Texas Instrument's Bluetooth Driver For Shared Transport 笔记

这篇笔记探讨了Texas Instruments的Bluetooth Driver如何作为HCI核心与TI Shared Transport Layer之间的接口。主要内容包括`Btwilink.c`中的`st_proto_s`结构体定义，详细解析了该结构体的各项成员，如接收函数、匹配包函数、注册完成回调等，旨在理解蓝牙驱动在Android系统中的工作原理。

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Bluetooth Driver acts as interface between HCI core and TI Shared Transport Layer.

/drivers/bluetooth/Btwilink.c:

 
#include <linux/platform_device.h>
#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
#include <net/bluetooth/hci.h>
#include <linux/ti_wilink_st.h>
#include <linux/module.h>
#define DEBUG
#define VERSION               "1.0"
#define MAX_BT_CHNL_IDS		3
#define BT_REGISTER_TIMEOUT   6000

struct ti_st {
	struct hci_dev *hdev;
	char reg_status;
	long (*st_write) (struct sk_buff *);
	struct completion wait_reg_completion;
};

struct ti_st - 模块操作结构体
@hdev: HCI 设备指针绑定到了蓝牙模块
@reg_status: ST 注册返回状态
@st_write: send_frame 用到的写函数
@wait_reg_completion - ti_st_open and st_reg_completion_cb之间的结束同步

static inline void ti_st_tx_complete(struct ti_st *hst, int pkt_type)
{
	struct hci_dev *hdev = hst->hdev;

	/* Update HCI stat counters */
	switch (pkt_type) {
	case HCI_COMMAND_PKT:
		hdev->stat.cmd_tx++;
		break;

	case HCI_ACLDATA_PKT:
		hdev->stat.acl_tx++;
		break;

	case HCI_SCODATA_PKT:
		hdev->stat.sco_tx++;
		break;
	}
}

pocket ID (cmd,acl,sco)计数

static void st_reg_completion_cb(void *priv_data, char data)
{
	struct ti_st *lhst = priv_data;

	/* Save registration status for use in ti_st_open() */
	lhst->reg_status = data;
	/* complete the wait in ti_st_open() */
	complete(&lhst->wait_reg_completion);
}

status.ti_st_open() 函数会等待st_register() 返回的ST_PENDING信号

static long st_receive(void *priv_data, struct sk_buff *skb)
{
	struct ti_st *lhst = priv_data;
	int err;

	if (!skb)
		return -EFAULT;

	if (!lhst) {
		kfree_skb(skb);
		return -EFAULT;
	}
	skb->dev = (void *) lhst->hdev;

	/* Forward skb to HCI core layer */
	err = hci_recv_frame(skb);
	if (err < 0) {
		BT_ERR("Unable to push skb to HCI core(%d)", err);
		return err;
	}
	lhst->hdev->stat.byte_rx += skb->len;
	return 0;
}

接收到数据时被Shared Transport层调用

static struct st_proto_s ti_st_proto[MAX_BT_CHNL_IDS] = {
	{
		.chnl_id = HCI_EVENT_PKT, /* HCI Events */
		.hdr_len = sizeof(struct hci_event_hdr),
		.offset_len_in_hdr = offsetof(struct hci_event_hdr, plen),
		.len_size = 1, /* sizeof(plen) in struct hci_event_hdr */
		.reserve = 8,
	},
	{
		.chnl_id = HCI_ACLDATA_PKT, /* ACL */
		.hdr_len = sizeof(struct hci_acl_hdr),
		.offset_len_in_hdr = offsetof(struct hci_acl_hdr, dlen),
		.len_size = 2,	/* sizeof(dlen) in struct hci_acl_hdr */
		.reserve = 8,
	},
	{
		.chnl_id = HCI_SCODATA_PKT, /* SCO */
		.hdr_len = sizeof(struct hci_sco_hdr),
		.offset_len_in_hdr = offsetof(struct hci_sco_hdr, dlen),
		.len_size = 1, /* sizeof(dlen) in struct hci_sco_hdr */
		.reserve = 8,
	},
};

