Initial Contribution

6 files changed, 970 insertions, 0 deletions

diff --git a/mtdutils/Android.mk b/mtdutils/Android.mk
new file mode 100644
index 0000000..c75eb01
--- /dev/null
+++ b/mtdutils/Android.mk
@@ -0,0 +1,21 @@
+ifneq ($(TARGET_SIMULATOR),true)
+
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+LOCAL_SRC_FILES := \
+	mtdutils.c \
+	mounts.c
+
+LOCAL_MODULE := libmtdutils
+
+include $(BUILD_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES := flash_image.c
+LOCAL_MODULE := flash_image
+LOCAL_STATIC_LIBRARIES := libmtdutils
+LOCAL_SHARED_LIBRARIES := libcutils libc
+include $(BUILD_EXECUTABLE)
+
+endif	# !TARGET_SIMULATOR
diff --git a/mtdutils/flash_image.c b/mtdutils/flash_image.c
new file mode 100644
index 0000000..c776876
--- /dev/null
+++ b/mtdutils/flash_image.c
@@ -0,0 +1,140 @@
+/*
+ * 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 <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "cutils/log.h"
+#include "mtdutils.h"
+
+#define LOG_TAG "flash_image"
+
+#define HEADER_SIZE 2048  // size of header to compare for equality
+
+void die(const char *msg, ...) {
+    int err = errno;
+    va_list args;
+    va_start(args, msg);
+    char buf[1024];
+    vsnprintf(buf, sizeof(buf), msg, args);
+    va_end(args);
+
+    if (err != 0) {
+        strlcat(buf, ": ", sizeof(buf));
+        strlcat(buf, strerror(err), sizeof(buf));
+    }
+
+    fprintf(stderr, "%s\n", buf);
+    LOGE("%s\n", buf);
+    exit(1);
+}
+
+/* Read an image file and write it to a flash partition. */
+
+int main(int argc, char **argv) {
+    const MtdPartition *ptn;
+    MtdWriteContext *write;
+    void *data;
+    unsigned sz;
+
+    if (argc != 3) {
+        fprintf(stderr, "usage: %s partition file.img\n", argv[0]);
+        return 2;
+    }
+
+    if (mtd_scan_partitions() <= 0) die("error scanning partitions");
+    const MtdPartition *partition = mtd_find_partition_by_name(argv[1]);
+    if (partition == NULL) die("can't find %s partition", argv[1]);
+
+    // If the first part of the file matches the partition, skip writing
+
+    int fd = open(argv[2], O_RDONLY);
+    if (fd < 0) die("error opening %s", argv[2]);
+
+    char header[HEADER_SIZE];
+    int headerlen = read(fd, header, sizeof(header));
+    if (headerlen <= 0) die("error reading %s header", argv[2]);
+
+    MtdReadContext *in = mtd_read_partition(partition);
+    if (in == NULL) {
+        LOGW("error opening %s: %s\n", argv[1], strerror(errno));
+        // just assume it needs re-writing
+    } else {
+        char check[HEADER_SIZE];
+        int checklen = mtd_read_data(in, check, sizeof(check));
+        if (checklen <= 0) {
+            LOGW("error reading %s: %s\n", argv[1], strerror(errno));
+            // just assume it needs re-writing
+        } else if (checklen == headerlen && !memcmp(header, check, headerlen)) {
+            LOGI("header is the same, not flashing %s\n", argv[1]);
+            return 0;
+        }
+        mtd_read_close(in);
+    }
+
+    // Skip the header (we'll come back to it), write everything else
+    LOGI("flashing %s from %s\n", argv[1], argv[2]);
+
+    MtdWriteContext *out = mtd_write_partition(partition);
+    if (out == NULL) die("error writing %s", argv[1]);
+
+    char buf[HEADER_SIZE];
+    memset(buf, 0, headerlen);
+    int wrote = mtd_write_data(out, buf, headerlen);
+    if (wrote != headerlen) die("error writing %s", argv[1]);
+
+    int len;
+    while ((len = read(fd, buf, sizeof(buf))) > 0) {
+        wrote = mtd_write_data(out, buf, len);
+        if (wrote != len) die("error writing %s", argv[1]);
+    }
+    if (len < 0) die("error reading %s", argv[2]);
+
+    if (mtd_write_close(out)) die("error closing %s", argv[1]);
+
+    // Now come back and write the header last
+
