1============================ 2The Common Mailbox Framework 3============================ 4 5:Author: Jassi Brar <jaswinder.singh@linaro.org> 6 7This document aims to help developers write client and controller 8drivers for the API. But before we start, let us note that the 9client (especially) and controller drivers are likely going to be 10very platform specific because the remote firmware is likely to be 11proprietary and implement non-standard protocol. So even if two 12platforms employ, say, PL320 controller, the client drivers can't 13be shared across them. Even the PL320 driver might need to accommodate 14some platform specific quirks. So the API is meant mainly to avoid 15similar copies of code written for each platform. Having said that, 16nothing prevents the remote f/w to also be Linux based and use the 17same api there. However none of that helps us locally because we only 18ever deal at client's protocol level. 19 20Some of the choices made during implementation are the result of this 21peculiarity of this "common" framework. 22 23 24 25Controller Driver (See include/linux/mailbox_controller.h) 26========================================================== 27 28 29Allocate mbox_controller and the array of mbox_chan. 30Populate mbox_chan_ops, except peek_data() all are mandatory. 31The controller driver might know a message has been consumed 32by the remote by getting an IRQ or polling some hardware flag 33or it can never know (the client knows by way of the protocol). 34The method in order of preference is IRQ -> Poll -> None, which 35the controller driver should set via 'txdone_irq' or 'txdone_poll' 36or neither. 37 38 39Client Driver (See include/linux/mailbox_client.h) 40================================================== 41 42 43The client might want to operate in blocking mode (synchronously 44send a message through before returning) or non-blocking/async mode (submit 45a message and a callback function to the API and return immediately). 46 47:: 48 49 struct demo_client { 50 struct mbox_client cl; 51 struct mbox_chan *mbox; 52 struct completion c; 53 bool async; 54 /* ... */ 55 }; 56 57 /* 58 * This is the handler for data received from remote. The behaviour is purely 59 * dependent upon the protocol. This is just an example. 60 */ 61 static void message_from_remote(struct mbox_client *cl, void *mssg) 62 { 63 struct demo_client *dc = container_of(cl, struct demo_client, cl); 64 if (dc->async) { 65 if (is_an_ack(mssg)) { 66 /* An ACK to our last sample sent */ 67 return; /* Or do something else here */ 68 } else { /* A new message from remote */ 69 queue_req(mssg); 70 } 71 } else { 72 /* Remote f/w sends only ACK packets on this channel */ 73 return; 74 } 75 } 76 77 static void sample_sent(struct mbox_client *cl, void *mssg, int r) 78 { 79 struct demo_client *dc = container_of(cl, struct demo_client, cl); 80 complete(&dc->c); 81 } 82 83 static void client_demo(struct platform_device *pdev) 84 { 85 struct demo_client *dc_sync, *dc_async; 86 /* The controller already knows async_pkt and sync_pkt */ 87 struct async_pkt ap; 88 struct sync_pkt sp; 89 90 dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL); 91 dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL); 92 93 /* Populate non-blocking mode client */ 94 dc_async->cl.dev = &pdev->dev; 95 dc_async->cl.rx_callback = message_from_remote; 96 dc_async->cl.tx_done = sample_sent; 97 dc_async->cl.tx_block = false; 98 dc_async->cl.tx_tout = 0; /* doesn't matter here */ 99 dc_async->cl.knows_txdone = false; /* depending upon protocol */ 100 dc_async->async = true; 101 init_completion(&dc_async->c); 102 103 /* Populate blocking mode client */ 104 dc_sync->cl.dev = &pdev->dev; 105 dc_sync->cl.rx_callback = message_from_remote; 106 dc_sync->cl.tx_done = NULL; /* operate in blocking mode */ 107 dc_sync->cl.tx_block = true; 108 dc_sync->cl.tx_tout = 500; /* by half a second */ 109 dc_sync->cl.knows_txdone = false; /* depending upon protocol */ 110 dc_sync->async = false; 111 112 /* ASync mailbox is listed second in 'mboxes' property */ 113 dc_async->mbox = mbox_request_channel(&dc_async->cl, 1); 114 /* Populate data packet */ 115 /* ap.xxx = 123; etc */ 116 /* Send async message to remote */ 117 mbox_send_message(dc_async->mbox, &ap); 118 119 /* Sync mailbox is listed first in 'mboxes' property */ 120 dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0); 121 /* Populate data packet */ 122 /* sp.abc = 123; etc */ 123 /* Send message to remote in blocking mode */ 124 mbox_send_message(dc_sync->mbox, &sp); 125 /* At this point 'sp' has been sent */ 126 127 /* Now wait for async chan to be done */ 128 wait_for_completion(&dc_async->c); 129 } 130