Bluetooth: btbcm: Try multiple Patch filenames when loading the Patch firmware

Currently the bcm_uart_subver_ and bcm_usb_subver_table-s lack entries
for various newer chipsets. This makes the code use just "BCM" as prefix
for the filename to pass to request-firmware, making it harder for users
to figure out which firmware they need. This especially a problem with
UART attached devices where this leads to the filename being "BCM.hcd".

If we add new entries to the subver-tables now, then this will change
what firmware file the kernel looks for, e.g. currently linux-firmware
contains a brcm/BCM-0bb4-0306.hcd file. If we add the info for the
BCM20703A1 to the subver table, then this will change to
brcm/BCM20703A1-0bb4-0306.hcd. This will cause the file to no longer
get loaded breaking Bluetooth for existing users, going against the
no regressions policy.

To avoid this regression make the btbcm code try multiple filenames,
first try the fullname, e.g. BCM20703A1-0bb4-0306.hcd and if that is
not found, then fallback to the name with just BCM as prefix.

This commit also adds an info message which filename was used,
this makes the output look like this for example:

[   57.387867] Bluetooth: hci0: BCM20703A1
[   57.387870] Bluetooth: hci0: BCM20703A1 (001.001.005) build 0000
[   57.389438] Bluetooth: hci0: BCM20703A1 'brcm/BCM20703A1-0a5c-6410.hcd' Patch
[   58.681769] Bluetooth: hci0: BCM20703A1 Generic USB 20Mhz fcbga_BU
[   58.681772] Bluetooth: hci0: BCM20703A1 (001.001.005) build 0481

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btbcm.c

@@ -28,6 +28,9 @@
 #define BDADDR_BCM43341B (&(bdaddr_t) {{0xac, 0x1f, 0x00, 0x1b, 0x34, 0x43}})
 
 #define BCM_FW_NAME_LEN			64
+#define BCM_FW_NAME_COUNT_MAX		2
+/* For kmalloc-ing the fw-name array instead of putting it on the stack */
+typedef char bcm_fw_name[BCM_FW_NAME_LEN];
 
 int btbcm_check_bdaddr(struct hci_dev *hdev)
 {
@@ -420,11 +423,13 @@ static const struct bcm_subver_table bcm_usb_subver_table[] = {
 int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done)
 {
 	u16 subver, rev, pid, vid;
-	const char *hw_name = "BCM";
 	struct sk_buff *skb;
 	struct hci_rp_read_local_version *ver;
 	const struct bcm_subver_table *bcm_subver_table;
-	char fw_name[BCM_FW_NAME_LEN];
+	const char *hw_name = NULL;
+	char postfix[16] = "";
+	int fw_name_count = 0;
+	bcm_fw_name *fw_name;
 	const struct firmware *fw;
 	int i, err;
 
@@ -464,7 +469,7 @@ int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done)
 	}
 
 	bt_dev_info(hdev, "%s (%3.3u.%3.3u.%3.3u) build %4.4u",
-		    hw_name, (subver & 0xe000) >> 13,
+		    hw_name ? hw_name : "BCM", (subver & 0xe000) >> 13,
 		    (subver & 0x1f00) >> 8, (subver & 0x00ff), rev & 0x0fff);
 
 	if (*fw_load_done)
@@ -480,24 +485,46 @@ int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done)
 		pid = get_unaligned_le16(skb->data + 3);
 		kfree_skb(skb);
 
-		snprintf(fw_name, BCM_FW_NAME_LEN, "brcm/%s-%4.4x-%4.4x.hcd",
+		snprintf(postfix, sizeof(postfix), "-%4.4x-%4.4x", vid, pid);
-			 hw_name, vid, pid);
+	}
+
+	fw_name = kmalloc(BCM_FW_NAME_COUNT_MAX * BCM_FW_NAME_LEN, GFP_KERNEL);
+	if (!fw_name)
+		return -ENOMEM;
+
+	if (hw_name) {
+		snprintf(fw_name[fw_name_count], BCM_FW_NAME_LEN,
+			 "brcm/%s%s.hcd", hw_name, postfix);
+		fw_name_count++;
+	}
+
+	snprintf(fw_name[fw_name_count], BCM_FW_NAME_LEN,
+		 "brcm/BCM%s.hcd", postfix);
+	fw_name_count++;
+
+	for (i = 0; i < fw_name_count; i++) {
+		err = firmware_request_nowarn(&fw, fw_name[i], &hdev->dev);
+		if (err == 0) {
+			bt_dev_info(hdev, "%s '%s' Patch",
+				    hw_name ? hw_name : "BCM", fw_name[i]);
+			*fw_load_done = true;
+			break;
+		}
+	}
+
+	if (*fw_load_done) {
+		err = btbcm_patchram(hdev, fw);
+		if (err)
+			bt_dev_info(hdev, "BCM: Patch failed (%d)", err);
+
+		release_firmware(fw);
 	} else {
-		snprintf(fw_name, BCM_FW_NAME_LEN, "brcm/%s.hcd", hw_name);
+		bt_dev_err(hdev, "BCM: firmware Patch file not found, tried:");
+		for (i = 0; i < fw_name_count; i++)
+			bt_dev_err(hdev, "BCM: '%s'", fw_name[i]);
 	}
 
-	err = request_firmware(&fw, fw_name, &hdev->dev);
+	kfree(fw_name);
-	if (err) {
-		bt_dev_info(hdev, "BCM: Patch %s not found", fw_name);
-		return 0;
-	}
-
-	err = btbcm_patchram(hdev, fw);
-	if (err)
-		bt_dev_info(hdev, "BCM: Patch failed (%d)", err);
-
-	release_firmware(fw);
-	*fw_load_done = true;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(btbcm_initialize);