lib/efi_loader/efi_android_boot.c

/*
 * Copyright (c) 2024 The Fuchsia Authors
 *
 * SPDX-License-Identifier:	BSD-3-Clause
 */

#include <common.h>
#include <efi_loader.h>
#include <log.h>
#include <asm/global_data.h>
#include <efi_android_boot.h>
#include <g_dnl.h>
#include <fastboot_usb.h>

DECLARE_GLOBAL_DATA_PTR;

static const efi_guid_t efi_guid_android_boot_protocol =
	EFI_ANDROID_BOOT_PROTOCOL_GUID;

static struct android_boot_protocol_instance {
	efi_android_boot_protocol protocol;
	struct efi_event *timer_event;
	size_t max_out_req_length;
	bool send_completion_already_signaled;
} android_boot;

// USB driver requires a mandatory callback. We simply use a noop placeholder.
// The implementation polls send/receive status directly.
static void noop_cb(struct usb_ep *, struct usb_request *)
{
}

// Checks whether Fastboot USB endpoints are allocated.
static bool is_started(void)
{
	return fastboot_func && fastboot_func->in_ep && fastboot_func->out_ep;
}

static efi_status_t EFIAPI fastboot_usb_interface_start(
	struct efi_android_boot_protocol *self, size_t *max_packet_size)
{
	EFI_ENTRY("%p, %p", self, max_packet_size);

	if (is_started()) {
		return EFI_EXIT(EFI_ALREADY_STARTED);
	} else if (!max_packet_size) {
		return EFI_EXIT(EFI_INVALID_PARAMETER);
	}

	int ret = set_fastboot_usb_completion_cb(noop_cb, noop_cb);
	if (ret) {
		printf("usb_dnl_fastboot failed to set cb: %d\n", ret);
		return EFI_EXIT(EFI_DEVICE_ERROR);
	}

	ret = g_dnl_register("usb_dnl_fastboot");
	if (ret) {
		printf("usb_dnl_fastboot register failed: %d\n", ret);
		return EFI_EXIT(EFI_DEVICE_ERROR);
	}

	if (!is_started()) {
		printf("Fastboot end points not allocated\n");
		return EFI_EXIT(EFI_DEVICE_ERROR);
	}

	*max_packet_size = fastboot_func->in_ep->maxpacket;
	android_boot.max_out_req_length = fastboot_func->out_req->length;
	return EFI_EXIT(EFI_SUCCESS);
}

static efi_status_t EFIAPI
fastboot_usb_interface_stop(struct efi_android_boot_protocol *self)
{
	EFI_ENTRY("%p", self);

	if (!is_started()) {
		return EFI_EXIT(EFI_NOT_STARTED);
	}

	g_dnl_unregister();
	run_command("usb reset", 0);
	reset_fastboot_usb_completion_cb();
	return EFI_EXIT(EFI_SUCCESS);
}

static efi_status_t EFIAPI
fastboot_usb_receive(struct efi_android_boot_protocol *self,
		     size_t *buffer_size, void *buffer)
{
	EFI_ENTRY("%p, %p", buffer_size, buffer);

	if (!is_started()) {
		return EFI_EXIT(EFI_NOT_STARTED);
	}

	// Executes any event check and notification payload. This includes our
	// `efi_fastboot_usb_timer_notify` notify function.
	efi_timer_check();

	if (!fastboot_func->out_req ||
	    fastboot_func->out_req->status == -EINPROGRESS) {
		// Not initialized or the out request packet is queued and busy.
		return EFI_EXIT(EFI_NOT_READY);
	} else if (fastboot_func->out_req->status != 0) {
		// The out request has encountered an error
		return EFI_EXIT(EFI_DEVICE_ERROR);
	} else if (fastboot_func->out_req->actual) {
		// Has available data.
		if (*buffer_size < (size_t)fastboot_func->out_req->actual) {
			// We don't support partial read, the caller has to read the whole
			// packet it previously requested.
			*buffer_size = (size_t)fastboot_func->out_req->actual;
			return EFI_EXIT(EFI_BUFFER_TOO_SMALL);
		}
		memcpy(buffer, fastboot_func->out_req->buf,
		       (size_t)fastboot_func->out_req->actual);
		*buffer_size = (size_t)fastboot_func->out_req->actual;
		// Clear the `actual` field to indicate idleness.
		fastboot_func->out_req->actual = 0;
		return EFI_EXIT(EFI_SUCCESS);
	} else {
		// Usb receive request is not queued yet. Queue it.
		// Adjusts the request length to be the smaller between the maximum
		// length and the requested read size, round up to the multiple of max
		// packet size. This is necessary otherwise if host sends smaller than
		// length amount of data, and it is a multiple of max packet size,
		// driver hangs.
		size_t length =
			min(*buffer_size, android_boot.max_out_req_length);
		length = (length + (fastboot_func->out_ep->maxpacket - 1)) /
			 fastboot_func->out_ep->maxpacket *
			 fastboot_func->out_ep->maxpacket;
		fastboot_func->out_req->length = length;
		if (usb_ep_queue(fastboot_func->out_ep, fastboot_func->out_req,
				 0)) {
			return EFI_EXIT(EFI_DEVICE_ERROR);
		}
		return EFI_EXIT(EFI_NOT_READY);
	}
}

