screen_info.c

 1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <linux/efi.h>
 4#include <linux/screen_info.h>
 5
 6#include <asm/efi.h>
 7
 8#include "efistub.h"
 9
10/*
11 * There are two ways of populating the core kernel's struct screen_info via the stub:
12 * - using a configuration table, like below, which relies on the EFI init code
13 *   to locate the table and copy the contents;
14 * - by linking directly to the core kernel's copy of the global symbol.
15 *
16 * The latter is preferred because it makes the EFIFB earlycon available very
17 * early, but it only works if the EFI stub is part of the core kernel image
18 * itself. The zboot decompressor can only use the configuration table
19 * approach.
20 */
21
22static efi_guid_t screen_info_guid = LINUX_EFI_SCREEN_INFO_TABLE_GUID;
23
24struct screen_info *__alloc_screen_info(void)
25{
26	struct screen_info *si;
27	efi_status_t status;
28
29	status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
30			     sizeof(*si), (void **)&si);
31
32	if (status != EFI_SUCCESS)
33		return NULL;
34
35	memset(si, 0, sizeof(*si));
36
37	status = efi_bs_call(install_configuration_table,
38			     &screen_info_guid, si);
39	if (status == EFI_SUCCESS)
40		return si;
41
42	efi_bs_call(free_pool, si);
43	return NULL;
44}
45
46void free_screen_info(struct screen_info *si)
47{
48	if (!si)
49		return;
50
51	efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
52	efi_bs_call(free_pool, si);
53}