[PATCHv3 2/6] mailbox: Introduce a new common API

Jassi Brar
2014-02-15T18:25:46Z

Introduce common framework for client/protocol drivers and
controller drivers of Inter-Processor-Communication (IPC).

Client driver developers should have a look at
include/linux/mailbox_client.h to understand the part of
the API exposed to client drivers.
Similarly controller driver developers should have a look
at include/linux/mailbox_controller.h

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
---
drivers/mailbox/Makefile | 4 +
drivers/mailbox/mailbox.c | 534 +++++++++++++++++++++++++++++++++++++
include/linux/mailbox.h | 17 ++
include/linux/mailbox_client.h | 87 ++++++
include/linux/mailbox_controller.h | 102 +++++++
5 files changed, 744 insertions(+)
create mode 100644 drivers/mailbox/mailbox.c
create mode 100644 include/linux/mailbox.h
create mode 100644 include/linux/mailbox_client.h
create mode 100644 include/linux/mailbox_controller.h

diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index e0facb3..2fa343a 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -1,3 +1,7 @@
+# Generic MAILBOX API
+
+obj-$(CONFIG_MAILBOX) += mailbox.o
+
obj-$(CONFIG_PL320_MBOX) += pl320-ipc.o

obj-$(CONFIG_OMAP_MBOX) += omap-mailbox.o
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
new file mode 100644
index 0000000..3082f08
--- /dev/null
+++ b/drivers/mailbox/mailbox.c
@@ -0,0 +1,534 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/mailbox_client.h>
+#include <linux/mailbox_controller.h>
+
+/*
+ * The length of circular buffer for queuing messages from a client.
+ * 'msg_count' tracks the number of buffered messages while 'msg_free'
+ * is the index where the next message would be buffered.
+ * We shouldn't need it too big because every transferr is interrupt
+ * triggered and if we have lots of data to transfer, the interrupt
+ * latencies are going to be the bottleneck, not the buffer length.
+ * Besides, ipc_send_message could be called from atomic context and
+ * the client could also queue another message from the notifier 'txcb'
+ * of the last transfer done.
+ * REVIST: If too many platforms see the "Try increasing MBOX_TX_QUEUE_LEN"
+ * print, it needs to be taken from config option or somesuch.
+ */
+#define MBOX_TX_QUEUE_LEN 20
+
+#define TXDONE_BY_IRQ (1 << 0) /* controller has remote RTR irq */
+#define TXDONE_BY_POLL (1 << 1) /* controller can read status of last TX */
+#define TXDONE_BY_ACK (1 << 2) /* S/W ACK recevied by Client ticks the TX */
+
+struct ipc_chan {
+ char name[16]; /* link_name */
+ struct ipc_con *con; /* Parent Controller */
+ unsigned txdone_method;
+
+ /* Cached values from controller */
+ struct ipc_link *link;
+ struct ipc_link_ops *link_ops;
+
+ /* Cached values from client */
+ void *cl_id;
+ void (*rxcb)(void *cl_id, void *mssg);
+ void (*txcb)(void *cl_id, void *mssg, enum xfer_result r);
+ bool tx_block;
+ unsigned long tx_tout;
+ struct completion tx_complete;
+
+ void *active_req;
+ unsigned msg_count, msg_free;
+ void *msg_data[MBOX_TX_QUEUE_LEN];
+ bool assigned;
+ /* Serialize access to the channel */
+ spinlock_t lock;
+ /* Hook to add to the controller's list of channels */
+ struct list_head node;
+ /* Notifier to all clients waiting on aquiring this channel */
+ struct blocking_notifier_head avail;
+};
+
+/* Internal representation of a controller */
+struct ipc_con {
+ char name[16]; /* controller_name */
+ struct list_head channels;
+ /*
+ * If the controller supports only TXDONE_BY_POLL,
+ * this timer polls all the links for txdone.
