diff --git a/fastboot/bootimg_utils.cpp b/fastboot/bootimg_utils.cpp
index 23443ec..feacaa1 100644
--- a/fastboot/bootimg_utils.cpp
+++ b/fastboot/bootimg_utils.cpp
@@ -34,16 +34,15 @@
 #include <stdlib.h>
 #include <string.h>
 
-void bootimg_set_cmdline(boot_img_hdr_v1* h, const char* cmdline) {
-    if (strlen(cmdline) >= sizeof(h->cmdline)) die("command line too large: %zu", strlen(cmdline));
-    strcpy(reinterpret_cast<char*>(h->cmdline), cmdline);
+void bootimg_set_cmdline(boot_img_hdr_v1* h, const std::string& cmdline) {
+    if (cmdline.size() >= sizeof(h->cmdline)) die("command line too large: %zu", cmdline.size());
+    strcpy(reinterpret_cast<char*>(h->cmdline), cmdline.c_str());
 }
 
-boot_img_hdr_v1* mkbootimg(void* kernel, int64_t kernel_size, off_t kernel_offset, void* ramdisk,
-                           int64_t ramdisk_size, off_t ramdisk_offset, void* second,
-                           int64_t second_size, off_t second_offset, size_t page_size, size_t base,
-                           off_t tags_offset, uint32_t header_version, int64_t* bootimg_size) {
-    size_t page_mask = page_size - 1;
+boot_img_hdr_v1* mkbootimg(void* kernel, int64_t kernel_size, void* ramdisk, int64_t ramdisk_size,
+                           void* second, int64_t second_size, size_t base,
+                           const boot_img_hdr_v1& src, int64_t* bootimg_size) {
+    const size_t page_mask = src.page_size - 1;
 
     int64_t header_actual = sizeof(boot_img_hdr_v1) & (~page_mask);
     int64_t kernel_actual = (kernel_size + page_mask) & (~page_mask);
@@ -53,30 +52,26 @@
     *bootimg_size = header_actual + kernel_actual + ramdisk_actual + second_actual;
 
     boot_img_hdr_v1* hdr = reinterpret_cast<boot_img_hdr_v1*>(calloc(*bootimg_size, 1));
-    if (hdr == nullptr) {
-        return hdr;
-    }
+    if (hdr == nullptr) die("couldn't allocate boot image: %" PRId64 " bytes", *bootimg_size);
 
+    *hdr = src;
     memcpy(hdr->magic, BOOT_MAGIC, BOOT_MAGIC_SIZE);
 
     hdr->kernel_size =  kernel_size;
     hdr->ramdisk_size = ramdisk_size;
     hdr->second_size =  second_size;
 
-    hdr->kernel_addr =  base + kernel_offset;
-    hdr->ramdisk_addr = base + ramdisk_offset;
-    hdr->second_addr =  base + second_offset;
-    hdr->tags_addr =    base + tags_offset;
+    hdr->kernel_addr += base;
+    hdr->ramdisk_addr += base;
+    hdr->second_addr += base;
+    hdr->tags_addr += base;
 
-    hdr->page_size =    page_size;
-
-    if (header_version) {
-        hdr->header_version = header_version;
+    if (hdr->header_version != 0) {
         hdr->header_size = sizeof(boot_img_hdr_v1);
     }
 
-    memcpy(hdr->magic + page_size, kernel, kernel_size);
-    memcpy(hdr->magic + page_size + kernel_actual, ramdisk, ramdisk_size);
-    memcpy(hdr->magic + page_size + kernel_actual + ramdisk_actual, second, second_size);
+    memcpy(hdr->magic + hdr->page_size, kernel, kernel_size);
+    memcpy(hdr->magic + hdr->page_size + kernel_actual, ramdisk, ramdisk_size);
+    memcpy(hdr->magic + hdr->page_size + kernel_actual + ramdisk_actual, second, second_size);
     return hdr;
 }
diff --git a/fastboot/bootimg_utils.h b/fastboot/bootimg_utils.h
index d3993f5..fe805b0 100644
--- a/fastboot/bootimg_utils.h
+++ b/fastboot/bootimg_utils.h
@@ -26,17 +26,15 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _FASTBOOT_BOOTIMG_UTILS_H_
-#define _FASTBOOT_BOOTIMG_UTILS_H_
+#pragma once
 
