diff --git a/bootloader.c b/bootloader.c
index 38b5651..bc79bee 100644
--- a/bootloader.c
+++ b/bootloader.c
@@ -119,3 +119,153 @@ int set_bootloader_message(const struct bootloader_message *in) {
     LOGI("Set boot command \"%s\"\n", in->command[0] != 255 ? in->command : "");
     return 0;
 }
+
+/* Update Image
+ *
+ * - will be stored in the "cache" partition
+ * - bad blocks will be ignored, like boot.img and recovery.img
+ * - the first block will be the image header (described below)
+ * - the size is in BYTES, inclusive of the header
+ * - offsets are in BYTES from the start of the update header
+ * - two raw bitmaps will be included, the "busy" and "fail" bitmaps
+ * - for dream, the bitmaps will be 320x480x16bpp RGB565
+ */
+
+#define UPDATE_MAGIC       "MSM-RADIO-UPDATE"
+#define UPDATE_MAGIC_SIZE  16
+#define UPDATE_VERSION     0x00010000
+
+struct update_header {
+    unsigned char MAGIC[UPDATE_MAGIC_SIZE];
+
+    unsigned version;
+    unsigned size;
+
+    unsigned image_offset;
+    unsigned image_length;
+
+    unsigned bitmap_width;
+    unsigned bitmap_height;
+    unsigned bitmap_bpp;
+
+    unsigned busy_bitmap_offset;
+    unsigned busy_bitmap_length;
+
+    unsigned fail_bitmap_offset;
+    unsigned fail_bitmap_length;
+};
+
+int write_update_for_bootloader(
+        const char *update, int update_length,
+        int bitmap_width, int bitmap_height, int bitmap_bpp,
+        const char *busy_bitmap, const char *fail_bitmap) {
+    if (ensure_root_path_unmounted(CACHE_NAME)) {
+        LOGE("Can't unmount %s\n", CACHE_NAME);
+        return -1;
+    }
+
+    const MtdPartition *part = get_root_mtd_partition(CACHE_NAME);
+    if (part == NULL) {
+        LOGE("Can't find %s\n", CACHE_NAME);
+        return -1;
+    }
+
+    MtdWriteContext *write = mtd_write_partition(part);
+    if (write == NULL) {
+        LOGE("Can't open %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        return -1;
+    }
+
+    /* Write an invalid (zero) header first, to disable any previous
+     * update and any other structured contents (like a filesystem),
+     * and as a placeholder for the amount of space required.
+     */
+
+    struct update_header header;
+    memset(&header, 0, sizeof(header));
+    const ssize_t header_size = sizeof(header);
+    if (mtd_write_data(write, (char*) &header, header_size) != header_size) {
+        LOGE("Can't write header to %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+
+    /* Write each section individually block-aligned, so we can write
+     * each block independently without complicated buffering.
+     */
+
+    memcpy(&header.MAGIC, UPDATE_MAGIC, UPDATE_MAGIC_SIZE);
+    header.version = UPDATE_VERSION;
+    header.size = header_size;
+
+    off_t image_start_pos = mtd_erase_blocks(write, 0);
+    header.image_length = update_length;
+    if ((int) header.image_offset == -1 ||
+        mtd_write_data(write, update, update_length) != update_length) {
+        LOGE("Can't write update to %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+    off_t busy_start_pos = mtd_erase_blocks(write, 0);
+    header.image_offset = mtd_find_write_start(write, image_start_pos);
+
+    header.bitmap_width = bitmap_width;
+    header.bitmap_height = bitmap_height;
+    header.bitmap_bpp = bitmap_bpp;
+
+    int bitmap_length = (bitmap_bpp + 7) / 8 * bitmap_width * bitmap_height;
+
+    header.busy_bitmap_length = busy_bitmap != NULL ? bitmap_length : 0;
+    if ((int) header.busy_bitmap_offset == -1 ||
+        mtd_write_data(write, busy_bitmap, bitmap_length) != bitmap_length) {
+        LOGE("Can't write bitmap to %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+    off_t fail_start_pos = mtd_erase_blocks(write, 0);
+    header.busy_bitmap_offset = mtd_find_write_start(write, busy_start_pos);
+
+    header.fail_bitmap_length = fail_bitmap != NULL ? bitmap_length : 0;
+    if ((int) header.fail_bitmap_offset == -1 ||
+        mtd_write_data(write, fail_bitmap, bitmap_length) != bitmap_length) {
+        LOGE("Can't write bitmap to %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+    mtd_erase_blocks(write, 0);
+    header.fail_bitmap_offset = mtd_find_write_start(write, fail_start_pos);
+
+    /* Write the header last, after all the blocks it refers to, so that
+     * when the magic number is installed everything is valid.