+ */
+ struct timer_list poll;
+ unsigned period;
+ /* Hook to add to the global controller list */
+ struct list_head node;
+};
+
+static LIST_HEAD(ipc_cons);
+static DEFINE_MUTEX(con_mutex);
+
+static request_token_t _add_to_rbuf(struct ipc_chan *chan, void *mssg)
+{
+ request_token_t idx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&chan->lock, flags);
+
+ /* See if there is any space left */
+ if (chan->msg_count == MBOX_TX_QUEUE_LEN) {
+ spin_unlock_irqrestore(&chan->lock, flags);
+ return 0;
+ }
+
+ idx = chan->msg_free;
+ chan->msg_data[idx] = mssg;
+ chan->msg_count++;
+
+ if (idx == MBOX_TX_QUEUE_LEN - 1)
+ chan->msg_free = 0;
+ else
+ chan->msg_free++;
+
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ /* To aid debugging, we return 'idx+1' instead of 1 */
+ return idx + 1;
+}
+
+static void _msg_submit(struct ipc_chan *chan)
+{
+ struct ipc_link *link = chan->link;
+ unsigned count, idx;
+ unsigned long flags;
+ void *data;
+ int err;
+
+ spin_lock_irqsave(&chan->lock, flags);
+
+ if (!chan->msg_count || chan->active_req) {
+ spin_unlock_irqrestore(&chan->lock, flags);
+ return;
+ }
+
+ count = chan->msg_count;
+ idx = chan->msg_free;
+ if (idx >= count)
+ idx -= count;
+ else
+ idx += MBOX_TX_QUEUE_LEN - count;
+
+ data = chan->msg_data[idx];
+
+ /* Try to submit a message to the IPC controller */
+ err = chan->link_ops->send_data(link, data);
+ if (!err) {
+ chan->active_req = data;
+ chan->msg_count--;
+ }
+
+ spin_unlock_irqrestore(&chan->lock, flags);
+}
+
+static void tx_tick(struct ipc_chan *chan, enum xfer_result r)
+{
+ unsigned long flags;
+ void *mssg;
+
+ spin_lock_irqsave(&chan->lock, flags);
+ mssg = chan->active_req;
+ chan->active_req = NULL;
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ /* Submit next message */
+ _msg_submit(chan);
+
+ /* Notify the client */
+ if (chan->tx_block)
+ complete(&chan->tx_complete);
+ else if (mssg && chan->txcb)
+ chan->txcb(chan->cl_id, mssg, r);
+}
+
+static void poll_txdone(unsigned long data)
+{
+ struct ipc_con *con = (struct ipc_con *)data;
+ bool txdone, resched = false;
+ struct ipc_chan *chan;
+
+ list_for_each_entry(chan, &con->channels, node) {
+ if (chan->active_req && chan->assigned) {
+ resched = true;
+ txdone = chan->link_ops->last_tx_done(chan->link);
+ if (txdone)
+ tx_tick(chan, XFER_OK);
+ }
+ }
+
+ if (resched)
+ mod_timer(&con->poll,
+ jiffies + msecs_to_jiffies(con->period));
+}
+
+/*
+ * After 'startup' and before 'shutdown', the IPC controller driver
+ * notifies the API of data received over the link.
+ * The controller driver should make sure the 'RTR' is de-asserted since
+ * reception of the packet and until after this call returns.
+ * This call could be made from atomic context.
+ */
+void ipc_link_received_data(struct ipc_link *link, void *mssg)
+{
+ struct ipc_chan *chan = (struct ipc_chan *)link->api_priv;
+
+ /* No buffering the received data */
+ if (chan->rxcb)
+ chan->rxcb(chan->cl_id, mssg);
+}
+EXPORT_SYMBOL(ipc_link_received_data);
+
+/*
+ * The IPC controller driver notifies the API that the remote has
+ * asserted RTR and it could now send another message on the link.
+ */
+void ipc_link_txdone(struct ipc_link *link, enum xfer_result r)
+{
+ struct ipc_chan *chan = (struct ipc_chan *)link->api_priv;
+
+ if (unlikely(!(chan->txdone_method & TXDONE_BY_IRQ))) {
+ pr_err("Controller can't run the TX ticker\n");
+ return;
+ }
+
+ tx_tick(chan, r);
+}
+EXPORT_SYMBOL(ipc_link_txdone);
+
+/*
+ * The client/protocol had received some 'ACK' packet and it notifies
+ * the API that the last packet was sent successfully. This only works
+ * if the controller doesn't get IRQ for TX done.
+ */
+void ipc_client_txdone(void *channel, enum xfer_result r)
+{
+ struct ipc_chan *chan = (struct ipc_chan *)channel;
+ bool txdone = true;
+
+ if (unlikely(!(chan->txdone_method & TXDONE_BY_ACK))) {
+ pr_err("Client can't run the TX ticker\n");
+ return;
+ }
+
+ if (chan->txdone_method & TXDONE_BY_POLL)
+ txdone = chan->link_ops->last_tx_done(chan->link);
+
+ if (txdone)
+ tx_tick(chan, r);
+}
+EXPORT_SYMBOL(ipc_client_txdone);
+
+/*
+ * Called by a client to "put data on the h/w channel" so that if
+ * everything else is fine we don't need to do anything more locally
+ * for the remote to receive the data intact.