 #include <bootimg.h>
 #include <inttypes.h>
 #include <sys/types.h>
 
-void bootimg_set_cmdline(boot_img_hdr_v1* h, const char* cmdline);
-boot_img_hdr_v1* mkbootimg(void* kernel, int64_t kernel_size, off_t kernel_offset, void* ramdisk,
-                           int64_t ramdisk_size, off_t ramdisk_offset, void* second,
-                           int64_t second_size, off_t second_offset, size_t page_size, size_t base,
-                           off_t tags_offset, uint32_t header_version, int64_t* bootimg_size);
+#include <string>
 
-#endif
+boot_img_hdr_v1* mkbootimg(void* kernel, int64_t kernel_size, void* ramdisk, int64_t ramdisk_size,
+                           void* second, int64_t second_size, size_t base,
+                           const boot_img_hdr_v1& src, int64_t* bootimg_size);
+void bootimg_set_cmdline(boot_img_hdr_v1* h, const std::string& cmdline);
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 4f0b5eb..cf130c9 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -76,9 +76,9 @@
 char cur_product[FB_RESPONSE_SZ + 1];
 
 static const char* serial = nullptr;
-static const char* cmdline = nullptr;
+
 static unsigned short vendor_id = 0;
-static int long_listing = 0;
+static bool g_long_listing = false;
 // Don't resparse files in too-big chunks.
 // libsparse will support INT_MAX, but this results in large allocations, so
 // let's keep it at 1GB to avoid memory pressure on the host.
@@ -86,12 +86,9 @@
 static int64_t sparse_limit = -1;
 static int64_t target_sparse_limit = -1;
 
-static unsigned page_size = 2048;
-static unsigned base_addr      = 0x10000000;
-static unsigned kernel_offset  = 0x00008000;
-static unsigned ramdisk_offset = 0x01000000;
-static unsigned second_offset  = 0x00f00000;
-static unsigned tags_offset    = 0x00000100;
+static unsigned g_base_addr = 0x10000000;
+static boot_img_hdr_v1 g_boot_img_hdr = {};
+static std::string g_cmdline;
 
 static bool g_disable_verity = false;
 static bool g_disable_verification = false;
@@ -223,7 +220,7 @@
             serial = "????????????";
         }
         // output compatible with "adb devices"
-        if (!long_listing) {
+        if (!g_long_listing) {
             printf("%s\tfastboot", serial.c_str());
         } else {
             printf("%-22s fastboot", serial.c_str());
@@ -360,14 +357,18 @@
             "                            Download and boot kernel from RAM.\n"
             " flash:raw PARTITION KERNEL [RAMDISK [SECOND]]\n"
             "                            Create boot image and flash it.\n"
-            // TODO: give -c a long option, and remove the short options for this group?
-            " -c CMDLINE                 Override kernel command line.\n"
+            " --cmdline CMDLINE          Override kernel command line.\n"
             " --base ADDRESS             Set kernel base address (default: 0x10000000).\n"
             " --kernel-offset            Set kernel offset (default: 0x00008000).\n"
             " --ramdisk-offset           Set ramdisk offset (default: 0x01000000).\n"
             " --tags-offset              Set tags offset (default: 0x00000100).\n"
             " --page-size BYTES          Set flash page size (default: 2048).\n"
             " --header-version VERSION   Set boot image header version.\n"
+            " --os-version MAJOR[.MINOR[.PATCH]]\n"
+            "                            Set boot image OS version (default: 0.0.0).\n"
+            " --os-patch-level YYYY-MM-DD\n"
+            "                            Set boot image OS security patch level.\n"
+            // TODO: still missing: `second_addr`, `name`, `id`, `recovery_dtbo_*`.
             "\n"
             // TODO: what device(s) used this? is there any documentation?
             //" continue                               Continue with autoboot.\n"
@@ -404,8 +405,7 @@
 }
 