+     */
+
+    if (mtd_write_close(write)) {
+        LOGE("Can't finish writing %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        return -1;
+    }
+
+    write = mtd_write_partition(part);
+    if (write == NULL) {
+        LOGE("Can't reopen %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        return -1;
+    }
+
+    if (mtd_write_data(write, (char*) &header, header_size) != header_size) {
+        LOGE("Can't rewrite header to %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+
+    if (mtd_erase_blocks(write, 0) != image_start_pos) {
+        LOGE("Misalignment rewriting %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        mtd_write_close(write);
+        return -1;
+    }
+
+    if (mtd_write_close(write)) {
+        LOGE("Can't finish header of %s\n(%s)\n", CACHE_NAME, strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/bootloader.h b/bootloader.h
index 2e749aa..3d4302f 100644
--- a/bootloader.h
+++ b/bootloader.h
@@ -47,4 +47,13 @@ struct bootloader_message {
 int get_bootloader_message(struct bootloader_message *out);
 int set_bootloader_message(const struct bootloader_message *in);
 
+/* Write an update to the cache partition for update-radio or update-hboot.
+ * Note, this destroys any filesystem on the cache partition!
+ * The expected bitmap format is 240x320, 16bpp (2Bpp), RGB 5:6:5.
+ */
+int write_update_for_bootloader(
+        const char *update, int update_len,
+        int bitmap_width, int bitmap_height, int bitmap_bpp,
+        const char *busy_bitmap, const char *error_bitmap);
+
 #endif
diff --git a/common.h b/common.h
index fd8605a..81d9029 100644
--- a/common.h
+++ b/common.h
@@ -52,10 +52,17 @@ enum {
   BACKGROUND_ICON_NONE,
   BACKGROUND_ICON_INSTALLING,
   BACKGROUND_ICON_ERROR,
+  BACKGROUND_ICON_FIRMWARE_INSTALLING,
+  BACKGROUND_ICON_FIRMWARE_ERROR,
   NUM_BACKGROUND_ICONS
 };
 void ui_set_background(int icon);
 
+// Get a malloc'd copy of the screen image showing (only) the specified icon.
+// Also returns the width, height, and bits per pixel of the returned image.
+// TODO: Use some sort of "struct Bitmap" here instead of all these variables?
+char *ui_copy_image(int icon, int *width, int *height, int *bpp);
+
 // Show a progress bar and define the scope of the next operation:
 //   portion - fraction of the progress bar the next operation will use
 //   seconds - expected time interval (progress bar moves at this minimum rate)
diff --git a/firmware.c b/firmware.c
new file mode 100644
index 0000000..e2e4fe6
--- /dev/null
+++ b/firmware.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+#include "bootloader.h"
+#include "common.h"
+#include "firmware.h"
+#include "roots.h"
+
+#include <errno.h>
+#include <string.h>
+#include <sys/reboot.h>
+
+static const char *update_type = NULL;
+static const char *update_data = NULL;
+static int update_length = 0;
+
+int remember_firmware_update(const char *type, const char *data, int length) {
+    if (update_type != NULL || update_data != NULL) {
+        LOGE("Multiple firmware images\n");
+        return -1;
+    }
+
+    update_type = type;
+    update_data = data;
+    update_length = length;
+    return 0;
+}
+
+// Return true if there is a firmware update pending.
+int firmware_update_pending() {
+  return update_data != NULL && update_length > 0;
+}
+
+/* Bootloader / Recovery Flow
+ *
+ * On every boot, the bootloader will read the bootloader_message
+ * from flash and check the command field.  The bootloader should
+ * deal with the command field not having a 0 terminator correctly
+ * (so as to not crash if the block is invalid or corrupt).
+ *
+ * The bootloader will have to publish the partition that contains
+ * the bootloader_message to the linux kernel so it can update it.
+ *
+ * if command == "boot-recovery" -> boot recovery.img
+ * else if command == "update-radio" -> update radio image (below)
+ * else if command == "update-hboot" -> update hboot image (below)
+ * else -> boot boot.img (normal boot)
+ *
+ * Radio/Hboot Update Flow
+ * 1. the bootloader will attempt to load and validate the header
+ * 2. if the header is invalid, status="invalid-update", goto #8
+ * 3. display the busy image on-screen
+ * 4. if the update image is invalid, status="invalid-radio-image", goto #8
+ * 5. attempt to update the firmware (depending on the command)
+ * 6. if successful, status="okay", goto #8
+ * 7. if failed, and the old image can still boot, status="failed-update"
+ * 8. write the bootloader_message, leaving the recovery field
+ *    unchanged, updating status, and setting command to
+ *    "boot-recovery"
+ * 9. reboot
+ *
+ * The bootloader will not modify or erase the cache partition.
