[PATCH 2/3] Bluetooth: btmtk: Improve BT firmware logging

The firmware log line in btmtk_setup_firmware_79xx() never says which
file was requested, which matters because btmtk_fw_get_filename() derives
the name from the device id and firmware version at runtime. It reports
the firmware's own hwver field as the HW version, when the device id the
driver read from the chip is the more useful value and is already
available as dev_id. And it prints datetime, a u8[16] with no guaranteed
NUL terminator, with %s.

Log the filename before the image is parsed, so a file that fails
validation still says which file it was, report dev_id as the HW version,
and bound datetime with %.16s.

The datetime change is hardening rather than a fix, hence no Fixes: tag:
every file in linux-firmware terminates the field, and provoking the
over-read needs a malformed file in /lib/firmware.

Log output on MT7922 after the change:

  [  365.245951] Bluetooth: hci0: Loading BT firmware: mediatek/BT_RAM_CODE_MT7922_1_1_hdr.bin
  [  365.245956] Bluetooth: hci0: BT HW ver: 0x7922, SW ver: 0x008a, Build Time: 20260605203811

Signed-off-by: Chris Lu <redacted>
Assisted-by: Claude:claude-opus-5
---
 drivers/bluetooth/btmtk.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index 07a7a7a3656a..cf4f40349afa 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c

@@ -214,6 +214,8 @@ int btmtk_setup_firmware_79xx(struct hci_dev *hdev, const char *fwname,
 		return err;
 	}
 
+	bt_dev_info(hdev, "Loading BT firmware: %s", fwname);
+
 	err = btmtk_fw_validate_layout(hdev, fw, &section_num);
 	if (err < 0)
 		goto err_release_fw;

@@ -222,8 +224,8 @@ int btmtk_setup_firmware_79xx(struct hci_dev *hdev, const char *fwname,
 	fw_bin_ptr = fw_ptr;
 	hdr = (struct btmtk_patch_header *)fw_ptr;
 
-	bt_dev_info(hdev, "HW/SW Version: 0x%04x%04x, Build Time: %s",
-		    le16_to_cpu(hdr->hwver), le16_to_cpu(hdr->swver), hdr->datetime);
+	bt_dev_info(hdev, "BT HW ver: 0x%04x, SW ver: 0x%04x, Build Time: %.16s",
+		    dev_id & 0xffff, le16_to_cpu(hdr->swver), hdr->datetime);
 
 	for (i = 0; i < section_num; i++) {
 		first_block = 1;

-- 
2.45.2