dell-laptop: Add debugfs support

Export the status of RF killswitch through debugfs.

The killswitch status is obtained by the SMI to BIOS. Exporting this status
through debugfs can help identify the issue with the misbehaving firmware.
Signed-off-by: Keng-Yu Lin <keng-yu.lin@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/dell-laptop.c

@@ -25,6 +25,8 @@
 #include <linux/mm.h>
 #include <linux/i8042.h>
 #include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 #include "../../firmware/dcdbas.h"
 
 #define BRIGHTNESS_TOKEN 0x7d
@@ -325,6 +327,75 @@ static const struct rfkill_ops dell_rfkill_ops = {
 	.query = dell_rfkill_query,
 };
 
+static struct dentry *dell_laptop_dir;
+
+static int dell_debugfs_show(struct seq_file *s, void *data)
+{
+	int status;
+
+	get_buffer();
+	dell_send_request(buffer, 17, 11);
+	status = buffer->output[1];
+	release_buffer();
+
+	seq_printf(s, "status:\t0x%X\n", status);
+	seq_printf(s, "Bit 0 : Hardware switch supported:   %lu\n",
+		   status & BIT(0));
+	seq_printf(s, "Bit 1 : Wifi locator supported:      %lu\n",
+		  (status & BIT(1)) >> 1);
+	seq_printf(s, "Bit 2 : Wifi is supported:           %lu\n",
+		  (status & BIT(2)) >> 2);
+	seq_printf(s, "Bit 3 : Bluetooth is supported:      %lu\n",
+		  (status & BIT(3)) >> 3);
+	seq_printf(s, "Bit 4 : WWAN is supported:           %lu\n",
+		  (status & BIT(4)) >> 4);
+	seq_printf(s, "Bit 5 : Wireless keyboard supported: %lu\n",
+		  (status & BIT(5)) >> 5);
+	seq_printf(s, "Bit 8 : Wifi is installed:           %lu\n",
+		  (status & BIT(8)) >> 8);
+	seq_printf(s, "Bit 9 : Bluetooth is installed:      %lu\n",
+		  (status & BIT(9)) >> 9);
+	seq_printf(s, "Bit 10: WWAN is installed:           %lu\n",
+		  (status & BIT(10)) >> 10);
+	seq_printf(s, "Bit 16: Hardware switch is on:       %lu\n",
+		  (status & BIT(16)) >> 16);
+	seq_printf(s, "Bit 17: Wifi is blocked:             %lu\n",
+		  (status & BIT(17)) >> 17);
+	seq_printf(s, "Bit 18: Bluetooth is blocked:        %lu\n",
+		  (status & BIT(18)) >> 18);
+	seq_printf(s, "Bit 19: WWAN is blocked:             %lu\n",
+		  (status & BIT(19)) >> 19);
+
+	seq_printf(s, "\nhwswitch_state:\t0x%X\n", hwswitch_state);
+	seq_printf(s, "Bit 0 : Wifi controlled by switch:      %lu\n",
+		   hwswitch_state & BIT(0));
+	seq_printf(s, "Bit 1 : Bluetooth controlled by switch: %lu\n",
+		   (hwswitch_state & BIT(1)) >> 1);
+	seq_printf(s, "Bit 2 : WWAN controlled by switch:      %lu\n",
+		   (hwswitch_state & BIT(2)) >> 2);
+	seq_printf(s, "Bit 7 : Wireless switch config locked:  %lu\n",
+		   (hwswitch_state & BIT(7)) >> 7);
+	seq_printf(s, "Bit 8 : Wifi locator enabled:           %lu\n",
+		   (hwswitch_state & BIT(8)) >> 8);
+	seq_printf(s, "Bit 15: Wifi locator setting locked:    %lu\n",
+		   (hwswitch_state & BIT(15)) >> 15);
+
+	return 0;
+}
+
+static int dell_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, dell_debugfs_show, inode->i_private);
+}
+
+static const struct file_operations dell_debugfs_fops = {
+	.owner = THIS_MODULE,
+	.open = dell_debugfs_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
 static void dell_update_rfkill(struct work_struct *ignored)
 {
 	if (wifi_rfkill)
@@ -556,6 +627,11 @@ static int __init dell_init(void)
 		goto fail_filter;
 	}
 
+	dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL);
+	if (dell_laptop_dir != NULL)
+		debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL,
+				    &dell_debugfs_fops);
+
 #ifdef CONFIG_ACPI
 	/* In the event of an ACPI backlight being available, don't
 	 * register the platform controller.
@@ -615,6 +691,7 @@ static int __init dell_init(void)
 
 static void __exit dell_exit(void)
 {
+	debugfs_remove_recursive(dell_laptop_dir);
 	i8042_remove_filter(dell_laptop_i8042_filter);
 	cancel_delayed_work_sync(&dell_rfkill_work);
 	backlight_device_unregister(dell_backlight_device);