+ * It is recovery's responsibility to clean up the mess afterwards.
+ */
+
+int maybe_install_firmware_update(const char *send_intent) {
+    if (update_data == NULL || update_length == 0) return 0;
+
+    /* We destroy the cache partition to pass the update image to the
+     * bootloader, so all we can really do afterwards is wipe cache and reboot.
+     * Set up this instruction now, in case we're interrupted while writing.
+     */
+
+    struct bootloader_message boot;
+    memset(&boot, 0, sizeof(boot));
+    strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
+    strlcpy(boot.recovery, "recovery\n--wipe_cache\n", sizeof(boot.command));
+    if (send_intent != NULL) {
+        strlcat(boot.recovery, "--send_intent=", sizeof(boot.recovery));
+        strlcat(boot.recovery, send_intent, sizeof(boot.recovery));
+        strlcat(boot.recovery, "\n", sizeof(boot.recovery));
+    }
+    if (set_bootloader_message(&boot)) return -1;
+
+    int width = 0, height = 0, bpp = 0;
+    char *busy_image = ui_copy_image(
+        BACKGROUND_ICON_FIRMWARE_INSTALLING, &width, &height, &bpp);
+    char *fail_image = ui_copy_image(
+        BACKGROUND_ICON_FIRMWARE_ERROR, &width, &height, &bpp);
+
+    ui_print("Writing %s image...\n", update_type);
+    if (write_update_for_bootloader(
+            update_data, update_length,
+            width, height, bpp, busy_image, fail_image)) {
+        LOGE("Can't write %s image\n(%s)\n", update_type, strerror(errno));
+        format_root_device("CACHE:");  // Attempt to clean cache up, at least.
+        return -1;
+    }
+
+    free(busy_image);
+    free(fail_image);
+
+    /* The update image is fully written, so now we can instruct the bootloader
+     * to install it.  (After doing so, it will come back here, and we will
+     * wipe the cache and reboot into the system.)
+     */
+    snprintf(boot.command, sizeof(boot.command), "update-%s", update_type);
+    if (set_bootloader_message(&boot)) {
+        format_root_device("CACHE:");
+        return -1;
+    }
+
+    reboot(RB_AUTOBOOT);
+
+    // Can't reboot?  WTF?
+    LOGE("Can't reboot\n");
+    return -1;
+}
diff --git a/firmware.h b/firmware.h
new file mode 100644
index 0000000..aeb8f97
--- /dev/null
+++ b/firmware.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+#ifndef _RECOVERY_FIRMWARE_H
+#define _RECOVERY_FIRMWARE_H
+
+/* Save a radio or bootloader update image for later installation.
+ * The type should be one of "hboot" or "radio".
+ * Takes ownership of type and data.  Returns nonzero on error.
+ */
+int remember_firmware_update(const char *type, const char *data, int length);
+
+/* Returns true if a firmware update has been saved. */
+int firmware_update_pending();
+
+/* If an update was saved, reboot into the bootloader now to install it.
+ * Returns 0 if no radio image was defined, nonzero on error,
+ * doesn't return at all on success...
+ */
+int maybe_install_firmware_update(const char *send_intent);
+
+#endif
diff --git a/ui.c b/ui.c
index e08c4a4..4f28725 100644
--- a/ui.c
+++ b/ui.c
@@ -359,6 +359,23 @@ void ui_init(void)
     pthread_create(&t, NULL, input_thread, NULL);
 }
 
+char *ui_copy_image(int icon, int *width, int *height, int *bpp) {
+    pthread_mutex_lock(&gUpdateMutex);
+    draw_background_locked(gBackgroundIcon[icon]);
+    *width = gr_fb_width();
+    *height = gr_fb_height();
+    *bpp = sizeof(gr_pixel) * 8;
+    int size = *width * *height * sizeof(gr_pixel);
+    char *ret = malloc(size);
+    if (ret == NULL) {
+        LOGE("Can't allocate %d bytes for image\n", size);
+    } else {
+        memcpy(ret, gr_fb_data(), size);
+    }
+    pthread_mutex_unlock(&gUpdateMutex);
+    return ret;
+}
+
 void ui_set_background(int icon)
 {
     pthread_mutex_lock(&gUpdateMutex);