soc: qcom: Introduce QMI helpers

Drivers that needs to communicate with a remote QMI service all has to
perform the operations of discovering the service, encoding and decoding
the messages and operate the socket. This introduces an abstraction for
these common operations, reducing most of the duplication in such cases.

Acked-by: Chris Lew <clew@codeaurora.org>
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

2 files changed, 849 insertions, 1 deletions

diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
index 37f85b45d0a1..dcebf2814e6d 100644
--- a/drivers/soc/qcom/Makefile
+++ b/drivers/soc/qcom/Makefile
@@ -4,7 +4,7 @@ obj-$(CONFIG_QCOM_GSBI)	+=	qcom_gsbi.o
 obj-$(CONFIG_QCOM_MDT_LOADER)	+= mdt_loader.o
 obj-$(CONFIG_QCOM_PM)	+=	spm.o
 obj-$(CONFIG_QCOM_QMI_HELPERS)	+= qmi_helpers.o
-qmi_helpers-y	+= qmi_encdec.o
+qmi_helpers-y	+= qmi_encdec.o qmi_interface.o
 obj-$(CONFIG_QCOM_RMTFS_MEM)	+= rmtfs_mem.o
 obj-$(CONFIG_QCOM_SMD_RPM)	+= smd-rpm.o
 obj-$(CONFIG_QCOM_SMEM) +=	smem.o
diff --git a/drivers/soc/qcom/qmi_interface.c b/drivers/soc/qcom/qmi_interface.c
new file mode 100644
index 000000000000..877611d5c42b
--- /dev/null
+++ b/drivers/soc/qcom/qmi_interface.c
@@ -0,0 +1,848 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 Linaro Ltd.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/qrtr.h>
+#include <linux/net.h>
+#include <linux/completion.h>
+#include <linux/idr.h>
+#include <linux/string.h>
+#include <net/sock.h>
+#include <linux/workqueue.h>
+#include <linux/soc/qcom/qmi.h>
+
+static struct socket *qmi_sock_create(struct qmi_handle *qmi,
+				      struct sockaddr_qrtr *sq);
+
+/**
+ * qmi_recv_new_server() - handler of NEW_SERVER control message
+ * @qmi:	qmi handle
+ * @service:	service id of the new server
+ * @instance:	instance id of the new server
+ * @node:	node of the new server
+ * @port:	port of the new server
+ *
+ * Calls the new_server callback to inform the client about a newly registered
+ * server matching the currently registered service lookup.
+ */
+static void qmi_recv_new_server(struct qmi_handle *qmi,
+				unsigned int service, unsigned int instance,
+				unsigned int node, unsigned int port)
+{
+	struct qmi_ops *ops = &qmi->ops;
+	struct qmi_service *svc;
+	int ret;
+
+	if (!ops->new_server)
+		return;
+
+	/* Ignore EOF marker */
+	if (!node && !port)
+		return;
+
+	svc = kzalloc(sizeof(*svc), GFP_KERNEL);
+	if (!svc)
+		return;
+
+	svc->service = service;
+	svc->version = instance & 0xff;
+	svc->instance = instance >> 8;
+	svc->node = node;
+	svc->port = port;
+
+	ret = ops->new_server(qmi, svc);
+	if (ret < 0)
+		kfree(svc);
+	else
+		list_add(&svc->list_node, &qmi->lookup_results);
+}
+
+/**
+ * qmi_recv_del_server() - handler of DEL_SERVER control message
+ * @qmi:	qmi handle
+ * @node:	node of the dying server, a value of -1 matches all nodes
+ * @port:	port of the dying server, a value of -1 matches all ports
+ *
+ * Calls the del_server callback for each previously seen server, allowing the
+ * client to react to the disappearing server.
+ */
+static void qmi_recv_del_server(struct qmi_handle *qmi,
+				unsigned int node, unsigned int port)
+{
+	struct qmi_ops *ops = &qmi->ops;
+	struct qmi_service *svc;
+	struct qmi_service *tmp;
+
+	list_for_each_entry_safe(svc, tmp, &qmi->lookup_results, list_node) {
+		if (node != -1 && svc->node != node)
+			continue;
+		if (port != -1 && svc->port != port)
+			continue;
+
+		if (ops->del_server)
+			ops->del_server(qmi, svc);
+
+		list_del(&svc->list_node);
+		kfree(svc);
+	}
+}
+
+/**
+ * qmi_recv_bye() - handler of BYE control message
+ * @qmi:	qmi handle
+ * @node:	id of the dying node
+ *
+ * Signals the client that all previously registered services on this node are
+ * now gone and then calls the bye callback to allow the client client further
+ * cleaning up resources associated with this remote.