 static void* load_bootable_image(const std::string& kernel, const std::string& ramdisk,
-                                 const std::string& second_stage, int64_t* sz,
-                                 const char* cmdline, uint32_t header_version) {
+                                 const std::string& second_stage, int64_t* sz) {
     int64_t ksize;
     void* kdata = load_file(kernel.c_str(), &ksize);
     if (kdata == nullptr) die("cannot load '%s': %s", kernel.c_str(), strerror(errno));
@@ -415,12 +415,14 @@
         die("cannot load '%s': too short", kernel.c_str());
     }
     if (!memcmp(kdata, BOOT_MAGIC, BOOT_MAGIC_SIZE)) {
-        if (cmdline) bootimg_set_cmdline(reinterpret_cast<boot_img_hdr_v1*>(kdata), cmdline);
+        if (!g_cmdline.empty()) {
+            bootimg_set_cmdline(reinterpret_cast<boot_img_hdr_v1*>(kdata), g_cmdline);
+        }
         uint32_t header_version_existing =
                 reinterpret_cast<boot_img_hdr_v1*>(kdata)->header_version;
-        if (header_version != header_version_existing) {
+        if (g_boot_img_hdr.header_version != header_version_existing) {
             die("header version mismatch, expected: %" PRIu32 " found %" PRIu32 "",
-                header_version, header_version_existing);
+                g_boot_img_hdr.header_version, header_version_existing);
         }
 
         if (!ramdisk.empty()) die("cannot boot a boot.img *and* ramdisk");
@@ -444,16 +446,12 @@
     }
 
     fprintf(stderr,"creating boot image...\n");
-    int64_t bsize = 0;
-    boot_img_hdr_v1* bdata = mkbootimg(kdata, ksize, kernel_offset,
-                      rdata, rsize, ramdisk_offset,
-                      sdata, ssize, second_offset,
-                      page_size, base_addr, tags_offset, header_version, &bsize);
+    boot_img_hdr_v1* bdata = mkbootimg(kdata, ksize, rdata, rsize, sdata, ssize,
+                                       g_base_addr, g_boot_img_hdr, sz);
     if (bdata == nullptr) die("failed to create boot.img");
 
-    if (cmdline) bootimg_set_cmdline(bdata, cmdline);
-    fprintf(stderr, "creating boot image - %" PRId64 " bytes\n", bsize);
-    *sz = bsize;
+    if (!g_cmdline.empty()) bootimg_set_cmdline(bdata, g_cmdline);
+    fprintf(stderr, "creating boot image - %" PRId64 " bytes\n", *sz);
 
     return bdata;
 }
@@ -1422,34 +1420,37 @@
     bool skip_secondary = false;
     bool set_fbe_marker = false;
     void *data;
-    uint32_t header_version = 0;
     int64_t sz;
     int longindex;
     std::string slot_override;
     std::string next_active;
 