+ * In reality, the remote may receive it intact, corrupted or not at all.
+ * This could be called from atomic context as it simply
+ * queues the data and returns a token (request_token_t)
+ * against the request.
+ * The client is later notified of successful transmission of
+ * data over the channel via the 'txcb'. The client could in
+ * turn queue more messages from txcb.
+ */
+request_token_t ipc_send_message(void *channel, void *mssg)
+{
+ struct ipc_chan *chan = (struct ipc_chan *)channel;
+ request_token_t t;
+
+ if (!chan || !chan->assigned)
+ return 0;
+
+ t = _add_to_rbuf(chan, mssg);
+ if (!t)
+ pr_err("Try increasing MBOX_TX_QUEUE_LEN\n");
+
+ _msg_submit(chan);
+
+ if (chan->txdone_method == TXDONE_BY_POLL)
+ poll_txdone((unsigned long)chan->con);
+
+ if (chan->tx_block && chan->active_req) {
+ int ret;
+ init_completion(&chan->tx_complete);
+ ret = wait_for_completion_timeout(&chan->tx_complete,
+ chan->tx_tout);
+ if (ret == 0) {
+ t = 0;
+ tx_tick(chan, XFER_ERR);
+ }
+ }
+
+ return t;
+}
+EXPORT_SYMBOL(ipc_send_message);
+
+/*
+ * A client driver asks for exclusive use of a channel/mailbox.
+ * If assigned, the channel has to be 'freed' before it could
+ * be assigned to some other client.
+ * After assignment, any packet received on this channel will be
+ * handed over to the client via the 'rxcb' callback.
+ * The 'txcb' callback is used to notify client upon sending the
+ * packet over the channel, which may or may not have been yet
+ * read by the remote processor.
+ */
+void *ipc_request_channel(struct ipc_client *cl)
+{
+ struct ipc_chan *chan;
+ struct ipc_con *con;
+ unsigned long flags;
+ char *con_name;
+ int len, ret;
+
+ con_name = cl->chan_name;
+ len = strcspn(cl->chan_name, ":");
+
+ ret = 0;
+ mutex_lock(&con_mutex);
+ list_for_each_entry(con, &ipc_cons, node)
+ if (!strncmp(con->name, con_name, len)) {
+ ret = 1;
+ break;
+ }
+ mutex_unlock(&con_mutex);
+
+ if (!ret) {
+ pr_info("Channel(%s) not found!\n", cl->chan_name);
+ return NULL;
+ }
+
+ ret = 0;
+ list_for_each_entry(chan, &con->channels, node) {
+ if (!strcmp(con_name + len + 1, chan->name)
+ && !chan->assigned) {
+ spin_lock_irqsave(&chan->lock, flags);
+ chan->msg_free = 0;
+ chan->msg_count = 0;
+ chan->active_req = NULL;
+ chan->rxcb = cl->rxcb;
+ chan->txcb = cl->txcb;
+ chan->cl_id = cl->cl_id;
+ chan->assigned = true;
+ chan->tx_block = cl->tx_block;
+ if (!cl->tx_tout)
+ chan->tx_tout = msecs_to_jiffies(3600000);
+ else
+ chan->tx_tout = msecs_to_jiffies(cl->tx_tout);
+ if (chan->txdone_method == TXDONE_BY_POLL
+ && cl->knows_txdone)
+ chan->txdone_method |= TXDONE_BY_ACK;
+ spin_unlock_irqrestore(&chan->lock, flags);
+ ret = 1;
+ break;
+ }
+ }
+
+ if (!ret) {
+ pr_err("Unable to assign mailbox(%s)\n", cl->chan_name);
+ return NULL;
+ }
+
+ ret = chan->link_ops->startup(chan->link, cl->link_data);
+ if (ret) {
+ pr_err("Unable to startup the link\n");
+ ipc_free_channel((void *)chan);
+ return NULL;
+ }
+
+ return (void *)chan;
+}
+EXPORT_SYMBOL(ipc_request_channel);
+
+/* Drop any messages queued and release the channel */
+void ipc_free_channel(void *ch)
+{
+ struct ipc_chan *chan = (struct ipc_chan *)ch;
+ unsigned long flags;
+
+ if (!chan || !chan->assigned)
+ return;
+
+ chan->link_ops->shutdown(chan->link);
+
+ /* The queued TX requests are simply aborted, no callbacks are made */
+ spin_lock_irqsave(&chan->lock, flags);
+ chan->assigned = false;
+ chan->active_req = NULL;