+ */
+static void qmi_recv_bye(struct qmi_handle *qmi,
+			 unsigned int node)
+{
+	struct qmi_ops *ops = &qmi->ops;
+
+	qmi_recv_del_server(qmi, node, -1);
+
+	if (ops->bye)
+		ops->bye(qmi, node);
+}
+
+/**
+ * qmi_recv_del_client() - handler of DEL_CLIENT control message
+ * @qmi:	qmi handle
+ * @node:	node of the dying client
+ * @port:	port of the dying client
+ *
+ * Signals the client about a dying client, by calling the del_client callback.
+ */
+static void qmi_recv_del_client(struct qmi_handle *qmi,
+				unsigned int node, unsigned int port)
+{
+	struct qmi_ops *ops = &qmi->ops;
+
+	if (ops->del_client)
+		ops->del_client(qmi, node, port);
+}
+
+static void qmi_recv_ctrl_pkt(struct qmi_handle *qmi,
+			      const void *buf, size_t len)
+{
+	const struct qrtr_ctrl_pkt *pkt = buf;
+
+	if (len < sizeof(struct qrtr_ctrl_pkt)) {
+		pr_debug("ignoring short control packet\n");
+		return;
+	}
+
+	switch (le32_to_cpu(pkt->cmd)) {
+	case QRTR_TYPE_BYE:
+		qmi_recv_bye(qmi, le32_to_cpu(pkt->client.node));
+		break;
+	case QRTR_TYPE_NEW_SERVER:
+		qmi_recv_new_server(qmi,
+				    le32_to_cpu(pkt->server.service),
+				    le32_to_cpu(pkt->server.instance),
+				    le32_to_cpu(pkt->server.node),
+				    le32_to_cpu(pkt->server.port));
+		break;
+	case QRTR_TYPE_DEL_SERVER:
+		qmi_recv_del_server(qmi,
+				    le32_to_cpu(pkt->server.node),
+				    le32_to_cpu(pkt->server.port));
+		break;
+	case QRTR_TYPE_DEL_CLIENT:
+		qmi_recv_del_client(qmi,
+				    le32_to_cpu(pkt->client.node),
+				    le32_to_cpu(pkt->client.port));
+		break;
+	}
+}
+
+static void qmi_send_new_lookup(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qrtr_ctrl_pkt pkt;
+	struct sockaddr_qrtr sq;
+	struct msghdr msg = { };
+	struct kvec iv = { &pkt, sizeof(pkt) };
+	int ret;
+
+	memset(&pkt, 0, sizeof(pkt));
+	pkt.cmd = cpu_to_le32(QRTR_TYPE_NEW_LOOKUP);
+	pkt.server.service = cpu_to_le32(svc->service);
+	pkt.server.instance = cpu_to_le32(svc->version | svc->instance << 8);
+
+	sq.sq_family = qmi->sq.sq_family;
+	sq.sq_node = qmi->sq.sq_node;
+	sq.sq_port = QRTR_PORT_CTRL;
+
+	msg.msg_name = &sq;
+	msg.msg_namelen = sizeof(sq);
+
+	mutex_lock(&qmi->sock_lock);
+	if (qmi->sock) {
+		ret = kernel_sendmsg(qmi->sock, &msg, &iv, 1, sizeof(pkt));
+		if (ret < 0)
+			pr_err("failed to send lookup registration: %d\n", ret);
+	}
+	mutex_unlock(&qmi->sock_lock);
+}
+
+/**
+ * qmi_add_lookup() - register a new lookup with the name service
+ * @qmi:	qmi handle
+ * @service:	service id of the request
+ * @instance:	instance id of the request
+ * @version:	version number of the request
+ *
+ * Registering a lookup query with the name server will cause the name server
+ * to send NEW_SERVER and DEL_SERVER control messages to this socket as
+ * matching services are registered.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int qmi_add_lookup(struct qmi_handle *qmi, unsigned int service,
+		   unsigned int version, unsigned int instance)
+{
+	struct qmi_service *svc;
+
+	svc = kzalloc(sizeof(*svc), GFP_KERNEL);
+	if (!svc)
+		return -ENOMEM;
+
+	svc->service = service;
+	svc->version = version;
+	svc->instance = instance;
+
+	list_add(&svc->list_node, &qmi->lookups);
+
+	qmi_send_new_lookup(qmi, svc);
+
+	return 0;
+}
+EXPORT_SYMBOL(qmi_add_lookup);
+