+    g_boot_img_hdr.kernel_addr = 0x00008000;
+    g_boot_img_hdr.ramdisk_addr = 0x01000000;
+    g_boot_img_hdr.second_addr = 0x00f00000;
+    g_boot_img_hdr.tags_addr = 0x00000100;
+    g_boot_img_hdr.page_size = 2048;
+
     const struct option longopts[] = {
-        {"base", required_argument, 0, 'b'},
-        {"kernel_offset", required_argument, 0, 'k'},
-        {"kernel-offset", required_argument, 0, 'k'},
-        {"page_size", required_argument, 0, 'n'},
-        {"page-size", required_argument, 0, 'n'},
-        {"ramdisk_offset", required_argument, 0, 'r'},
-        {"ramdisk-offset", required_argument, 0, 'r'},
-        {"tags_offset", required_argument, 0, 't'},
-        {"tags-offset", required_argument, 0, 't'},
+        {"base", required_argument, 0, 0},
+        {"cmdline", required_argument, 0, 0},
+        {"disable-verification", no_argument, 0, 0},
+        {"disable-verity", no_argument, 0, 0},
+        {"header-version", required_argument, 0, 0},
         {"help", no_argument, 0, 'h'},
-        {"unbuffered", no_argument, 0, 0},
-        {"slot", required_argument, 0, 0},
-        {"set_active", optional_argument, 0, 'a'},
+        {"kernel-offset", required_argument, 0, 0},
+        {"os-patch-level", required_argument, 0, 0},
+        {"os-version", required_argument, 0, 0},
+        {"page-size", required_argument, 0, 0},
+        {"ramdisk-offset", required_argument, 0, 0},
         {"set-active", optional_argument, 0, 'a'},
-        {"skip-secondary", no_argument, 0, 0},
         {"skip-reboot", no_argument, 0, 0},
+        {"skip-secondary", no_argument, 0, 0},
+        {"slot", required_argument, 0, 0},
+        {"tags-offset", required_argument, 0, 0},
+        {"unbuffered", no_argument, 0, 0},
         {"verbose", no_argument, 0, 'v'},
         {"version", no_argument, 0, 0},
-        {"disable-verity", no_argument, 0, 0},
-        {"disable-verification", no_argument, 0, 0},
-        {"header-version", required_argument, 0, 0},
 #if !defined(_WIN32)
         {"wipe-and-use-fbe", no_argument, 0, 0},
 #endif
@@ -1458,98 +1459,108 @@
 
     serial = getenv("ANDROID_SERIAL");
 
