 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -1,9 +1,9 @@
 /*
  *  (c) 1999 Andreas Gal		<gal@cs.uni-magdeburg.de>
  *  (c) 2000-2001 Vojtech Pavlik	<vojtech@ucw.cz>
- *  (c) 2007 Jiri Kosina
+ *  (c) 2007-2009 Jiri Kosina
  *
- *  Some debug stuff for the HID parser.
+ *  HID debugging support
  */
 
 /*
@@ -26,9 +26,13 @@
  * Vojtech Pavlik, Simunkova 1594, Prague 8, 182 00 Czech Republic
  */
 
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 #include <linux/hid.h>
 #include <linux/hid-debug.h>
 
+static struct dentry *hid_debug_root;
+
 struct hid_usage_entry {
 	unsigned  page;
 	unsigned  usage;
@@ -331,72 +335,83 @@ static const struct hid_usage_entry hid_usage_table[] = {
   { 0, 0, NULL }
 };
 
-static void resolv_usage_page(unsigned page) {
+static void resolv_usage_page(unsigned page, struct seq_file *f) {
 	const struct hid_usage_entry *p;
 
 	for (p = hid_usage_table; p->description; p++)
 		if (p->page == page) {
-			printk("%s", p->description);
+			if (!f)
+				printk("%s", p->description);
+			else
+				seq_printf(f, "%s", p->description);
 			return;
 		}
-	printk("%04x", page);
+	if (!f)
+		printk("%04x", page);
+	else
+		seq_printf(f, "%04x", page);
 }
 
-void hid_resolv_usage(unsigned usage) {
+void hid_resolv_usage(unsigned usage, struct seq_file *f) {
 	const struct hid_usage_entry *p;
 
-	if (!hid_debug)
-		return;
-
-	resolv_usage_page(usage >> 16);
-	printk(".");
+	resolv_usage_page(usage >> 16, f);
+	if (!f)
+		printk(".");
+	else
+		seq_printf(f, ".");
 	for (p = hid_usage_table; p->description; p++)
 		if (p->page == (usage >> 16)) {
 			for(++p; p->description && p->usage != 0; p++)
 				if (p->usage == (usage & 0xffff)) {
-					printk("%s", p->description);
+					if (!f)
+						printk("%s", p->description);
+					else
+						seq_printf(f,
+							"%s",
+							p->description);
 					return;
 				}
 			break;
 		}
-	printk("%04x", usage & 0xffff);
+	if (!f)
+		printk("%04x", usage & 0xffff);
+	else
+		seq_printf(f, "%04x", usage & 0xffff);
 }
 EXPORT_SYMBOL_GPL(hid_resolv_usage);
 
-static void tab(int n) {
-	printk(KERN_DEBUG "%*s", n, "");
+static void tab(int n, struct seq_file *f) {
+	seq_printf(f, "%*s", n, "");
 }
 
-void hid_dump_field(struct hid_field *field, int n) {
+void hid_dump_field(struct hid_field *field, int n, struct seq_file *f) {
 	int j;
 
-	if (!hid_debug)
-		return;
-
 	if (field->physical) {
-		tab(n);
-		printk("Physical(");
-		hid_resolv_usage(field->physical); printk(")\n");
+		tab(n, f);
+		seq_printf(f, "Physical(");
+		hid_resolv_usage(field->physical, f); seq_printf(f, ")\n");
 	}
 	if (field->logical) {
-		tab(n);
-		printk("Logical(");
-		hid_resolv_usage(field->logical); printk(")\n");
+		tab(n, f);
+		seq_printf(f, "Logical(");
+		hid_resolv_usage(field->logical, f); seq_printf(f, ")\n");
 	}
-	tab(n); printk("Usage(%d)\n", field->maxusage);
+	tab(n, f); seq_printf(f, "Usage(%d)\n", field->maxusage);
 	for (j = 0; j < field->maxusage; j++) {
-		tab(n+2); hid_resolv_usage(field->usage[j].hid); printk("\n");
+		tab(n+2, f); hid_resolv_usage(field->usage[j].hid, f); seq_printf(f, "\n");
 	}
 	if (field->logical_minimum != field->logical_maximum) {
-		tab(n); printk("Logical Minimum(%d)\n", field->logical_minimum);
-		tab(n); printk("Logical Maximum(%d)\n", field->logical_maximum);
+		tab(n, f); seq_printf(f, "Logical Minimum(%d)\n", field->logical_minimum);
+		tab(n, f); seq_printf(f, "Logical Maximum(%d)\n", field->logical_maximum);
 	}
 	if (field->physical_minimum != field->physical_maximum) {
-		tab(n); printk("Physical Minimum(%d)\n", field->physical_minimum);
-		tab(n); printk("Physical Maximum(%d)\n", field->physical_maximum);
+		tab(n, f); seq_printf(f, "Physical Minimum(%d)\n", field->physical_minimum);
+		tab(n, f); seq_printf(f, "Physical Maximum(%d)\n", field->physical_maximum);
 	}
 	if (field->unit_exponent) {
-		tab(n); printk("Unit Exponent(%d)\n", field->unit_exponent);
+		tab(n, f); seq_printf(f, "Unit Exponent(%d)\n", field->unit_exponent);
 	}
 	if (field->unit) {
 		static const char *systems[5] = { "None", "SI Linear", "SI Rotation", "English Linear", "English Rotation" };
@@ -417,77 +432,75 @@ void hid_dump_field(struct hid_field *field, int n) {
 		data >>= 4;
 
