HID: add backlight support to PicoLCD device

Add backlight support to PicoLCD device.

Backlight support depends on backlight class and is only being
compiled if backlight class has been selected.
Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/Kconfig

@@ -278,8 +278,8 @@ config HID_PICOLCD
 	  - Keypad
 	  - Switching between Firmware and Flash mode
 	  - Framebuffer for monochrome 256x64 display
+	  - Backlight control    (needs CONFIG_BACKLIGHT_CLASS_DEVICE)
 	  Features that are not (yet) supported:
-	  - Backlight control
 	  - Contrast control
 	  - IR
 	  - General purpose outputs

drivers/hid/hid-picolcd.c

@@ -26,6 +26,7 @@
 
 #include <linux/fb.h>
 #include <linux/vmalloc.h>
+#include <linux/backlight.h>
 
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
@@ -183,6 +184,11 @@ struct picolcd_data {
 	struct fb_info *fb_info;
 	struct fb_deferred_io fb_defio;
 #endif /* CONFIG_FB */
+#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) || defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE)
+	struct backlight_device *backlight;
+	u8 lcd_brightness;
+	u8 lcd_power;
+#endif /* CONFIG_BACKLIGHT_CLASS_DEVICE */
 
 	/* Housekeeping stuff */
 	spinlock_t lock;
@@ -729,7 +735,7 @@ static void picolcd_exit_framebuffer(struct picolcd_data *data)
 	kfree(fb_vbitmap);
 }
 
-
+#define picolcd_fbinfo(d) ((d)->fb_info)
 #else
 static inline int picolcd_fb_reset(struct picolcd_data *data, int clear)
 {
@@ -742,8 +748,107 @@ static inline int picolcd_init_framebuffer(struct picolcd_data *data)
 static void picolcd_exit_framebuffer(struct picolcd_data *data)
 {
 }
+#define picolcd_fbinfo(d) NULL
 #endif /* CONFIG_FB */
 
+#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) || defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE)
+/*
+ * backlight class device
+ */
+static int picolcd_get_brightness(struct backlight_device *bdev)
+{
+	struct picolcd_data *data = bl_get_data(bdev);
+	return data->lcd_brightness;
+}
+
+static int picolcd_set_brightness(struct backlight_device *bdev)
+{
+	struct picolcd_data *data = bl_get_data(bdev);
+	struct hid_report *report = picolcd_out_report(REPORT_BRIGHTNESS, data->hdev);
+	unsigned long flags;
+
+	if (!report || report->maxfield != 1 || report->field[0]->report_count != 1)
+		return -ENODEV;
+
+	data->lcd_brightness = bdev->props.brightness & 0x0ff;
+	data->lcd_power      = bdev->props.power;
+	spin_lock_irqsave(&data->lock, flags);
+	hid_set_field(report->field[0], 0, data->lcd_power == FB_BLANK_UNBLANK ? data->lcd_brightness : 0);
+	usbhid_submit_report(data->hdev, report, USB_DIR_OUT);
+	spin_unlock_irqrestore(&data->lock, flags);
+	return 0;
+}
+
+static int picolcd_check_bl_fb(struct backlight_device *bdev, struct fb_info *fb)
+{
+	return fb && fb == picolcd_fbinfo((struct picolcd_data *)bl_get_data(bdev));
+}
+
+static const struct backlight_ops picolcd_blops = {
+	.update_status  = picolcd_set_brightness,
+	.get_brightness = picolcd_get_brightness,
+	.check_fb       = picolcd_check_bl_fb,
+};
+
+static int picolcd_init_backlight(struct picolcd_data *data, struct hid_report *report)
+{
+	struct device *dev = &data->hdev->dev;
+	struct backlight_device *bdev;
+	struct backlight_properties props;
+	if (!report)
+		return -ENODEV;
+	if (report->maxfield != 1 || report->field[0]->report_count != 1 ||
+			report->field[0]->report_size != 8) {
+		dev_err(dev, "unsupported BRIGHTNESS report");
+		return -EINVAL;
+	}
+
+	memset(&props, 0, sizeof(props));
+	props.max_brightness = 0xff;
+	bdev = backlight_device_register(dev_name(dev), dev, data,
+			&picolcd_blops, &props);
+	if (IS_ERR(bdev)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bdev);
+	}
+	bdev->props.brightness     = 0xff;
+	data->lcd_brightness       = 0xff;
+	data->backlight            = bdev;
+	picolcd_set_brightness(bdev);
+	return 0;
+}
+
+static void picolcd_exit_backlight(struct picolcd_data *data)
+{
+	struct backlight_device *bdev = data->backlight;
+
+	data->backlight = NULL;
+	if (bdev)
+		backlight_device_unregister(bdev);
+}
+
+static inline int picolcd_resume_backlight(struct picolcd_data *data)
+{
+	if (!data->backlight)
+		return 0;
+	return picolcd_set_brightness(data->backlight);
+}
+
+#else
+static inline int picolcd_init_backlight(struct picolcd_data *data,
+		struct hid_report *report)
+{
+	return 0;
+}
+static inline void picolcd_exit_backlight(struct picolcd_data *data)
+{
+}
+static inline int picolcd_resume_backlight(struct picolcd_data *data)
+{
+	return 0;
+}
+#endif /* CONFIG_BACKLIGHT_CLASS_DEVICE */
+
 /*
  * input class device
  */
@@ -879,6 +984,7 @@ static int picolcd_reset(struct hid_device *hdev)
 	if (error)
 		return error;
 
+	picolcd_resume_backlight(data);
 #if defined(CONFIG_FB) || defined(CONFIG_FB_MODULE)
 	if (data->fb_info)
 		schedule_delayed_work(&data->fb_info->deferred_work, 0);
@@ -1567,6 +1673,11 @@ static int picolcd_probe_lcd(struct hid_device *hdev, struct picolcd_data *data)
 	if (error)
 		goto err;
 
+	/* Setup backlight class device */
+	error = picolcd_init_backlight(data, picolcd_out_report(REPORT_BRIGHTNESS, hdev));
+	if (error)
+		goto err;
+
 #ifdef CONFIG_DEBUG_FS
 	report = picolcd_out_report(REPORT_READ_MEMORY, hdev);
 	if (report && report->maxfield == 1 && report->field[0]->report_size == 8)
@@ -1576,6 +1687,7 @@ static int picolcd_probe_lcd(struct hid_device *hdev, struct picolcd_data *data)
 #endif
 	return 0;
 err:
+	picolcd_exit_backlight(data);
 	picolcd_exit_framebuffer(data);
 	picolcd_exit_cir(data);
 	picolcd_exit_keys(data);
@@ -1707,6 +1819,7 @@ static void picolcd_remove(struct hid_device *hdev)
 	spin_unlock_irqrestore(&data->lock, flags);
 
 	/* Clean up the framebuffer */
+	picolcd_exit_backlight(data);
 	picolcd_exit_framebuffer(data);
 	/* Cleanup input */
 	picolcd_exit_cir(data);