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 
22 static efi_guid_t screen_info_guid = LINUX_EFI_SCREEN_INFO_TABLE_GUID;
23 
24 struct 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 	status = efi_bs_call(install_configuration_table,
36 			     &screen_info_guid, si);
37 	if (status == EFI_SUCCESS)
38 		return si;
39 
40 	efi_bs_call(free_pool, si);
41 	return NULL;
42 }
43 
44 void free_screen_info(struct screen_info *si)
45 {
46 	if (!si)
47 		return;
48 
49 	efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
50 	efi_bs_call(free_pool, si);
51 }
52