 		if(sys > 4) {
-			tab(n); printk("Unit(Invalid)\n");
+			tab(n, f); seq_printf(f, "Unit(Invalid)\n");
 		}
 		else {
 			int earlier_unit = 0;
 
-			tab(n); printk("Unit(%s : ", systems[sys]);
+			tab(n, f); seq_printf(f, "Unit(%s : ", systems[sys]);
 
 			for (i=1 ; i<sizeof(__u32)*2 ; i++) {
 				char nibble = data & 0xf;
 				data >>= 4;
 				if (nibble != 0) {
 					if(earlier_unit++ > 0)
-						printk("*");
-					printk("%s", units[sys][i]);
+						seq_printf(f, "*");
+					seq_printf(f, "%s", units[sys][i]);
 					if(nibble != 1) {
 						/* This is a _signed_ nibble(!) */
 
 						int val = nibble & 0x7;
 						if(nibble & 0x08)
 							val = -((0x7 & ~val) +1);
-						printk("^%d", val);
+						seq_printf(f, "^%d", val);
 					}
 				}
 			}
-			printk(")\n");
+			seq_printf(f, ")\n");
 		}
 	}
-	tab(n); printk("Report Size(%u)\n", field->report_size);
-	tab(n); printk("Report Count(%u)\n", field->report_count);
-	tab(n); printk("Report Offset(%u)\n", field->report_offset);
+	tab(n, f); seq_printf(f, "Report Size(%u)\n", field->report_size);
+	tab(n, f); seq_printf(f, "Report Count(%u)\n", field->report_count);
+	tab(n, f); seq_printf(f, "Report Offset(%u)\n", field->report_offset);
 
-	tab(n); printk("Flags( ");
+	tab(n, f); seq_printf(f, "Flags( ");
 	j = field->flags;
-	printk("%s", HID_MAIN_ITEM_CONSTANT & j ? "Constant " : "");
-	printk("%s", HID_MAIN_ITEM_VARIABLE & j ? "Variable " : "Array ");
-	printk("%s", HID_MAIN_ITEM_RELATIVE & j ? "Relative " : "Absolute ");
-	printk("%s", HID_MAIN_ITEM_WRAP & j ? "Wrap " : "");
-	printk("%s", HID_MAIN_ITEM_NONLINEAR & j ? "NonLinear " : "");
-	printk("%s", HID_MAIN_ITEM_NO_PREFERRED & j ? "NoPreferredState " : "");
-	printk("%s", HID_MAIN_ITEM_NULL_STATE & j ? "NullState " : "");
-	printk("%s", HID_MAIN_ITEM_VOLATILE & j ? "Volatile " : "");
-	printk("%s", HID_MAIN_ITEM_BUFFERED_BYTE & j ? "BufferedByte " : "");
-	printk(")\n");
+	seq_printf(f, "%s", HID_MAIN_ITEM_CONSTANT & j ? "Constant " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_VARIABLE & j ? "Variable " : "Array ");
+	seq_printf(f, "%s", HID_MAIN_ITEM_RELATIVE & j ? "Relative " : "Absolute ");
+	seq_printf(f, "%s", HID_MAIN_ITEM_WRAP & j ? "Wrap " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_NONLINEAR & j ? "NonLinear " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_NO_PREFERRED & j ? "NoPreferredState " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_NULL_STATE & j ? "NullState " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_VOLATILE & j ? "Volatile " : "");
+	seq_printf(f, "%s", HID_MAIN_ITEM_BUFFERED_BYTE & j ? "BufferedByte " : "");
+	seq_printf(f, ")\n");
 }
 EXPORT_SYMBOL_GPL(hid_dump_field);
 