+    out = mtd_write_partition(partition);
+    if (out == NULL) die("error re-opening %s", argv[1]);
+
+    wrote = mtd_write_data(out, header, headerlen);
+    if (wrote != headerlen) die("error re-writing %s", argv[1]);
+
+    // Need to write a complete block, so write the rest of the first block
+    size_t block_size;
+    if (mtd_partition_info(partition, NULL, &block_size, NULL))
+        die("error getting %s block size", argv[1]);
+
+    if (lseek(fd, headerlen, SEEK_SET) != headerlen)
+        die("error rewinding %s", argv[2]);
+
+    int left = block_size - headerlen;
+    while (left < 0) left += block_size;
+    while (left > 0) {
+        len = read(fd, buf, left > (int)sizeof(buf) ? (int)sizeof(buf) : left);
+        if (len <= 0) die("error reading %s", argv[2]);
+        if (mtd_write_data(out, buf, len) != len)
+            die("error writing %s", argv[1]);
+        left -= len;
+    }
+
+    if (mtd_write_close(out)) die("error closing %s", argv[1]);
+    return 0;
+}
diff --git a/mtdutils/mounts.c b/mtdutils/mounts.c
new file mode 100644
index 0000000..2ab3ff6
--- /dev/null
+++ b/mtdutils/mounts.c
@@ -0,0 +1,214 @@
+/*
+ * 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.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/mount.h>
+
+#include "mounts.h"
+
+struct MountedVolume {
+    const char *device;
+    const char *mount_point;
+    const char *filesystem;
+    const char *flags;
+};
+
+typedef struct {
+    MountedVolume *volumes;
+    int volumes_allocd;
+    int volume_count;
+} MountsState;
+
+static MountsState g_mounts_state = {
+    NULL,   // volumes
+    0,      // volumes_allocd
+    0       // volume_count
+};
+
+static inline void
+free_volume_internals(const MountedVolume *volume, int zero)
+{
+    free((char *)volume->device);
+    free((char *)volume->mount_point);
+    free((char *)volume->filesystem);
+    free((char *)volume->flags);
+    if (zero) {
+        memset((void *)volume, 0, sizeof(*volume));
+    }
+}
+
+#define PROC_MOUNTS_FILENAME   "/proc/mounts"
+
+int
+scan_mounted_volumes()
+{
+    char buf[2048];
+    const char *bufp;
+    int fd;
+    ssize_t nbytes;
+
+    if (g_mounts_state.volumes == NULL) {
+        const int numv = 32;
+        MountedVolume *volumes = malloc(numv * sizeof(*volumes));
+        if (volumes == NULL) {
+            errno = ENOMEM;
+            return -1;
+        }
+        g_mounts_state.volumes = volumes;
+        g_mounts_state.volumes_allocd = numv;
+        memset(volumes, 0, numv * sizeof(*volumes));
+    } else {
+        /* Free the old volume strings.
+         */
+        int i;
+        for (i = 0; i < g_mounts_state.volume_count; i++) {
+            free_volume_internals(&g_mounts_state.volumes[i], 1);
+        }
+    }
+    g_mounts_state.volume_count = 0;
+
+    /* Open and read the file contents.
+     */
+    fd = open(PROC_MOUNTS_FILENAME, O_RDONLY);
+    if (fd < 0) {
+        goto bail;
+    }
+    nbytes = read(fd, buf, sizeof(buf) - 1);
+    close(fd);
+    if (nbytes < 0) {
+        goto bail;
+    }
+    buf[nbytes] = '\0';
+
+    /* Parse the contents of the file, which looks like:
+     *
+     *     # cat /proc/mounts
+     *     rootfs / rootfs rw 0 0
+     *     /dev/pts /dev/pts devpts rw 0 0
+     *     /proc /proc proc rw 0 0
+     *     /sys /sys sysfs rw 0 0
+     *     /dev/block/mtdblock4 /system yaffs2 rw,nodev,noatime,nodiratime 0 0
+     *     /dev/block/mtdblock5 /data yaffs2 rw,nodev,noatime,nodiratime 0 0
+     *     /dev/block/mmcblk0p1 /sdcard vfat rw,sync,dirsync,fmask=0000,dmask=0000,codepage=cp437,iocharset=iso8859-1,utf8 0 0
+     *
+     * The zeroes at the end are dummy placeholder fields to make the
+     * output match Linux's /etc/mtab, but don't represent anything here.
