Bluetooth: btusb: Add HCI Drv commands for configuring altsetting

JIRA: https://issues.redhat.com/browse/RHEL-93657

commit 7d70989
Author: Hsin-chen Chuang <chharry@chromium.org>
Date:   Wed Apr 16 09:53:36 2025 +0000

    Bluetooth: btusb: Add HCI Drv commands for configuring altsetting

    Although commit 75ddcd5 ("Bluetooth: btusb: Configure altsetting
    for HCI_USER_CHANNEL") has enabled the HCI_USER_CHANNEL user to send out
    SCO data through USB Bluetooth chips, it's observed that with the patch
    HFP is flaky on most of the existing USB Bluetooth controllers: Intel
    chips sometimes send out no packet for Transparent codec; MTK chips may
    generate SCO data with a wrong handle for CVSD codec; RTK could split
    the data with a wrong packet size for Transparent codec; ... etc.

    To address the issue above one needs to reset the altsetting back to
    zero when there is no active SCO connection, which is the same as the
    BlueZ behavior, and another benefit is the bus doesn't need to reserve
    bandwidth when no SCO connection.

    This patch adds "Supported Altsettings" and "Switch Altsetting" commands
    that allow the user space program to configure the altsetting freely.

    This patch is tested on ChromeOS devices. The USB Bluetooth models
    (CVSD, TRANS alt3, and TRANS alt6) could pass the stress HFP test narrow
    band speech and wide band speech.

    Cc: chromeos-bluetooth-upstreaming@chromium.org
    Fixes: b16b327 ("Bluetooth: btusb: add sysfs attribute to control USB alt setting")
    Signed-off-by: Hsin-chen Chuang <chharry@chromium.org>
    Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Signed-off-by: David Marlin <dmarlin@redhat.com>

Author: damarlin

drivers/bluetooth/btusb.c

@@ -3743,12 +3743,31 @@ static ssize_t isoc_alt_store(struct device *dev,
 
 static DEVICE_ATTR_RW(isoc_alt);
 
+#define BTUSB_HCI_DRV_OP_SUPPORTED_ALTSETTINGS \
+		hci_opcode_pack(HCI_DRV_OGF_DRIVER_SPECIFIC, 0x0000)
+#define BTUSB_HCI_DRV_SUPPORTED_ALTSETTINGS_SIZE	0
+struct btusb_hci_drv_rp_supported_altsettings {
+	__u8	num;
+	__u8	altsettings[];
+} __packed;
+
+#define BTUSB_HCI_DRV_OP_SWITCH_ALTSETTING \
+		hci_opcode_pack(HCI_DRV_OGF_DRIVER_SPECIFIC, 0x0001)
+#define BTUSB_HCI_DRV_SWITCH_ALTSETTING_SIZE		1
+struct btusb_hci_drv_cmd_switch_altsetting {
+	__u8	altsetting;
+} __packed;
+
 static const struct {
 	u16 opcode;
 	const char *desc;
 } btusb_hci_drv_supported_commands[] = {
 	/* Common commands */
 	{ HCI_DRV_OP_READ_INFO, "Read Info" },
+
+	/* Driver specific commands */
+	{ BTUSB_HCI_DRV_OP_SUPPORTED_ALTSETTINGS, "Supported Altsettings" },
+	{ BTUSB_HCI_DRV_OP_SWITCH_ALTSETTING,     "Switch Altsetting" },
 };
 static int btusb_hci_drv_read_info(struct hci_dev *hdev, void *data,
 				   u16 data_len)
@@ -3785,11 +3804,65 @@ static int btusb_hci_drv_read_info(struct hci_dev *hdev, void *data,
 	return err;
 }
 
+static int btusb_hci_drv_supported_altsettings(struct hci_dev *hdev, void *data,
+					       u16 data_len)
+{
+	struct btusb_data *drvdata = hci_get_drvdata(hdev);
+	struct btusb_hci_drv_rp_supported_altsettings *rp;
+	size_t rp_size;
+	int err;
+	u8 i;
+
+	/* There are at most 7 alt (0 - 6) */
+	rp = kmalloc(sizeof(*rp) + 7, GFP_KERNEL);
+
+	rp->num = 0;
+	if (!drvdata->isoc)
+		goto done;
+
+	for (i = 0; i <= 6; i++) {
+		if (btusb_find_altsetting(drvdata, i))
+			rp->altsettings[rp->num++] = i;
+	}
+
+done:
+	rp_size = sizeof(*rp) + rp->num;
+
+	err = hci_drv_cmd_complete(hdev, BTUSB_HCI_DRV_OP_SUPPORTED_ALTSETTINGS,
+				   HCI_DRV_STATUS_SUCCESS, rp, rp_size);
+	kfree(rp);
+	return err;
+}
+
+static int btusb_hci_drv_switch_altsetting(struct hci_dev *hdev, void *data,
+					   u16 data_len)
+{
+	struct btusb_hci_drv_cmd_switch_altsetting *cmd = data;
+	u8 status;
+
+	if (cmd->altsetting > 6) {
+		status = HCI_DRV_STATUS_INVALID_PARAMETERS;
+	} else {
+		if (btusb_switch_alt_setting(hdev, cmd->altsetting))
+			status = HCI_DRV_STATUS_UNSPECIFIED_ERROR;
+		else
+			status = HCI_DRV_STATUS_SUCCESS;
+	}
+
+	return hci_drv_cmd_status(hdev, BTUSB_HCI_DRV_OP_SWITCH_ALTSETTING,
+				  status);
+}
+
 static const struct hci_drv_handler btusb_hci_drv_common_handlers[] = {
 	{ btusb_hci_drv_read_info,	HCI_DRV_READ_INFO_SIZE },
 };
 
-static const struct hci_drv_handler btusb_hci_drv_specific_handlers[] = {};
+static const struct hci_drv_handler btusb_hci_drv_specific_handlers[] = {
+	{ btusb_hci_drv_supported_altsettings,
+				BTUSB_HCI_DRV_SUPPORTED_ALTSETTINGS_SIZE },
+	{ btusb_hci_drv_switch_altsetting,
+				BTUSB_HCI_DRV_SWITCH_ALTSETTING_SIZE },
+};
 
 static struct hci_drv btusb_hci_drv = {
 	.common_handler_count	= ARRAY_SIZE(btusb_hci_drv_common_handlers),