+static void qmi_send_new_server(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qrtr_ctrl_pkt pkt;
+	struct sockaddr_qrtr sq;
+	struct msghdr msg = { };
+	struct kvec iv = { &pkt, sizeof(pkt) };
+	int ret;
+
+	memset(&pkt, 0, sizeof(pkt));
+	pkt.cmd = cpu_to_le32(QRTR_TYPE_NEW_SERVER);
+	pkt.server.service = cpu_to_le32(svc->service);
+	pkt.server.instance = cpu_to_le32(svc->version | svc->instance << 8);
+	pkt.server.node = cpu_to_le32(qmi->sq.sq_node);
+	pkt.server.port = cpu_to_le32(qmi->sq.sq_port);
+
+	sq.sq_family = qmi->sq.sq_family;
+	sq.sq_node = qmi->sq.sq_node;
+	sq.sq_port = QRTR_PORT_CTRL;
+
+	msg.msg_name = &sq;
+	msg.msg_namelen = sizeof(sq);
+
+	mutex_lock(&qmi->sock_lock);
+	if (qmi->sock) {
+		ret = kernel_sendmsg(qmi->sock, &msg, &iv, 1, sizeof(pkt));
+		if (ret < 0)
+			pr_err("send service registration failed: %d\n", ret);
+	}
+	mutex_unlock(&qmi->sock_lock);
+}
+
+/**
+ * qmi_add_server() - register a service with the name service
+ * @qmi:	qmi handle
+ * @service:	type of the service
+ * @instance:	instance of the service
+ * @version:	version of the service
+ *
+ * Register a new service with the name service. This allows clients to find
+ * and start sending messages to the client associated with @qmi.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int qmi_add_server(struct qmi_handle *qmi, unsigned int service,
+		   unsigned int version, unsigned int instance)
+{
+	struct qmi_service *svc;
+
+	svc = kzalloc(sizeof(*svc), GFP_KERNEL);
+	if (!svc)
+		return -ENOMEM;
+
+	svc->service = service;
+	svc->version = version;
+	svc->instance = instance;
+
+	list_add(&svc->list_node, &qmi->services);
+
+	qmi_send_new_server(qmi, svc);
+
+	return 0;
+}
+EXPORT_SYMBOL(qmi_add_server);
+
+/**
+ * qmi_txn_init() - allocate transaction id within the given QMI handle
+ * @qmi:	QMI handle
+ * @txn:	transaction context
+ * @ei:		description of how to decode a matching response (optional)
+ * @c_struct:	pointer to the object to decode the response into (optional)
+ *
+ * This allocates a transaction id within the QMI handle. If @ei and @c_struct
+ * are specified any responses to this transaction will be decoded as described
+ * by @ei into @c_struct.
+ *
+ * A client calling qmi_txn_init() must call either qmi_txn_wait() or
+ * qmi_txn_cancel() to free up the allocated resources.
+ *
+ * Return: Transaction id on success, negative errno on failure.
+ */
+int qmi_txn_init(struct qmi_handle *qmi, struct qmi_txn *txn,
+		 struct qmi_elem_info *ei, void *c_struct)
+{
+	int ret;
+
+	memset(txn, 0, sizeof(*txn));
+
+	mutex_init(&txn->lock);
+	init_completion(&txn->completion);
+	txn->qmi = qmi;
+	txn->ei = ei;
+	txn->dest = c_struct;
+
+	mutex_lock(&qmi->txn_lock);
+	ret = idr_alloc_cyclic(&qmi->txns, txn, 0, INT_MAX, GFP_KERNEL);
+	if (ret < 0)
+		pr_err("failed to allocate transaction id\n");
+
+	txn->id = ret;
+	mutex_unlock(&qmi->txn_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(qmi_txn_init);
+
+/**
+ * qmi_txn_wait() - wait for a response on a transaction
+ * @txn:	transaction handle
+ * @timeout:	timeout, in jiffies
+ *
+ * If the transaction is decoded by the means of @ei and @c_struct the return
+ * value will be the returned value of qmi_decode_message(), otherwise it's up
+ * to the specified message handler to fill out the result.
