mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 17:30:02 +00:00
![Leo Yan](/assets/img/avatar_default.png)
Fix minor typo so that can pass correct pointer variable for container_of(). Signed-off-by: Leo Yan <leo.yan@linaro.org> [jc: tweaked formatting] Signed-off-by: Jonathan Corbet <corbet@lwn.net>
120 lines
4.1 KiB
Text
120 lines
4.1 KiB
Text
The Common Mailbox Framework
|
|
Jassi Brar <jaswinder.singh@linaro.org>
|
|
|
|
This document aims to help developers write client and controller
|
|
drivers for the API. But before we start, let us note that the
|
|
client (especially) and controller drivers are likely going to be
|
|
very platform specific because the remote firmware is likely to be
|
|
proprietary and implement non-standard protocol. So even if two
|
|
platforms employ, say, PL320 controller, the client drivers can't
|
|
be shared across them. Even the PL320 driver might need to accommodate
|
|
some platform specific quirks. So the API is meant mainly to avoid
|
|
similar copies of code written for each platform. Having said that,
|
|
nothing prevents the remote f/w to also be Linux based and use the
|
|
same api there. However none of that helps us locally because we only
|
|
ever deal at client's protocol level.
|
|
Some of the choices made during implementation are the result of this
|
|
peculiarity of this "common" framework.
|
|
|
|
|
|
|
|
Part 1 - Controller Driver (See include/linux/mailbox_controller.h)
|
|
|
|
Allocate mbox_controller and the array of mbox_chan.
|
|
Populate mbox_chan_ops, except peek_data() all are mandatory.
|
|
The controller driver might know a message has been consumed
|
|
by the remote by getting an IRQ or polling some hardware flag
|
|
or it can never know (the client knows by way of the protocol).
|
|
The method in order of preference is IRQ -> Poll -> None, which
|
|
the controller driver should set via 'txdone_irq' or 'txdone_poll'
|
|
or neither.
|
|
|
|
|
|
Part 2 - Client Driver (See include/linux/mailbox_client.h)
|
|
|
|
The client might want to operate in blocking mode (synchronously
|
|
send a message through before returning) or non-blocking/async mode (submit
|
|
a message and a callback function to the API and return immediately).
|
|
|
|
|
|
struct demo_client {
|
|
struct mbox_client cl;
|
|
struct mbox_chan *mbox;
|
|
struct completion c;
|
|
bool async;
|
|
/* ... */
|
|
};
|
|
|
|
/*
|
|
* This is the handler for data received from remote. The behaviour is purely
|
|
* dependent upon the protocol. This is just an example.
|
|
*/
|
|
static void message_from_remote(struct mbox_client *cl, void *mssg)
|
|
{
|
|
struct demo_client *dc = container_of(cl, struct demo_client, cl);
|
|
if (dc->async) {
|
|
if (is_an_ack(mssg)) {
|
|
/* An ACK to our last sample sent */
|
|
return; /* Or do something else here */
|
|
} else { /* A new message from remote */
|
|
queue_req(mssg);
|
|
}
|
|
} else {
|
|
/* Remote f/w sends only ACK packets on this channel */
|
|
return;
|
|
}
|
|
}
|
|
|
|
static void sample_sent(struct mbox_client *cl, void *mssg, int r)
|
|
{
|
|
struct demo_client *dc = container_of(cl, struct demo_client, cl);
|
|
complete(&dc->c);
|
|
}
|
|
|
|
static void client_demo(struct platform_device *pdev)
|
|
{
|
|
struct demo_client *dc_sync, *dc_async;
|
|
/* The controller already knows async_pkt and sync_pkt */
|
|
struct async_pkt ap;
|
|
struct sync_pkt sp;
|
|
|
|
dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL);
|
|
dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL);
|
|
|
|
/* Populate non-blocking mode client */
|
|
dc_async->cl.dev = &pdev->dev;
|
|
dc_async->cl.rx_callback = message_from_remote;
|
|
dc_async->cl.tx_done = sample_sent;
|
|
dc_async->cl.tx_block = false;
|
|
dc_async->cl.tx_tout = 0; /* doesn't matter here */
|
|
dc_async->cl.knows_txdone = false; /* depending upon protocol */
|
|
dc_async->async = true;
|
|
init_completion(&dc_async->c);
|
|
|
|
/* Populate blocking mode client */
|
|
dc_sync->cl.dev = &pdev->dev;
|
|
dc_sync->cl.rx_callback = message_from_remote;
|
|
dc_sync->cl.tx_done = NULL; /* operate in blocking mode */
|
|
dc_sync->cl.tx_block = true;
|
|
dc_sync->cl.tx_tout = 500; /* by half a second */
|
|
dc_sync->cl.knows_txdone = false; /* depending upon protocol */
|
|
dc_sync->async = false;
|
|
|
|
/* ASync mailbox is listed second in 'mboxes' property */
|
|
dc_async->mbox = mbox_request_channel(&dc_async->cl, 1);
|
|
/* Populate data packet */
|
|
/* ap.xxx = 123; etc */
|
|
/* Send async message to remote */
|
|
mbox_send_message(dc_async->mbox, &ap);
|
|
|
|
/* Sync mailbox is listed first in 'mboxes' property */
|
|
dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0);
|
|
/* Populate data packet */
|
|
/* sp.abc = 123; etc */
|
|
/* Send message to remote in blocking mode */
|
|
mbox_send_message(dc_sync->mbox, &sp);
|
|
/* At this point 'sp' has been sent */
|
|
|
|
/* Now wait for async chan to be done */
|
|
wait_for_completion(&dc_async->c);
|
|
}
|