+ if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
+ chan->txdone_method = TXDONE_BY_POLL;
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ blocking_notifier_call_chain(&chan->avail, 0, NULL);
+}
+EXPORT_SYMBOL(ipc_free_channel);
+
+static struct ipc_chan *name_to_chan(const char *name)
+{
+ struct ipc_chan *chan = NULL;
+ struct ipc_con *con;
+ int len, found = 0;
+
+ len = strcspn(name, ":");
+
+ mutex_lock(&con_mutex);
+
+ list_for_each_entry(con, &ipc_cons, node) {
+ if (!strncmp(con->name, name, len)) {
+ list_for_each_entry(chan, &con->channels, node) {
+ if (!strcmp(name + len + 1, chan->name)) {
+ found = 1;
+ goto done;
+ }
+ }
+ }
+ }
+done:
+ mutex_unlock(&con_mutex);
+
+ if (!found)
+ return NULL;
+
+ return chan;
+}
+
+int ipc_notify_chan_register(const char *name, struct notifier_block *nb)
+{
+ struct ipc_chan *chan = name_to_chan(name);
+
+ if (chan && nb)
+ return blocking_notifier_chain_register(&chan->avail, nb);
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(ipc_notify_chan_register);
+
+void ipc_notify_chan_unregister(const char *name, struct notifier_block *nb)
+{
+ struct ipc_chan *chan = name_to_chan(name);
+
+ if (chan && nb)
+ blocking_notifier_chain_unregister(&chan->avail, nb);
+}
+EXPORT_SYMBOL(ipc_notify_chan_unregister);
+
+/*
+ * Call for IPC controller drivers to register a controller, adding
+ * its channels/mailboxes to the global pool.
+ */
+int ipc_links_register(struct ipc_controller *ipc)
+{
+ int i, num_links, txdone;
+ struct ipc_chan *chan;
+ struct ipc_con *con;
+
+ /* Sanity check */
+ if (!ipc || !ipc->ops)
+ return -EINVAL;
+
+ for (i = 0; ipc->links[i]; i++)
+ ;
+ if (!i)
+ return -EINVAL;
+ num_links = i;
+
+ mutex_lock(&con_mutex);
+ /* Check if already populated */
+ list_for_each_entry(con, &ipc_cons, node)
+ if (!strcmp(ipc->controller_name, con->name)) {
+ mutex_unlock(&con_mutex);
+ return -EINVAL;
+ }
+ mutex_unlock(&con_mutex);
+
+ con = kzalloc(sizeof(*con) + sizeof(*chan) * num_links, GFP_KERNEL);
+ if (!con)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&con->channels);
+ snprintf(con->name, 16, "%s", ipc->controller_name);
+
+ if (ipc->txdone_irq)
+ txdone = TXDONE_BY_IRQ;
+ else if (ipc->txdone_poll)
+ txdone = TXDONE_BY_POLL;
+ else /* It has to be ACK then */
+ txdone = TXDONE_BY_ACK;
+
+ if (txdone == TXDONE_BY_POLL) {
+ con->period = ipc->txpoll_period;
+ con->poll.function = &poll_txdone;
+ con->poll.data = (unsigned long)con;
+ init_timer(&con->poll);
+ }
+
+ chan = (void *)con + sizeof(*con);
+ for (i = 0; i < num_links; i++) {
+ chan[i].con = con;
+ chan[i].assigned = false;
+ chan[i].link_ops = ipc->ops;
+ chan[i].link = ipc->links[i];
+ chan[i].txdone_method = txdone;
+ chan[i].link->api_priv = &chan[i];
+ spin_lock_init(&chan[i].lock);
+ BLOCKING_INIT_NOTIFIER_HEAD(&chan[i].avail);
+ list_add_tail(&chan[i].node, &con->channels);
+ snprintf(chan[i].name, 16, "%s", ipc->links[i]->link_name);
+ }
+
+ mutex_lock(&con_mutex);
+ list_add_tail(&con->node, &ipc_cons);
+ mutex_unlock(&con_mutex);
+
+ return 0;
+}
+EXPORT_SYMBOL(ipc_links_register);
+
+void ipc_links_unregister(struct ipc_controller *ipc)
+{
+ struct ipc_con *t, *con = NULL;
+ struct ipc_chan *chan;
+
+ mutex_lock(&con_mutex);
+
+ list_for_each_entry(t, &ipc_cons, node)
+ if (!strcmp(ipc->controller_name, t->name)) {
+ con = t;
+ break;
+ }
+
+ if (con)
+ list_del(&con->node);
+
+ mutex_unlock(&con_mutex);
+
+ if (!con)