+ *
+ * Return: the transaction response on success, negative errno on failure.
+ */
+int qmi_txn_wait(struct qmi_txn *txn, unsigned long timeout)
+{
+	struct qmi_handle *qmi = txn->qmi;
+	int ret;
+
+	ret = wait_for_completion_interruptible_timeout(&txn->completion,
+							timeout);
+
+	mutex_lock(&qmi->txn_lock);
+	mutex_lock(&txn->lock);
+	idr_remove(&qmi->txns, txn->id);
+	mutex_unlock(&txn->lock);
+	mutex_unlock(&qmi->txn_lock);
+
+	if (ret < 0)
+		return ret;
+	else if (ret == 0)
+		return -ETIMEDOUT;
+	else
+		return txn->result;
+}
+EXPORT_SYMBOL(qmi_txn_wait);
+
+/**
+ * qmi_txn_cancel() - cancel an ongoing transaction
+ * @txn:	transaction id
+ */
+void qmi_txn_cancel(struct qmi_txn *txn)
+{
+	struct qmi_handle *qmi = txn->qmi;
+
+	mutex_lock(&qmi->txn_lock);
+	mutex_lock(&txn->lock);
+	idr_remove(&qmi->txns, txn->id);
+	mutex_unlock(&txn->lock);
+	mutex_unlock(&qmi->txn_lock);
+}
+EXPORT_SYMBOL(qmi_txn_cancel);
+
+/**
+ * qmi_invoke_handler() - find and invoke a handler for a message
+ * @qmi:	qmi handle
+ * @sq:		sockaddr of the sender
+ * @txn:	transaction object for the message
+ * @buf:	buffer containing the message
+ * @len:	length of @buf
+ *
+ * Find handler and invoke handler for the incoming message.
+ */
+static void qmi_invoke_handler(struct qmi_handle *qmi, struct sockaddr_qrtr *sq,
+			       struct qmi_txn *txn, const void *buf, size_t len)
+{
+	const struct qmi_msg_handler *handler;
+	const struct qmi_header *hdr = buf;
+	void *dest;
+	int ret;
+
+	if (!qmi->handlers)
+		return;
+
+	for (handler = qmi->handlers; handler->fn; handler++) {
+		if (handler->type == hdr->type &&
+		    handler->msg_id == hdr->msg_id)
+			break;
+	}
+
+	if (!handler->fn)
+		return;
+
+	dest = kzalloc(handler->decoded_size, GFP_KERNEL);
+	if (!dest)
+		return;
+
+	ret = qmi_decode_message(buf, len, handler->ei, dest);
+	if (ret < 0)
+		pr_err("failed to decode incoming message\n");
+	else
+		handler->fn(qmi, sq, txn, dest);
+
+	kfree(dest);
+}
+
+/**
+ * qmi_handle_net_reset() - invoked to handle ENETRESET on a QMI handle
+ * @qmi:	the QMI context
+ *
+ * As a result of registering a name service with the QRTR all open sockets are
+ * flagged with ENETRESET and this function will be called. The typical case is
+ * the initial boot, where this signals that the local node id has been
+ * configured and as such any bound sockets needs to be rebound. So close the
+ * socket, inform the client and re-initialize the socket.
+ *
+ * For clients it's generally sufficient to react to the del_server callbacks,
+ * but server code is expected to treat the net_reset callback as a "bye" from
+ * all nodes.
+ *
+ * Finally the QMI handle will send out registration requests for any lookups
+ * and services.
