[PATCH v7 3/3] HID: input: Add support for multiple batteries per device

[Lucas Zampieri <lcasmz54@gmail.com>]

Add support for HID devices that report multiple batteries, each
identified by its report ID.

The hid_device->battery pointer is replaced with a batteries list.
Batteries are named using the pattern hid-{uniq}-battery-{report_id}.
The hid_get_battery() helper returns the first battery in the list for
backwards compatibility with single-battery drivers.

Signed-off-by: Lucas Zampieri <lcasmz54@gmail.com>
---
 drivers/hid/hid-core.c  |  4 ++++
 drivers/hid/hid-input.c | 44 ++++++++++++++++++++++++++++-------------
 include/linux/hid.h     | 11 ++++++++---
 3 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index da57cbf0a..58a31ee07 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2995,6 +2995,10 @@ struct hid_device *hid_allocate_device(void)
 	mutex_init(&hdev->ll_open_lock);
 	kref_init(&hdev->ref);
 
+#ifdef CONFIG_HID_BATTERY_STRENGTH
+	INIT_LIST_HEAD(&hdev->batteries);
+#endif
+
 	ret = hid_bpf_device_init(hdev);
 	if (ret)
 		goto out_err;
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index b5d34658b..8fff185fe 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -507,6 +507,18 @@ static int hidinput_get_battery_property(struct power_supply *psy,
 	return ret;
 }
 
+static struct hid_battery *hidinput_find_battery(struct hid_device *dev,
+						 int report_id)
+{
+	struct hid_battery *bat;
+
+	list_for_each_entry(bat, &dev->batteries, list) {
+		if (bat->report_id == report_id)
+			return bat;
+	}
+	return NULL;
+}
+
 static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 				  struct hid_field *field, bool is_percentage)
 {
@@ -517,13 +529,15 @@ static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	s32 min, max;
 	int error;
 
-	if (dev->battery)
-		return 0;	/* already initialized? */
+	/* Check if battery for this report ID already exists */
+	if (hidinput_find_battery(dev, field->report->id))
+		return 0;
 
 	quirks = find_battery_quirk(dev);
 
-	hid_dbg(dev, "device %x:%x:%x %d quirks %d\n",
-		dev->bus, dev->vendor, dev->product, dev->version, quirks);
+	hid_dbg(dev, "device %x:%x:%x %d quirks %d report_id %d\n",
+		dev->bus, dev->vendor, dev->product, dev->version, quirks,
+		field->report->id);
 
 	if (quirks & HID_BATTERY_QUIRK_IGNORE)
 		return 0;
@@ -538,9 +552,11 @@ static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 		goto err_free_bat;
 	}
 
-	psy_desc->name = devm_kasprintf(&dev->dev, GFP_KERNEL, "hid-%s-battery",
+	psy_desc->name = devm_kasprintf(&dev->dev, GFP_KERNEL,
+					"hid-%s-battery-%d",
 					strlen(dev->uniq) ?
-						dev->uniq : dev_name(&dev->dev));
+						dev->uniq : dev_name(&dev->dev),
+					field->report->id);
 	if (!psy_desc->name) {
 		error = -ENOMEM;
 		goto err_free_desc;
@@ -593,7 +609,7 @@ static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	}
 
 	power_supply_powers(bat->ps, &dev->dev);
-	dev->battery = bat;
+	list_add_tail(&bat->list, &dev->batteries);
 	return 0;
 
 err_free_name:
@@ -602,7 +618,6 @@ static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	devm_kfree(&dev->dev, psy_desc);
 err_free_bat:
 	devm_kfree(&dev->dev, bat);
-	dev->battery = NULL;
 	return error;
 }
 
@@ -620,12 +635,13 @@ static bool hidinput_update_battery_charge_status(struct hid_battery *bat,
 	return false;
 }
 
-static void hidinput_update_battery(struct hid_device *dev, unsigned int usage,
-				    int value)
+static void hidinput_update_battery(struct hid_device *dev, int report_id,
+				    unsigned int usage, int value)
 {
-	struct hid_battery *bat = dev->battery;
+	struct hid_battery *bat;
 	int capacity;
 
+	bat = hidinput_find_battery(dev, report_id);
 	if (!bat)
 		return;
 
@@ -661,8 +677,8 @@ static int hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	return 0;
 }
 
-static void hidinput_update_battery(struct hid_device *dev, unsigned int usage,
-				    int value)
+static void hidinput_update_battery(struct hid_device *dev, int report_id,
+				    unsigned int usage, int value)
 {
 }
 #endif	/* CONFIG_HID_BATTERY_STRENGTH */
@@ -1546,7 +1562,7 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
 		return;
 
 	if (usage->type == EV_PWR) {
-		hidinput_update_battery(hid, usage->hid, value);
+		hidinput_update_battery(hid, report->id, usage->hid, value);
 		return;
 	}
 
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 71beff003..442a80d79 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -648,6 +648,7 @@ enum hid_battery_status {
  * @avoid_query: if true, avoid querying battery (e.g., for stylus)
  * @present: if true, battery is present (may be dynamic)
  * @ratelimit_time: rate limiting for battery reports
+ * @list: list node for linking into hid_device's battery list
  */
 struct hid_battery {
 	struct hid_device *dev;
@@ -662,6 +663,7 @@ struct hid_battery {
 	bool avoid_query;
 	bool present;
 	ktime_t ratelimit_time;
+	struct list_head list;
 };
 
 struct hid_driver;
@@ -700,9 +702,10 @@ struct hid_device {
 #ifdef CONFIG_HID_BATTERY_STRENGTH
 	/*
 	 * Power supply information for HID devices which report
-	 * battery strength. battery is non-NULL if successfully registered.
+	 * battery strength. Each battery is tracked separately in the
+	 * batteries list.
 	 */
-	struct hid_battery *battery;
+	struct list_head batteries;
 #endif
 
 	unsigned long status;						/* see STAT flags above */
@@ -767,7 +770,9 @@ static inline void hid_set_drvdata(struct hid_device *hdev, void *data)
 #ifdef CONFIG_HID_BATTERY_STRENGTH
 static inline struct hid_battery *hid_get_battery(struct hid_device *hdev)
 {
-	return hdev->battery;
+	if (list_empty(&hdev->batteries))
+		return NULL;
+	return list_first_entry(&hdev->batteries, struct hid_battery, list);
 }
 #endif
 
-- 
2.53.0