+ return;
+
+ list_for_each_entry(chan, &con->channels, node)
+ ipc_free_channel((void *)chan);
+
+ del_timer_sync(&con->poll);
+
+ kfree(con);
+}
+EXPORT_SYMBOL(ipc_links_unregister);
diff --git a/include/linux/mailbox.h b/include/linux/mailbox.h
new file mode 100644
index 0000000..232e2c4
--- /dev/null
+++ b/include/linux/mailbox.h
@@ -0,0 +1,17 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __MAILBOX_H
+#define __MAILBOX_H
+
+enum xfer_result {
+ XFER_OK = 0,
+ XFER_ERR,
+};
+
+typedef unsigned request_token_t;
+
+#endif /* __MAILBOX_H */
diff --git a/include/linux/mailbox_client.h b/include/linux/mailbox_client.h
new file mode 100644
index 0000000..c43f2c7
--- /dev/null
+++ b/include/linux/mailbox_client.h
@@ -0,0 +1,87 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __MAILBOX_CLIENT_H
+#define __MAILBOX_CLIENT_H
+
+#include <linux/mailbox.h>
+
+/**
+ * struct ipc_client - User of a mailbox
+ * @chan_name: the "controller:channel" this client wants
+ * @cl_id: The identity to associate any tx/rx data with
+ * @rxcb: atomic callback to provide client the data received
+ * @txcb: atomic callback to tell client of data transmission
+ * @tx_block: if the ipc_send_message should block until data is transmitted
+ * @tx_tout: Max block period in ms before TX is assumed failure
+ * @knows_txdone: if the client could run the TX state machine. Usually if
+ * the client receives some ACK packet for transmission. Unused if the
+ * controller already has TX_Done/RTR IRQ.
+ * @link_data: Optional controller specific parameters during channel request
+ */
+struct ipc_client {
+ char *chan_name;
+ void *cl_id;
+ void (*rxcb)(void *cl_id, void *mssg);
+ void (*txcb)(void *cl_id, void *mssg, enum xfer_result r);
+ bool tx_block;
+ unsigned long tx_tout;
+ bool knows_txdone;
+ void *link_data;
+};
+
+/**
+ * The Client specifies its requirements and capabilities while asking for
+ * a channel/mailbox by name. It can't be called from atomic context.
+ * The channel is exclusively allocated and can't be used by another
+ * client before the owner calls ipc_free_channel.
+ */
+void *ipc_request_channel(struct ipc_client *cl);
+
+/**
+ * For client to submit data to the controller destined for a remote
+ * processor. If the client had set 'tx_block', the call will return
+ * either when the remote receives the data or when 'tx_tout' millisecs
+ * run out.
+ * In non-blocking mode, the requests are buffered by the API and a
+ * non-zero token is returned for each queued request. If the queue
+ * was full the returned token will be 0. Upon failure or successful
+ * TX, the API calls 'txcb' from atomic context, from which the client
+ * could submit yet another request.
+ * In blocking mode, 'txcb' is not called, effectively making the
+ * queue length 1. The returned value is 0 if TX timed out, some
+ * non-zero value upon success.
+ */
+request_token_t ipc_send_message(void *channel, void *mssg);
+
+/**
+ * The way for a client to run the TX state machine. This works
+ * only if the client sets 'knows_txdone' and the IPC controller
+ * doesn't get an IRQ for TX_Done/Remote_RTR.
+ */
+void ipc_client_txdone(void *channel, enum xfer_result r);
+
+/**
+ * The client relinquishes control of a mailbox by this call,
+ * make it available to other clients.
+ * The ipc_request/free_channel are light weight calls, so the
+ * client should avoid holding it when it doesn't need to
+ * transfer data.