+ */
+static void qmi_handle_net_reset(struct qmi_handle *qmi)
+{
+	struct sockaddr_qrtr sq;
+	struct qmi_service *svc;
+	struct socket *sock;
+
+	sock = qmi_sock_create(qmi, &sq);
+	if (IS_ERR(sock))
+		return;
+
+	mutex_lock(&qmi->sock_lock);
+	sock_release(qmi->sock);
+	qmi->sock = NULL;
+	mutex_unlock(&qmi->sock_lock);
+
+	qmi_recv_del_server(qmi, -1, -1);
+
+	if (qmi->ops.net_reset)
+		qmi->ops.net_reset(qmi);
+
+	mutex_lock(&qmi->sock_lock);
+	qmi->sock = sock;
+	qmi->sq = sq;
+	mutex_unlock(&qmi->sock_lock);
+
+	list_for_each_entry(svc, &qmi->lookups, list_node)
+		qmi_send_new_lookup(qmi, svc);
+
+	list_for_each_entry(svc, &qmi->services, list_node)
+		qmi_send_new_server(qmi, svc);
+}
+
+static void qmi_handle_message(struct qmi_handle *qmi,
+			       struct sockaddr_qrtr *sq,
+			       const void *buf, size_t len)
+{
+	const struct qmi_header *hdr;
+	struct qmi_txn tmp_txn;
+	struct qmi_txn *txn = NULL;
+	int ret;
+
+	if (len < sizeof(*hdr)) {
+		pr_err("ignoring short QMI packet\n");
+		return;
+	}
+
+	hdr = buf;
+
+	/* If this is a response, find the matching transaction handle */
+	if (hdr->type == QMI_RESPONSE) {
+		mutex_lock(&qmi->txn_lock);
+		txn = idr_find(&qmi->txns, hdr->txn_id);
+
+		/* Ignore unexpected responses */
+		if (!txn) {
+			mutex_unlock(&qmi->txn_lock);
+			return;
+		}
+
+		mutex_lock(&txn->lock);
+		mutex_unlock(&qmi->txn_lock);
+
+		if (txn->dest && txn->ei) {
+			ret = qmi_decode_message(buf, len, txn->ei, txn->dest);
+			if (ret < 0)
+				pr_err("failed to decode incoming message\n");
+
+			txn->result = ret;
+			complete(&txn->completion);
+		} else  {
+			qmi_invoke_handler(qmi, sq, txn, buf, len);
+		}
+
+		mutex_unlock(&txn->lock);
+	} else {
+		/* Create a txn based on the txn_id of the incoming message */
+		memset(&tmp_txn, 0, sizeof(tmp_txn));
+		tmp_txn.id = hdr->txn_id;
+
+		qmi_invoke_handler(qmi, sq, &tmp_txn, buf, len);
+	}
+}
+
+static void qmi_data_ready_work(struct work_struct *work)
+{
+	struct qmi_handle *qmi = container_of(work, struct qmi_handle, work);
+	struct qmi_ops *ops = &qmi->ops;
+	struct sockaddr_qrtr sq;
+	struct msghdr msg = { .msg_name = &sq, .msg_namelen = sizeof(sq) };
+	struct kvec iv;
+	ssize_t msglen;
+
+	for (;;) {
+		iv.iov_base = qmi->recv_buf;
+		iv.iov_len = qmi->recv_buf_size;
+
+		mutex_lock(&qmi->sock_lock);
+		if (qmi->sock)
+			msglen = kernel_recvmsg(qmi->sock, &msg, &iv, 1,
+						iv.iov_len, MSG_DONTWAIT);
+		else
+			msglen = -EPIPE;
+		mutex_unlock(&qmi->sock_lock);
+		if (msglen == -EAGAIN)
+			break;
+
+		if (msglen == -ENETRESET) {
+			qmi_handle_net_reset(qmi);
+
+			/* The old qmi->sock is gone, our work is done */
+			break;
+		}
+
+		if (msglen < 0) {
+			pr_err("qmi recvmsg failed: %zd\n", msglen);
+			break;
+		}
+
+		if (sq.sq_node == qmi->sq.sq_node &&
+		    sq.sq_port == QRTR_PORT_CTRL) {
+			qmi_recv_ctrl_pkt(qmi, qmi->recv_buf, msglen);