-    while (1) {
-        int c = getopt_long(argc, argv, "vwb:k:n:r:t:s:S:lc:i:m:ha::", longopts, &longindex);
-        if (c < 0) {
-            break;
-        }
-        /* Alphabetical cases */
-        switch (c) {
-        case 'a':
-            wants_set_active = true;
-            if (optarg)
-                next_active = optarg;
-            break;
-        case 'b':
-            base_addr = strtoul(optarg, 0, 16);
-            break;
-        case 'c':
-            cmdline = optarg;
-            break;
-        case 'h':
-            return show_help();
-        case 'i': {
-                char *endptr = nullptr;
-                unsigned long val;
-
-                val = strtoul(optarg, &endptr, 0);
-                if (!endptr || *endptr != '\0' || (val & ~0xffff))
-                    die("invalid vendor id '%s'", optarg);
-                vendor_id = (unsigned short)val;
-                break;
-            }
-        case 'k':
-            kernel_offset = strtoul(optarg, 0, 16);
-            break;
-        case 'l':
-            long_listing = 1;
-            break;
-        case 'n':
-            page_size = (unsigned)strtoul(optarg, nullptr, 0);
-            if (!page_size) die("invalid page size");
-            break;
-        case 'r':
-            ramdisk_offset = strtoul(optarg, 0, 16);
-            break;
-        case 't':
-            tags_offset = strtoul(optarg, 0, 16);
-            break;
-        case 's':
-            serial = optarg;
-            break;
-        case 'S':
-            sparse_limit = parse_num(optarg);
-            if (sparse_limit < 0) die("invalid sparse limit");
-            break;
-        case 'v':
-            set_verbose();
-            break;
-        case 'w':
-            wants_wipe = true;
-            break;
-        case '?':
-            return 1;
-        case 0:
-            if (strcmp("unbuffered", longopts[longindex].name) == 0) {
+    int c;
+    while ((c = getopt_long(argc, argv, "a::hi:ls:S:vw", longopts, &longindex)) != -1) {
+        if (c == 0) {
+            std::string name{longopts[longindex].name};
+            if (name == "base") {
+                g_base_addr = strtoul(optarg, 0, 16);
+            } else if (name == "cmdline") {
+                g_cmdline = optarg;
+            } else if (name == "disable-verification") {
+                g_disable_verification = true;
+            } else if (name == "disable-verity") {
+                g_disable_verity = true;
+            } else if (name == "header-version") {
+                g_boot_img_hdr.header_version = strtoul(optarg, nullptr, 0);
+            } else if (name == "kernel-offset") {
+                g_boot_img_hdr.kernel_addr = strtoul(optarg, 0, 16);
+            } else if (name == "os-patch-level") {
+                unsigned year, month, day;
+                if (sscanf(optarg, "%u-%u-%u", &year, &month, &day) != 3) {
+                    syntax_error("OS patch level should be YYYY-MM-DD: %s", optarg);
+                }
+                if (year < 2000 || year >= 2128) syntax_error("year out of range: %d", year);
+                if (month < 1 || month > 12) syntax_error("month out of range: %d", month);
+                g_boot_img_hdr.SetOsPatchLevel(year, month);
+            } else if (name == "os-version") {
+                unsigned major = 0, minor = 0, patch = 0;
+                std::vector<std::string> versions = android::base::Split(optarg, ".");
+                if (versions.size() < 1 || versions.size() > 3 ||
+                    (versions.size() >= 1 && !android::base::ParseUint(versions[0], &major)) ||
+                    (versions.size() >= 2 && !android::base::ParseUint(versions[1], &minor)) ||
+                    (versions.size() == 3 && !android::base::ParseUint(versions[2], &patch)) ||
+                    (major > 0x7f || minor > 0x7f || patch > 0x7f)) {
+                    syntax_error("bad OS version: %s", optarg);
+                }
+                g_boot_img_hdr.SetOsVersion(major, minor, patch);
+            } else if (name == "page-size") {
+                g_boot_img_hdr.page_size = strtoul(optarg, nullptr, 0);
+                if (g_boot_img_hdr.page_size == 0) die("invalid page size");
+            } else if (name == "ramdisk-offset") {
+                g_boot_img_hdr.ramdisk_addr = strtoul(optarg, 0, 16);
+            } else if (name == "skip-reboot") {
+                skip_reboot = true;
+            } else if (name == "skip-secondary") {
+                skip_secondary = true;
+            } else if (name == "slot") {
+                slot_override = optarg;
+            } else if (name == "tags-offset") {
+                g_boot_img_hdr.tags_addr = strtoul(optarg, 0, 16);
+            } else if (name == "unbuffered") {
                 setvbuf(stdout, nullptr, _IONBF, 0);
                 setvbuf(stderr, nullptr, _IONBF, 0);
-            } else if (strcmp("version", longopts[longindex].name) == 0) {
+            } else if (name == "version") {
                 fprintf(stdout, "fastboot version %s\n", FASTBOOT_VERSION);
                 fprintf(stdout, "Installed as %s\n", android::base::GetExecutablePath().c_str());
                 return 0;
-            } else if (strcmp("slot", longopts[longindex].name) == 0) {
-                slot_override = std::string(optarg);
-            } else if (strcmp("skip-secondary", longopts[longindex].name) == 0 ) {
-                skip_secondary = true;
-            } else if (strcmp("skip-reboot", longopts[longindex].name) == 0 ) {
-                skip_reboot = true;
-            } else if (strcmp("disable-verity", longopts[longindex].name) == 0 ) {
-                g_disable_verity = true;
-            } else if (strcmp("disable-verification", longopts[longindex].name) == 0 ) {
-                g_disable_verification = true;
 #if !defined(_WIN32)
-            } else if (strcmp("wipe-and-use-fbe", longopts[longindex].name) == 0) {
+            } else if (name == "wipe-and-use-fbe") {
                 wants_wipe = true;
                 set_fbe_marker = true;
 #endif
-            } else if (strcmp("header-version", longopts[longindex].name) == 0) {
-                header_version = strtoul(optarg, nullptr, 0);
             } else {
                 die("unknown option %s", longopts[longindex].name);
             }
-            break;
-        default:
-            abort();
+        } else {
+            switch (c) {
+                case 'a':
+                    wants_set_active = true;
+                    if (optarg) next_active = optarg;
+                    break;
+                case 'h':
+                    return show_help();
+                case 'i':
+                    {
+                        char *endptr = nullptr;
+                        unsigned long val = strtoul(optarg, &endptr, 0);
+                        if (!endptr || *endptr != '\0' || (val & ~0xffff)) {
+                            die("invalid vendor id '%s'", optarg);
+                        }
+                        vendor_id = (unsigned short)val;
+                        break;
+                    }
+                case 'l':
+                    g_long_listing = true;
+                    break;
+                case 's':
+                    serial = optarg;
+                    break;
+                case 'S':
+                    sparse_limit = parse_num(optarg);
+                    if (sparse_limit < 0) die("invalid sparse limit");
+                    break;
+                case 'v':
+                    set_verbose();
+                    break;
+                case 'w':
+                    wants_wipe = true;
+                    break;
+                case '?':
+                    return 1;
+                default:
+                    abort();
+            }
         }
     }
 