HCI 层的接口

struct st_proto_s的定义：/include/linux/ti_wilink_st.h:

struct st_proto_s {
   enum proto_type type;
   long (*recv) (void *, struct sk_buff *);
   unsigned char (*match_packet) (const unsigned char *data);
   void (*reg_complete_cb) (void *, char data);
   long (*write) (struct sk_buff *skb);
   void *priv_data;
   unsigned char chnl_id;
   unsigned short max_frame_size; //能接收的最大帧的大小
   unsigned char hdr_len;    //头结构的长度
   unsigned char offset_len_in_hdr;    //提供头结构中的长度偏移
   unsigned char len_size;   //2字节或1字节
   unsigned char reserve;   //ST 需要交换的字节数 };

static int ti_st_open(struct hci_dev *hdev)
{
	unsigned long timeleft;
	struct ti_st *hst;
	int err, i;

	BT_DBG("%s %p", hdev->name, hdev);

	if (test_and_set_bit(HCI_RUNNING, &hdev->flags))
		return -EBUSY;

	/* provide contexts for callbacks from ST */
	hst = hdev->driver_data;

	for (i = 0; i < MAX_BT_CHNL_IDS; i++) {
		ti_st_proto[i].priv_data = hst;
		ti_st_proto[i].max_frame_size = HCI_MAX_FRAME_SIZE;
		ti_st_proto[i].recv = st_receive;
		ti_st_proto[i].reg_complete_cb = st_reg_completion_cb;

		/* Prepare wait-for-completion handler */
		init_completion(&hst->wait_reg_completion);
		/* Reset ST registration callback status flag,
		 * this value will be updated in
		 * st_reg_completion_cb()
		 * function whenever it called from ST driver.
		 */
		hst->reg_status = -EINPROGRESS;

		err = st_register(&ti_st_proto[i]);
		if (!err)
			goto done;

		if (err != -EINPROGRESS) {
			clear_bit(HCI_RUNNING, &hdev->flags);
			BT_ERR("st_register failed %d", err);
			return err;
		}

		/* ST is busy with either protocol
		 * registration or firmware download.
		 */
		BT_DBG("waiting for registration "
				"completion signal from ST");
		timeleft = wait_for_completion_timeout
			(&hst->wait_reg_completion,
			 msecs_to_jiffies(BT_REGISTER_TIMEOUT));
		if (!timeleft) {
			clear_bit(HCI_RUNNING, &hdev->flags);
			BT_ERR("Timeout(%d sec),didn't get reg "
					"completion signal from ST",
					BT_REGISTER_TIMEOUT / 1000);
			return -ETIMEDOUT;
		}

		/* Is ST registration callback
		 * called with ERROR status? */
		if (hst->reg_status != 0) {
			clear_bit(HCI_RUNNING, &hdev->flags);
			BT_ERR("ST registration completed with invalid "
					"status %d", hst->reg_status);
			return -EAGAIN;
		}

done:
		hst->st_write = ti_st_proto[i].write;
		if (!hst->st_write) {
			BT_ERR("undefined ST write function");
			clear_bit(HCI_RUNNING, &hdev->flags);
			for (i = 0; i < MAX_BT_CHNL_IDS; i++) {
				/* Undo registration with ST */
				err = st_unregister(&ti_st_proto[i]);
				if (err)
					BT_ERR("st_unregister() failed with "
							"error %d", err);
				hst->st_write = NULL;
			}
			return -EIO;
		}
	}
	return 0;
}

HCI core调用，初始化设备

static int ti_st_close(struct hci_dev *hdev)
{
	int err, i;
	struct ti_st *hst = hdev->driver_data;

	if (!test_and_clear_bit(HCI_RUNNING, &hdev->flags))
		return 0;

	for (i = MAX_BT_CHNL_IDS-1; i >= 0; i--) {
		err = st_unregister(&ti_st_proto[i]);
		if (err)
			BT_ERR("st_unregister(%d) failed with error %d",
					ti_st_proto[i].chnl_id, err);
	}

	hst->st_write = NULL;

	return err;
}

关闭设备

static int ti_st_send_frame(struct sk_buff *skb)
{
	struct hci_dev *hdev;
	struct ti_st *hst;
	long len;

	hdev = (struct hci_dev *)skb->dev;

	if (!test_bit(HCI_RUNNING, &hdev->flags))
		return -EBUSY;

	hst = hdev->driver_data;