+		} else if (ops->msg_handler) {
+			ops->msg_handler(qmi, &sq, qmi->recv_buf, msglen);
+		} else {
+			qmi_handle_message(qmi, &sq, qmi->recv_buf, msglen);
+		}
+	}
+}
+
+static void qmi_data_ready(struct sock *sk)
+{
+	struct qmi_handle *qmi = sk->sk_user_data;
+
+	/*
+	 * This will be NULL if we receive data while being in
+	 * qmi_handle_release()
+	 */
+	if (!qmi)
+		return;
+
+	queue_work(qmi->wq, &qmi->work);
+}
+
+static struct socket *qmi_sock_create(struct qmi_handle *qmi,
+				      struct sockaddr_qrtr *sq)
+{
+	struct socket *sock;
+	int sl = sizeof(*sq);
+	int ret;
+
+	ret = sock_create_kern(&init_net, AF_QIPCRTR, SOCK_DGRAM,
+			       PF_QIPCRTR, &sock);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	ret = kernel_getsockname(sock, (struct sockaddr *)sq, &sl);
+	if (ret < 0) {
+		sock_release(sock);
+		return ERR_PTR(ret);
+	}
+
+	sock->sk->sk_user_data = qmi;
+	sock->sk->sk_data_ready = qmi_data_ready;
+	sock->sk->sk_error_report = qmi_data_ready;
+
+	return sock;
+}
+
+/**
+ * qmi_handle_init() - initialize a QMI client handle
+ * @qmi:	QMI handle to initialize
+ * @recv_buf_size: maximum size of incoming message
+ * @ops:	reference to callbacks for QRTR notifications
+ * @handlers:	NULL-terminated list of QMI message handlers
+ *
+ * This initializes the QMI client handle to allow sending and receiving QMI
+ * messages. As messages are received the appropriate handler will be invoked.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int qmi_handle_init(struct qmi_handle *qmi, size_t recv_buf_size,
+		    const struct qmi_ops *ops,
+		    const struct qmi_msg_handler *handlers)
+{
+	int ret;
+
+	mutex_init(&qmi->txn_lock);
+	mutex_init(&qmi->sock_lock);
+
+	idr_init(&qmi->txns);
+
+	INIT_LIST_HEAD(&qmi->lookups);
+	INIT_LIST_HEAD(&qmi->lookup_results);
+	INIT_LIST_HEAD(&qmi->services);
+
+	INIT_WORK(&qmi->work, qmi_data_ready_work);
+
+	qmi->handlers = handlers;
+	if (ops)
+		qmi->ops = *ops;
+
+	if (recv_buf_size < sizeof(struct qrtr_ctrl_pkt))
+		recv_buf_size = sizeof(struct qrtr_ctrl_pkt);
+	else
+		recv_buf_size += sizeof(struct qmi_header);
+
+	qmi->recv_buf_size = recv_buf_size;
+	qmi->recv_buf = kzalloc(recv_buf_size, GFP_KERNEL);
+	if (!qmi->recv_buf)
+		return -ENOMEM;
+
+	qmi->wq = alloc_workqueue("qmi_msg_handler", WQ_UNBOUND, 1);
+	if (!qmi->wq) {
+		ret = -ENOMEM;
+		goto err_free_recv_buf;
+	}
+
+	qmi->sock = qmi_sock_create(qmi, &qmi->sq);
+	if (IS_ERR(qmi->sock)) {
+		pr_err("failed to create QMI socket\n");
+		ret = PTR_ERR(qmi->sock);
+		goto err_destroy_wq;
+	}
+
+	return 0;
+
+err_destroy_wq:
+	destroy_workqueue(qmi->wq);
+err_free_recv_buf:
+	kfree(qmi->recv_buf);
+
+	return ret;
+}
+EXPORT_SYMBOL(qmi_handle_init);
+
+/**
+ * qmi_handle_release() - release the QMI client handle
+ * @qmi:	QMI client handle
+ *
+ * This closes the underlying socket and stops any handling of QMI messages.
