drivers/firmware/efi/libstub/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
  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         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
  46 void 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 }