dmi

2019-11-09 17:17:18

字体：大中小

来源：转载

供稿：网友

在arch/arm64/kernel/efi.c 中会对dmi初始化，dmi的全程是Desktop Management Interface.属于smbios的一部分.static int __init arm64_dmi_init(void){ /* * On arm64, DMI depends on UEFI, and dmi_scan_machine() needs to * be called early because dmi_id_init(), which is an arch_initcall * itself, depends on dmi_scan_machine() having been called already. */ dmi_scan_machine(); if (dmi_available) dmi_set_dump_stack_arch_desc(); return 0;}core_initcall(arm64_dmi_init);可见是通过core_initcall(arm64_dmi_init);在kernel 初始化阶段自动运行的.void __init dmi_scan_machine(void){ char __iomem *p, *q; char buf[32]; if (efi_enabled(EFI_CONFIG_TABLES)) { if (efi.smbios3 != EFI_INVALID_TABLE_ADDR) { } if (efi.smbios == EFI_INVALID_TABLE_ADDR) goto error; if (!dmi_PResent(buf)) { dmi_available = 1; goto out; } } else if (IS_ENABLED(CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK)) { } error: pr_info("DMI not present or invalid./n"); out: dmi_initialized = 1;}在dmi_scan_machine 中首先判断 efi.smbios3 != EFI_INVALID_TABLE_ADDR 或者 efi.smbios == EFI_INVALID_TABLE_ADDR，可见dmi是smbios的一部分，且smbios有两个标准smbios 和 smbios3如果条件成立的话就通过memcpy_fromio(buf, p, 32);将32 byte copy到buf中。在dmi_scan_machine 中如果条件不成立，且定义了CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK，就会在0xF0000, 0x10000 这个范围内找dmi的信息。我们之关注efi.smbios3 != EFI_INVALID_TABLE_ADDR 或者 efi.smbios == EFI_INVALID_TABLE_ADDR 成立的情况。然后调用dmi_presentstatic int __init dmi_present(const u8 *buf){ u32 smbios_ver; if (memcmp(buf, "_SM_", 4) == 0 && buf[5] < 32 && dmi_checksum(buf, buf[5])) { smbios_ver = get_unaligned_be16(buf + 6); smbios_entry_point_size = buf[5]; memcpy(smbios_entry_point, buf, smbios_entry_point_size); /* Some BIOS report weird SMBIOS version, fix that up */ switch (smbios_ver) { case 0x021F: case 0x0221: pr_debug("SMBIOS version fixup (2.%d->2.%d)/n", smbios_ver & 0xFF, 3); smbios_ver = 0x0203; break; case 0x0233: pr_debug("SMBIOS version fixup (2.%d->2.%d)/n", 51, 6); smbios_ver = 0x0206; break; } } else { smbios_ver = 0; } buf += 16; if (memcmp(buf, "_DMI_", 5) == 0 && dmi_checksum(buf, 15)) { if (smbios_ver) dmi_ver = smbios_ver; else dmi_ver = (buf[14] & 0xF0) << 4 | (buf[14] & 0x0F); dmi_ver <<= 8; dmi_num = get_unaligned_le16(buf + 12); dmi_len = get_unaligned_le16(buf + 6); dmi_base = get_unaligned_le32(buf + 8); if (dmi_walk_early(dmi_decode) == 0) { if (smbios_ver) { pr_info("SMBIOS %d.%d present./n", dmi_ver >> 16, (dmi_ver >> 8) & 0xFF); } else { smbios_entry_point_size = 15; memcpy(smbios_entry_point, buf, smbios_entry_point_size); pr_info("Legacy DMI %d.%d present./n", dmi_ver >> 16, (dmi_ver >> 8) & 0xFF); } dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string)); printk(KERN_DEBUG "DMI: %s/n", dmi_ids_string); return 0; } } return 1;}在dmi_present 中首先得到smbios_ver ，如果smbios_ver 不是NULL，则dmi_ver就等于smbios_ver。否则dmi_ver 重新计算. if (smbios_ver) dmi_ver = smbios_ver; else dmi_ver = (buf[14] & 0xF0) << 4 | (buf[14] & 0x0F);最后后调用 if (dmi_walk_early(dmi_decode) == 0) {来将dmi中的信息存到kernel中方面其他程序查询.static void __init dmi_decode(const struct dmi_header *dm, void *dummy){ switch (dm->type) { case 0: /* BIOS Information */ dmi_save_ident(dm, DMI_BIOS_VENDOR, 4); dmi_save_ident(dm, DMI_BIOS_VERSION, 5); dmi_save_ident(dm, DMI_BIOS_DATE, 8); break; case 1: /* System Information */ dmi_save_ident(dm, DMI_SYS_VENDOR, 4); dmi_save_ident(dm, DMI_PRODUCT_NAME, 5); dmi_save_ident(dm, DMI_PRODUCT_VERSION, 6); dmi_save_ident(dm, DMI_PRODUCT_SERIAL, 7); dmi_save_uuid(dm, DMI_PRODUCT_UUID, 8); break; case 2: /* Base Board Information */ dmi_save_ident(dm, DMI_BOARD_VENDOR, 4); dmi_save_ident(dm, DMI_BOARD_NAME, 5); dmi_save_ident(dm, DMI_BOARD_VERSION, 6); dmi_save_ident(dm, DMI_BOARD_SERIAL, 7); dmi_save_ident(dm, DMI_BOARD_ASSET_TAG, 8); break; case 3: /* Chassis Information */ dmi_save_ident(dm, DMI_CHASSIS_VENDOR, 4); dmi_save_type(dm, DMI_CHASSIS_TYPE, 5); dmi_save_ident(dm, DMI_CHASSIS_VERSION, 6); dmi_save_ident(dm, DMI_CHASSIS_SERIAL, 7); dmi_save_ident(dm, DMI_CHASSIS_ASSET_TAG, 8); break; case 9: /* System Slots */ dmi_save_system_slot(dm); break; case 10: /* Onboard Devices Information */ dmi_save_devices(dm); break; case 11: /* OEM Strings */ dmi_save_oem_strings_devices(dm); break; case 38: /* ipMI Device Information */ dmi_save_ipmi_device(dm); break; case 41: /* Onboard Devices Extended Information */ dmi_save_extended_devices(dm); }}可见dmi的信息大概分成0/1/2/3/9/10/11/38/41.根据不同的type将信息存到不同的数组中。我们以System Information为例dmi_save_ident(dm, DMI_SYS_VENDOR, 4);static void __init dmi_save_ident(const struct dmi_header *dm, int slot, int string){ const char *d = (const char *) dm; const char *p; if (dmi_ident[slot]) return; p = dmi_string(dm, d[string]); if (p == NULL) return; dmi_ident[slot] = p;}可见是存在dmi_ident这个数组中。这样我们就可以通过dmi_get_system_info 函数从dmi_ident 数组中拿到System Informationconst char *dmi_get_system_info(int field){ return dmi_ident[field];}EXPORT_SYMBOL(dmi_get_system_info);

上一篇：UITabBar 设置选中、未选中状态下title的字体颜色

下一篇：关于APP冷启动与热启动的区别及冷启动出现的白屏解决办法