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(s: si, c: 0, n: 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}
54

source code of linux/drivers/firmware/efi/libstub/screen_info.c