@@ -1668,7 +1679,7 @@
             std::string second_stage;
             if (!args.empty()) second_stage = next_arg(&args);
 
-            data = load_bootable_image(kernel, ramdisk, second_stage, &sz, cmdline, header_version);
+            data = load_bootable_image(kernel, ramdisk, second_stage, &sz);
             fb_queue_download("boot.img", data, sz);
             fb_queue_command("boot", "booting");
         } else if (command == "flash") {
@@ -1694,7 +1705,7 @@
             std::string second_stage;
             if (!args.empty()) second_stage = next_arg(&args);
 
-            data = load_bootable_image(kernel, ramdisk, second_stage, &sz, cmdline, header_version);
+            data = load_bootable_image(kernel, ramdisk, second_stage, &sz);
             auto flashraw = [&](const std::string& partition) {
                 fb_queue_flash(partition, data, sz);
             };
diff --git a/mkbootimg/include/bootimg/bootimg.h b/mkbootimg/include/bootimg/bootimg.h
index 4311b46..406e208 100644
--- a/mkbootimg/include/bootimg/bootimg.h
+++ b/mkbootimg/include/bootimg/bootimg.h
@@ -1,37 +1,33 @@
-/* tools/mkbootimg/bootimg.h
-**
-** Copyright 2007, The Android Open Source Project
-**
-** Licensed under the Apache License, Version 2.0 (the "License");
-** you may not use this file except in compliance with the License.
-** You may obtain a copy of the License at
-**
-**     http://www.apache.org/licenses/LICENSE-2.0
-**
-** Unless required by applicable law or agreed to in writing, software
-** distributed under the License is distributed on an "AS IS" BASIS,
-** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-** See the License for the specific language governing permissions and
-** limitations under the License.
-*/
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
 
 #include <stdint.h>
 
-#ifndef _BOOT_IMAGE_H_
-#define _BOOT_IMAGE_H_
-
 #define BOOT_MAGIC "ANDROID!"
 #define BOOT_MAGIC_SIZE 8
 #define BOOT_NAME_SIZE 16
 #define BOOT_ARGS_SIZE 512
 #define BOOT_EXTRA_ARGS_SIZE 1024
 