+ */
+void ipc_free_channel(void *channel);
+
+/**
+ * The client make ask the API to be notified when a particular channel
+ * becomes available to be acquired again.
+ */
+int ipc_notify_chan_register(const char *name, struct notifier_block *nb);
+
+/**
+ * The client is no more interested in acquiring the channel.
+ */
+void ipc_notify_chan_unregister(const char *name, struct notifier_block *nb);
+
+#endif /* __MAILBOX_CLIENT_H */
diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h
new file mode 100644
index 0000000..a907467
--- /dev/null
+++ b/include/linux/mailbox_controller.h
@@ -0,0 +1,102 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __MAILBOX_CONTROLLER_H
+#define __MAILBOX_CONTROLLER_H
+
+#include <linux/mailbox.h>
+
+/**
+ * struct ipc_link - s/w representation of a communication link
+ * @link_name: Literal name assigned to the link. Physically
+ * identical channels may have the same name.
+ * @api_priv: hook for the API to map its private data on the link
+ * Controller driver must not touch it.
+ */
+struct ipc_link {
+ char link_name[16];
+ void *api_priv;
+};
+
+/**
+ * struct ipc_link - s/w representation of a communication link
+ * @send_data: The API asks the IPC controller driver, in atomic
+ * context try to transmit a message on the bus. Returns 0 if
+ * data is accepted for transmission, -EBUSY while rejecting
+ * if the remote hasn't yet read the last data sent. Actual
+ * transmission of data is reported by the controller via
+ * ipc_link_txdone (if it has some TX ACK irq). It must not
+ * block.
+ * @startup: Called when a client requests the link. The controller
+ * could ask clients for additional parameters of communication
+ * to be provided via client's link_data. This call may block.
+ * After this call the Controller must forward any data received
+ * on the link by calling ipc_link_received_data (which won't block)
+ * @shutdown: Called when a client relinquishes control of a link.
+ * This call may block too. The controller must not forwared
+ * any received data anymore.
+ * @last_tx_done: If the controller sets 'txdone_poll', the API calls
+ * this to poll status of last TX. The controller must give priority
+ * to IRQ method over polling and never set both txdone_poll and
+ * txdone_irq. Only in polling mode 'send_data' is expected to
+ * return -EBUSY. Used only if txdone_poll:=true && txdone_irq:=false
+ */
+struct ipc_link_ops {
+ int (*send_data)(struct ipc_link *link, void *data);
+ int (*startup)(struct ipc_link *link, void *params);
+ void (*shutdown)(struct ipc_link *link);
+ bool (*last_tx_done)(struct ipc_link *link);
+};
+
+/**
+ * struct ipc_controller - Controller of a class of communication links
+ * @controller_name: Literal name of the controller.
+ * @ops: Operators that work on each communication link
+ * @links: Null terminated array of links.
+ * @txdone_irq: Indicates if the controller can report to API when the
+ * last transmitted data was read by the remote. Eg, if it has some
+ * TX ACK irq.
+ * @txdone_poll: If the controller can read but not report the TX done.
+ * Eg, is some register shows the TX status but no interrupt rises.
+ * Ignored if 'txdone_irq' is set.
+ * @txpoll_period: If 'txdone_poll' is in effect, the API polls for
+ * last TX's status after these many millisecs
+ */
+struct ipc_controller {
+ char controller_name[16];
+ struct ipc_link_ops *ops;
+ struct ipc_link **links;
+ bool txdone_irq;
+ bool txdone_poll;
+ unsigned txpoll_period;
+};
+
+/**
+ * The controller driver registers its communication links to the
+ * global pool managed by the API.
+ */
+int ipc_links_register(struct ipc_controller *ipc_con);
+
+/**
+ * After startup and before shutdown any data received on the link
+ * is pused to the API via atomic ipc_link_received_data() API.
+ * The controller should ACK the RX only after this call returns.
+ */
+void ipc_link_received_data(struct ipc_link *link, void *data);
+
+/**
+ * The controller the has IRQ for TX ACK calls this atomic API
+ * to tick the TX state machine. It works only if txdone_irq
+ * is set by the controller.
+ */
+void ipc_link_txdone(struct ipc_link *link, enum xfer_result r);
+
+/**
+ * Purge the links from the global pool maintained by the API.
+ */
+void ipc_links_unregister(struct ipc_controller *ipc_con);
+
+#endif /* __MAILBOX_CONTROLLER_H */
--
1.8.1.2