-void hid_dump_device(struct hid_device *device) {
+void hid_dump_device(struct hid_device *device, struct seq_file *f)
+{
 	struct hid_report_enum *report_enum;
 	struct hid_report *report;
 	struct list_head *list;
 	unsigned i,k;
 	static const char *table[] = {"INPUT", "OUTPUT", "FEATURE"};
 
-	if (!hid_debug)
-		return;
-
 	for (i = 0; i < HID_REPORT_TYPES; i++) {
 		report_enum = device->report_enum + i;
 		list = report_enum->report_list.next;
 		while (list != &report_enum->report_list) {
 			report = (struct hid_report *) list;
-			tab(2);
-			printk("%s", table[i]);
+			tab(2, f);
+			seq_printf(f, "%s", table[i]);
 			if (report->id)
-				printk("(%d)", report->id);
-			printk("[%s]", table[report->type]);
-			printk("\n");
+				seq_printf(f, "(%d)", report->id);
+			seq_printf(f, "[%s]", table[report->type]);
+			seq_printf(f, "\n");
 			for (k = 0; k < report->maxfield; k++) {
-				tab(4);
-				printk("Field(%d)\n", k);
-				hid_dump_field(report->field[k], 6);
+				tab(4, f);
+				seq_printf(f, "Field(%d)\n", k);
+				hid_dump_field(report->field[k], 6, f);
 			}
 			list = list->next;
 		}
@@ -500,7 +513,7 @@ void hid_dump_input(struct hid_usage *usage, __s32 value) {
 		return;
 
 	printk(KERN_DEBUG "hid-debug: input ");
-	hid_resolv_usage(usage->hid);
+	hid_resolv_usage(usage->hid, NULL);
 	printk(" = %d\n", value);
 }
 EXPORT_SYMBOL_GPL(hid_dump_input);
@@ -767,12 +780,84 @@ static const char **names[EV_MAX + 1] = {
 	[EV_SND] = sounds,			[EV_REP] = repeats,
 };
 
-void hid_resolv_event(__u8 type, __u16 code) {
-
-	if (!hid_debug)
-		return;
+void hid_resolv_event(__u8 type, __u16 code, struct seq_file *f) {
 
-	printk("%s.%s", events[type] ? events[type] : "?",
+	seq_printf(f, "%s.%s", events[type] ? events[type] : "?",
 		names[type] ? (names[type][code] ? names[type][code] : "?") : "?");
 }
-EXPORT_SYMBOL_GPL(hid_resolv_event);
+
+void hid_dump_input_mapping(struct hid_device *hid, struct seq_file *f)
+{
+	int i, j, k;
+	struct hid_report *report;
+	struct hid_usage *usage;
+
+	for (k = HID_INPUT_REPORT; k <= HID_OUTPUT_REPORT; k++) {
+		list_for_each_entry(report, &hid->report_enum[k].report_list, list) {
+			for (i = 0; i < report->maxfield; i++) {
+				for ( j = 0; j < report->field[i]->maxusage; j++) {
+					usage = report->field[i]->usage + j;
+					hid_resolv_usage(usage->hid, f);
+					seq_printf(f, " ---> ");
+					hid_resolv_event(usage->type, usage->code, f);
+					seq_printf(f, "\n");
+				}
+			}
+		}
+	}
+
+}
+
+static int hid_debug_rdesc_show(struct seq_file *f, void *p)
+{
+	struct hid_device *hdev = f->private;
+	int i;
+
+	/* dump HID report descriptor */
+	for (i = 0; i < hdev->rsize; i++)
+		seq_printf(f, "%02x ", hdev->rdesc[i]);
+	seq_printf(f, "\n\n");
+
+	/* dump parsed data and input mappings */
+	hid_dump_device(hdev, f);
+	seq_printf(f, "\n");
+	hid_dump_input_mapping(hdev, f);
+
+	return 0;
+}
+
+static int hid_debug_rdesc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, hid_debug_rdesc_show, inode->i_private);
+}
+
+static const struct file_operations hid_debug_rdesc_fops = {
+	.open           = hid_debug_rdesc_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+void hid_debug_register(struct hid_device *hdev, const char *name)
+{
+	hdev->debug_dir = debugfs_create_dir(name, hid_debug_root);
+	hdev->debug_rdesc = debugfs_create_file("rdesc", 0400,
+			hdev->debug_dir, hdev, &hid_debug_rdesc_fops);
+}
+
+void hid_debug_unregister(struct hid_device *hdev)
+{
+	debugfs_remove(hdev->debug_rdesc);
+	debugfs_remove(hdev->debug_dir);
+}
+
+void hid_debug_init(void)
+{
+	hid_debug_root = debugfs_create_dir("hid", NULL);
+}
+
+void hid_debug_exit(void)
+{
+	debugfs_remove_recursive(hid_debug_root);
+}
+