+ */
+void qmi_handle_release(struct qmi_handle *qmi)
+{
+	struct socket *sock = qmi->sock;
+	struct qmi_service *svc, *tmp;
+
+	sock->sk->sk_user_data = NULL;
+	cancel_work_sync(&qmi->work);
+
+	qmi_recv_del_server(qmi, -1, -1);
+
+	mutex_lock(&qmi->sock_lock);
+	sock_release(sock);
+	qmi->sock = NULL;
+	mutex_unlock(&qmi->sock_lock);
+
+	destroy_workqueue(qmi->wq);
+
+	idr_destroy(&qmi->txns);
+
+	kfree(qmi->recv_buf);
+
+	/* Free registered lookup requests */
+	list_for_each_entry_safe(svc, tmp, &qmi->lookups, list_node) {
+		list_del(&svc->list_node);
+		kfree(svc);
+	}
+
+	/* Free registered service information */
+	list_for_each_entry_safe(svc, tmp, &qmi->services, list_node) {
+		list_del(&svc->list_node);
+		kfree(svc);
+	}
+}
+EXPORT_SYMBOL(qmi_handle_release);
+
+/**
+ * qmi_send_message() - send a QMI message
+ * @qmi:	QMI client handle
+ * @sq:		destination sockaddr
+ * @txn:	transaction object to use for the message
+ * @type:	type of message to send
+ * @msg_id:	message id
+ * @len:	max length of the QMI message
+ * @ei:		QMI message description
+ * @c_struct:	object to be encoded
+ *
+ * This function encodes @c_struct using @ei into a message of type @type,
+ * with @msg_id and @txn into a buffer of maximum size @len, and sends this to
+ * @sq.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+static ssize_t qmi_send_message(struct qmi_handle *qmi,
+				struct sockaddr_qrtr *sq, struct qmi_txn *txn,
+				int type, int msg_id, size_t len,
+				struct qmi_elem_info *ei, const void *c_struct)
+{
+	struct msghdr msghdr = {};
+	struct kvec iv;
+	void *msg;
+	int ret;
+
+	msg = qmi_encode_message(type,
+				 msg_id, &len,
+				 txn->id, ei,
+				 c_struct);
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
+
+	iv.iov_base = msg;
+	iv.iov_len = len;
+
+	if (sq) {
+		msghdr.msg_name = sq;
+		msghdr.msg_namelen = sizeof(*sq);
+	}
+
+	mutex_lock(&qmi->sock_lock);
+	if (qmi->sock) {
+		ret = kernel_sendmsg(qmi->sock, &msghdr, &iv, 1, len);
+		if (ret < 0)
+			pr_err("failed to send QMI message\n");
+	} else {
+		ret = -EPIPE;
+	}
+	mutex_unlock(&qmi->sock_lock);
+
+	kfree(msg);
+
+	return ret < 0 ? ret : 0;
+}
+
+/**
+ * qmi_send_request() - send a request QMI message
+ * @qmi:	QMI client handle
+ * @sq:		destination sockaddr
+ * @txn:	transaction object to use for the message
+ * @msg_id:	message id
+ * @len:	max length of the QMI message
+ * @ei:		QMI message description
+ * @c_struct:	object to be encoded
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+ssize_t qmi_send_request(struct qmi_handle *qmi, struct sockaddr_qrtr *sq,
+			 struct qmi_txn *txn, int msg_id, size_t len,
+			 struct qmi_elem_info *ei, const void *c_struct)
+{
+	return qmi_send_message(qmi, sq, txn, QMI_REQUEST, msg_id, len, ei,
+				c_struct);
+}
+EXPORT_SYMBOL(qmi_send_request);
+
+/**
+ * qmi_send_response() - send a response QMI message
+ * @qmi:	QMI client handle
+ * @sq:		destination sockaddr
+ * @txn:	transaction object to use for the message
+ * @msg_id:	message id
+ * @len:	max length of the QMI message
+ * @ei:		QMI message description
+ * @c_struct:	object to be encoded
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+ssize_t qmi_send_response(struct qmi_handle *qmi, struct sockaddr_qrtr *sq,
+			  struct qmi_txn *txn, int msg_id, size_t len,
+			  struct qmi_elem_info *ei, const void *c_struct)
+{
+	return qmi_send_message(qmi, sq, txn, QMI_RESPONSE, msg_id, len, ei,
+				c_struct);
+}
+EXPORT_SYMBOL(qmi_send_response);
+
+/**
+ * qmi_send_indication() - send an indication QMI message
+ * @qmi:	QMI client handle
+ * @sq:		destination sockaddr
+ * @msg_id:	message id
+ * @len:	max length of the QMI message
+ * @ei:		QMI message description
+ * @c_struct:	object to be encoded
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+ssize_t qmi_send_indication(struct qmi_handle *qmi, struct sockaddr_qrtr *sq,
+			    int msg_id, size_t len, struct qmi_elem_info *ei,
+			    const void *c_struct)
+{
+	struct qmi_txn txn;
+	ssize_t rval;
+	int ret;
+
+	ret = qmi_txn_init(qmi, &txn, NULL, NULL);
+	if (ret < 0)
+		return ret;
+
+	rval = qmi_send_message(qmi, sq, &txn, QMI_INDICATION, msg_id, len, ei,
+				c_struct);
+
+	/* We don't care about future messages on this txn */
+	qmi_txn_cancel(&txn);
+
+	return rval;
+}
+EXPORT_SYMBOL(qmi_send_indication);