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| author | Kees Cook <kees+treewide@kernel.org> | 2026-09-02 15:31:14 -0700 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2026-09-04 21:37:00 -0700 |
| commit | 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d (patch) | |
| tree | c65086f9bdcd48c6360fb7cb4598bca084da1f32 /Documentation/driver-api/mailbox.rst | |
| download | linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.tar.gz linux-stable-3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d.zip | |
treewide: refresh kmalloc_obj() conversionsgrafted
This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci
This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.
Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.
Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
Diffstat (limited to 'Documentation/driver-api/mailbox.rst')
| -rw-r--r-- | Documentation/driver-api/mailbox.rst | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/Documentation/driver-api/mailbox.rst b/Documentation/driver-api/mailbox.rst new file mode 100644 index 000000000..d46c60bd5 --- /dev/null +++ b/Documentation/driver-api/mailbox.rst @@ -0,0 +1,129 @@ +============================ +The Common Mailbox Framework +============================ + +:Author: 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. + + + +Controller Driver (See include/linux/mailbox_controller.h) +========================================================== + + +Allocate mbox_controller and the array of mbox_chan. +Populate mbox_chan_ops, except flush() and 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. + + +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_obj(*dc_sync); + dc_async = kzalloc_obj(*dc_async); + + /* 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); + } |