	/* Prepend skb with frame type */
	memcpy(skb_push(skb, 1), &bt_cb(skb)->pkt_type, 1);

	BT_DBG("%s: type %d len %d", hdev->name, bt_cb(skb)->pkt_type,
			skb->len);

	/* Insert skb to shared transport layer's transmit queue.
	 * Freeing skb memory is taken care in shared transport layer,
	 * so don't free skb memory here.
	 */
	len = hst->st_write(skb);
	if (len < 0) {
		kfree_skb(skb);
		BT_ERR("ST write failed (%ld)", len);
		/* Try Again, would only fail if UART has gone bad */
		return -EAGAIN;
	}

	/* ST accepted our skb. So, Go ahead and do rest */
	hdev->stat.byte_tx += len;
	ti_st_tx_complete(hst, bt_cb(skb)->pkt_type);

	return 0;
}

static void ti_st_destruct(struct hci_dev *hdev)
{
	BT_DBG("%s", hdev->name);
	/* do nothing here, since platform remove
	 * would free the hdev->driver_data
	 */
}

发送帧

static int bt_ti_probe(struct platform_device *pdev)
{
	static struct ti_st *hst;
	struct hci_dev *hdev;
	int err;

	hst = kzalloc(sizeof(struct ti_st), GFP_KERNEL);
	if (!hst)
		return -ENOMEM;

	/* Expose "hciX" device to user space */
	hdev = hci_alloc_dev();
	if (!hdev) {
		kfree(hst);
		return -ENOMEM;
	}

	BT_DBG("hdev %p", hdev);

	hst->hdev = hdev;
	hdev->bus = HCI_UART;
	hdev->driver_data = hst;
	hdev->open = ti_st_open;
	hdev->close = ti_st_close;
	hdev->flush = NULL;
	hdev->send = ti_st_send_frame;
	hdev->destruct = ti_st_destruct;
	hdev->owner = THIS_MODULE;

	err = hci_register_dev(hdev);
	if (err < 0) {
		BT_ERR("Can't register HCI device error %d", err);
		kfree(hst);
		hci_free_dev(hdev);
		return err;
	}

	BT_DBG("HCI device registered (hdev %p)", hdev);

	dev_set_drvdata(&pdev->dev, hst);
	return err;
}

设备探测

static int bt_ti_remove(struct platform_device *pdev)
{
	struct hci_dev *hdev;
	struct ti_st *hst = dev_get_drvdata(&pdev->dev);

	if (!hst)
		return -EFAULT;

	BT_DBG("%s", hst->hdev->name);

	hdev = hst->hdev;
	ti_st_close(hdev);
	hci_unregister_dev(hdev);

	hci_free_dev(hdev);
	kfree(hst);

	dev_set_drvdata(&pdev->dev, NULL);
	return 0;
}

设备卸载

static struct platform_driver btwilink_driver = {
	.probe = bt_ti_probe,
	.remove = bt_ti_remove,
	.driver = {
		.name = "btwilink",
		.owner = THIS_MODULE,
	},
};

platform driver

static int __init btwilink_init(void)
{
	BT_INFO("Bluetooth Driver for TI WiLink - Version %s", VERSION);

	return platform_driver_register(&btwilink_driver);
}

static void __exit btwilink_exit(void)
{
	platform_driver_unregister(&btwilink_driver);
}

module_init(btwilink_init);
module_exit(btwilink_exit);

设备 init 与 exit

MODULE_AUTHOR("Raja Mani <raja_mani@ti.com>");
MODULE_DESCRIPTION("Bluetooth Driver for TI Shared Transport" VERSION);
MODULE_VERSION(VERSION);
MODULE_LICENSE("GPL");