-#define BOOT_HEADER_VERSION_ZERO 0
-/*
- *  Bootloader expects the structure of boot_img_hdr with header version
- *  BOOT_HEADER_VERSION_ZERO to be as follows:
- */
+// The bootloader expects the structure of boot_img_hdr with header
+// version 0 to be as follows:
 struct boot_img_hdr_v0 {
+    // Must be BOOT_MAGIC.
     uint8_t magic[BOOT_MAGIC_SIZE];
 
     uint32_t kernel_size; /* size in bytes */
@@ -45,26 +41,36 @@
 
     uint32_t tags_addr; /* physical addr for kernel tags */
     uint32_t page_size; /* flash page size we assume */
-    /*
-     * version for the boot image header.
-     */
+
+    // Version of the boot image header.
     uint32_t header_version;
 
-    /* operating system version and security patch level; for
-     * version "A.B.C" and patch level "Y-M-D":
-     * ver = A << 14 | B << 7 | C         (7 bits for each of A, B, C)
-     * lvl = ((Y - 2000) & 127) << 4 | M  (7 bits for Y, 4 bits for M)
-     * os_version = ver << 11 | lvl */
+    // Operating system version and security patch level.
+    // For version "A.B.C" and patch level "Y-M-D":
+    //   (7 bits for each of A, B, C; 7 bits for (Y-2000), 4 bits for M)
+    //   os_version = A[31:25] B[24:18] C[17:11] (Y-2000)[10:4] M[3:0]
     uint32_t os_version;
 
+#if __cplusplus
+    void SetOsVersion(unsigned major, unsigned minor, unsigned patch) {
+        os_version &= ((1 << 11) - 1);
+        os_version |= (((major & 0x7f) << 25) | ((minor & 0x7f) << 18) | ((patch & 0x7f) << 11));
+    }
+
+    void SetOsPatchLevel(unsigned year, unsigned month) {
+        os_version &= ~((1 << 11) - 1);
+        os_version |= (((year - 2000) & 0x7f) << 4) | ((month & 0xf) << 0);
+    }
+#endif
+
     uint8_t name[BOOT_NAME_SIZE]; /* asciiz product name */
 
     uint8_t cmdline[BOOT_ARGS_SIZE];
 
     uint32_t id[8]; /* timestamp / checksum / sha1 / etc */
 
-    /* Supplemental command line data; kept here to maintain
-     * binary compatibility with older versions of mkbootimg */
+    // Supplemental command line data; kept here to maintain
+    // binary compatibility with older versions of mkbootimg.
     uint8_t extra_cmdline[BOOT_EXTRA_ARGS_SIZE];
 } __attribute__((packed));
 
@@ -74,7 +80,7 @@
  */
 typedef struct boot_img_hdr_v0 boot_img_hdr;
 
-/* When a boot header is of version BOOT_HEADER_VERSION_ZERO, the structure of boot image is as
+/* When a boot header is of version 0, the structure of boot image is as
  * follows:
  *
  * +-----------------+
@@ -103,15 +109,13 @@
  *    else: jump to kernel_addr
  */
 
-#define BOOT_HEADER_VERSION_ONE 1
-
 struct boot_img_hdr_v1 : public boot_img_hdr_v0 {
     uint32_t recovery_dtbo_size;   /* size in bytes for recovery DTBO image */
     uint64_t recovery_dtbo_offset; /* physical load addr */
     uint32_t header_size;
 } __attribute__((packed));
 
-/* When the boot image header has a version of BOOT_HEADER_VERSION_ONE, the structure of the boot
+/* When the boot image header has a version of 1, the structure of the boot
  * image is as follows:
  *
  * +-----------------+
@@ -142,23 +146,3 @@
  * 7. if second_size != 0: jump to second_addr
  *    else: jump to kernel_addr
  */
-
-#if 0
-typedef struct ptentry ptentry;
-
-struct ptentry {
-    char name[16];      /* asciiz partition name    */
-    unsigned start;     /* starting block number    */
-    unsigned length;    /* length in blocks         */
-    unsigned flags;     /* set to zero              */
-};
-
-/* MSM Partition Table ATAG
-**
-** length: 2 + 7 * n
-** atag:   0x4d534d70
-**         <ptentry> x n
-*/
-#endif
-
-#endif