usb: misc: apple-mfi-fastcharge: Make power supply names unique

When multiple Apple devices are connected concurrently, the
apple-mfi-fastcharge driver fails to probe the subsequent devices with
the following error:

    sysfs: cannot create duplicate filename '/class/power_supply/apple_mfi_fastcharge'
    apple-mfi-fastcharge 5-2.4.3.3: probe of 5-2.4.3.3 failed with error -17

This happens because the driver uses a fixed power supply name
("apple_mfi_fastcharge") for all devices, causing a sysfs name
conflict when a second device is connected.

Fix this by generating unique names using the USB bus and device
number (e.g., "apple_mfi_fastcharge_5-12"). This ensures each
connected device gets a unique power supply entry in sysfs.

The change requires storing a copy of the power_supply_desc structure
in the per-device mfi_device struct, since the name pointer needs to
remain valid for the lifetime of the power supply registration.

Fixes: 249fa82 ("USB: Add driver to control USB fast charge for iOS devices")
Signed-off-by: Charalampos Mitrodimas <charmitro@posteo.net>
Link: https://lore.kernel.org/r/20250602-apple-mfi-fastcharge-duplicate-sysfs-v1-1-5d84de34fac6@posteo.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: charmitro

drivers/usb/misc/apple-mfi-fastcharge.c

@@ -44,6 +44,7 @@ MODULE_DEVICE_TABLE(usb, mfi_fc_id_table);
 struct mfi_device {
 	struct usb_device *udev;
 	struct power_supply *battery;
+	struct power_supply_desc battery_desc;
 	int charge_type;
 };
 
@@ -178,6 +179,7 @@ static int mfi_fc_probe(struct usb_device *udev)
 {
 	struct power_supply_config battery_cfg = {};
 	struct mfi_device *mfi = NULL;
+	char *battery_name;
 	int err;
 
 	if (!mfi_fc_match(udev))
@@ -187,23 +189,38 @@ static int mfi_fc_probe(struct usb_device *udev)
 	if (!mfi)
 		return -ENOMEM;
 
+	battery_name = kasprintf(GFP_KERNEL, "apple_mfi_fastcharge_%d-%d",
+				 udev->bus->busnum, udev->devnum);
+	if (!battery_name) {
+		err = -ENOMEM;
+		goto err_free_mfi;
+	}
+
+	mfi->battery_desc = apple_mfi_fc_desc;
+	mfi->battery_desc.name = battery_name;
+
 	battery_cfg.drv_data = mfi;
 
 	mfi->charge_type = POWER_SUPPLY_CHARGE_TYPE_TRICKLE;
 	mfi->battery = power_supply_register(&udev->dev,
-						&apple_mfi_fc_desc,
+						&mfi->battery_desc,
 						&battery_cfg);
 	if (IS_ERR(mfi->battery)) {
 		dev_err(&udev->dev, "Can't register battery\n");
 		err = PTR_ERR(mfi->battery);
-		kfree(mfi);
-		return err;
+		goto err_free_name;
 	}
 
 	mfi->udev = usb_get_dev(udev);
 	dev_set_drvdata(&udev->dev, mfi);
 
 	return 0;
+
+err_free_name:
+	kfree(battery_name);
+err_free_mfi:
+	kfree(mfi);
+	return err;
 }
 
 static void mfi_fc_disconnect(struct usb_device *udev)
@@ -213,6 +230,7 @@ static void mfi_fc_disconnect(struct usb_device *udev)
 	mfi = dev_get_drvdata(&udev->dev);
 	if (mfi->battery)
 		power_supply_unregister(mfi->battery);
+	kfree(mfi->battery_desc.name);
 	dev_set_drvdata(&udev->dev, NULL);
 	usb_put_dev(mfi->udev);
 	kfree(mfi);