static efi_status_t EFIAPI
fastboot_usb_send(struct efi_android_boot_protocol *self, size_t *buffer_size,
		  const void *buffer)
{
	EFI_ENTRY("%p, %p", buffer_size, buffer);

	if (!is_started()) {
		return EFI_EXIT(EFI_NOT_STARTED);
	}

	// Executes any event check and notification payload. This includes our
	// `efi_fastboot_usb_timer_notify` notify function.
	efi_timer_check();

	if (!fastboot_func->in_req &&
	    fastboot_func->in_req->status == -EINPROGRESS) {
		return EFI_EXIT(EFI_NOT_READY);
	} else if (fastboot_func->in_req->status != 0) {
		return EFI_EXIT(EFI_DEVICE_ERROR);
	} else if (*buffer_size > (size_t)fastboot_func->in_ep->maxpacket) {
		*buffer_size = (size_t)fastboot_func->in_ep->maxpacket;
		return EFI_EXIT(EFI_BAD_BUFFER_SIZE);
	}

	// Resets event signal state.
	android_boot.send_completion_already_signaled = false;
	self->wait_for_send_completion->is_signaled = false;
	memcpy(fastboot_func->in_req->buf, buffer, *buffer_size);
	fastboot_func->in_req->length = *buffer_size;
	if (usb_ep_queue(fastboot_func->in_ep, fastboot_func->in_req, 0)) {
		return EFI_EXIT(EFI_DEVICE_ERROR);
	}
	return EFI_EXIT(EFI_SUCCESS);
}

static struct android_boot_protocol_instance android_boot = {
    .protocol = {
        .revision = EFI_ANDROID_BOOT_PROTOCOL_REVISION,
        .fastboot_usb_interface_start = fastboot_usb_interface_start,
        .fastboot_usb_interface_stop = fastboot_usb_interface_stop,
        .fastboot_usb_receive = fastboot_usb_receive,
        .fastboot_usb_send = fastboot_usb_send,
        .wait_for_send_completion = NULL,
    },
    .timer_event = NULL,
    .send_completion_already_signaled = false,
};

// A timer event notification function that polls send/receive status and
// signals event.
static void EFIAPI efi_fastboot_usb_timer_notify(struct efi_event *event,
						 void *context)
{
	EFI_ENTRY("%p, %p", event, context);
	efi_android_boot_protocol *protocol = &android_boot.protocol;
	if (!is_started() || !protocol->wait_for_send_completion) {
		EFI_EXIT(EFI_SUCCESS);
		return;
	}

	usb_gadget_handle_interrupts();
	if (fastboot_func->in_req->status == 0 &&
	    !android_boot.send_completion_already_signaled) {
		android_boot.send_completion_already_signaled = true;
		protocol->wait_for_send_completion->is_signaled = true;
	}
	EFI_EXIT(EFI_SUCCESS);
}

static void EFIAPI efi_fastboot_usb_wait_notify(struct efi_event *, void *)
{
	// Nothing to do for `wait_for_send_completion` notificiaiton. But UEFI
	// still requires it.
}

// Registers EFI_ANDROID_BOOT_PROTOCOL
efi_status_t efi_android_boot_register(void)
{
	efi_status_t ret = efi_add_protocol(efi_root,
					    &efi_guid_android_boot_protocol,
					    (void *)&android_boot.protocol);
	if (ret != EFI_SUCCESS)
		printf("Cannot install EFI_ANDROID_BOOT_PROTOCOL\n");

	// Create a `wait_for_send_completion` event.
	ret = efi_create_event(EVT_NOTIFY_WAIT, TPL_CALLBACK,
			       efi_fastboot_usb_wait_notify, NULL, NULL,
			       &android_boot.protocol.wait_for_send_completion);
	if (ret != EFI_SUCCESS) {
		printf("Failed to create wait_for_send_completion event\n");
		return ret;
	}

	// Create a timer event so that the notify function can get triggered
	// whenever the EFI boot service processes any event.
	ret = efi_create_event(EVT_TIMER | EVT_NOTIFY_SIGNAL, TPL_NOTIFY,
			       efi_fastboot_usb_timer_notify, NULL, NULL,
			       &android_boot.timer_event);
	if (ret != EFI_SUCCESS) {
		printf("Failed to add EFI_ANDROID_BOOT_PROTOCOL timer event\n");
		return ret;
	}
	// Fastboot USB is time critical, Triggers the event in every timer cycle
	// Set timer period to 0. This is equivalent to invoking
	// `efi_fastboot_usb_timer_notify` every time boot service check any event
	// i.e. in `efi_timer_check()`
	ret = efi_set_timer(android_boot.timer_event, EFI_TIMER_PERIODIC, 0);
	if (ret != EFI_SUCCESS) {
		printf("Failed to set EFI_ANDROID_BOOT_PROTOCOL timer\n");
		return ret;
	}

	return EFI_SUCCESS;
}