+     */
+    bufp = buf;
+    while (nbytes > 0) {
+        char device[64];
+        char mount_point[64];
+        char filesystem[64];
+        char flags[128];
+        int matches;
+
+        /* %as is a gnu extension that malloc()s a string for each field.
+         */
+        matches = sscanf(bufp, "%63s %63s %63s %127s",
+                device, mount_point, filesystem, flags);
+
+        if (matches == 4) {
+            device[sizeof(device)-1] = '\0';
+            mount_point[sizeof(mount_point)-1] = '\0';
+            filesystem[sizeof(filesystem)-1] = '\0';
+            flags[sizeof(flags)-1] = '\0';
+
+            MountedVolume *v =
+                    &g_mounts_state.volumes[g_mounts_state.volume_count++];
+            v->device = strdup(device);
+            v->mount_point = strdup(mount_point);
+            v->filesystem = strdup(filesystem);
+            v->flags = strdup(flags);
+        } else {
+printf("matches was %d on <<%.40s>>\n", matches, bufp);
+        }
+
+        /* Eat the line.
+         */
+        while (nbytes > 0 && *bufp != '\n') {
+            bufp++;
+            nbytes--;
+        }
+        if (nbytes > 0) {
+            bufp++;
+            nbytes--;
+        }
+    }
+
+    return 0;
+
+bail:
+//TODO: free the strings we've allocated.
+    g_mounts_state.volume_count = 0;
+    return -1;
+}
+
+const MountedVolume *
+find_mounted_volume_by_device(const char *device)
+{
+    if (g_mounts_state.volumes != NULL) {
+        int i;
+        for (i = 0; i < g_mounts_state.volume_count; i++) {
+            MountedVolume *v = &g_mounts_state.volumes[i];
+            /* May be null if it was unmounted and we haven't rescanned.
+             */
+            if (v->device != NULL) {
+                if (strcmp(v->device, device) == 0) {
+                    return v;
+                }
+            }
+        }
+    }
+    return NULL;
+}
+
+const MountedVolume *
+find_mounted_volume_by_mount_point(const char *mount_point)
+{
+    if (g_mounts_state.volumes != NULL) {
+        int i;
+        for (i = 0; i < g_mounts_state.volume_count; i++) {
+            MountedVolume *v = &g_mounts_state.volumes[i];
+            /* May be null if it was unmounted and we haven't rescanned.
+             */
+            if (v->mount_point != NULL) {
+                if (strcmp(v->mount_point, mount_point) == 0) {
+                    return v;
+                }
+            }
+        }
+    }
+    return NULL;
+}
+
+int
+unmount_mounted_volume(const MountedVolume *volume)
+{
+    /* Intentionally pass NULL to umount if the caller tries
+     * to unmount a volume they already unmounted using this
+     * function.
+     */
+    int ret = umount(volume->mount_point);
+    if (ret == 0) {
+        free_volume_internals(volume, 1);
+        return 0;
+    }
+    return ret;
+}
diff --git a/mtdutils/mounts.h b/mtdutils/mounts.h
new file mode 100644
index 0000000..2e2765a
--- /dev/null
+++ b/mtdutils/mounts.h
@@ -0,0 +1,31 @@
+/*
+ * 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.
+ */
+
+#ifndef MTDUTILS_MOUNTS_H_
+#define MTDUTILS_MOUNTS_H_
+
+typedef struct MountedVolume MountedVolume;
+
+int scan_mounted_volumes(void);
+
+const MountedVolume *find_mounted_volume_by_device(const char *device);
+
+const MountedVolume *
+find_mounted_volume_by_mount_point(const char *mount_point);
+
+int unmount_mounted_volume(const MountedVolume *volume);
+
+#endif  // MTDUTILS_MOUNTS_H_
diff --git a/mtdutils/mtdutils.c b/mtdutils/mtdutils.c
new file mode 100644
index 0000000..2b0106f
--- /dev/null
+++ b/mtdutils/mtdutils.c
@@ -0,0 +1,510 @@
+/*
+ * 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.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/mount.h>  // for _IOW, _IOR, mount()
+#include <sys/stat.h>
+#include <mtd/mtd-user.h>
+#undef NDEBUG
+#include <assert.h>
+
+#include "mtdutils.h"
+
+struct MtdPartition {
+    int device_index;
+    unsigned int size;
+    unsigned int erase_size;
+    char *name;
+};
+
+struct MtdReadContext {
+    const MtdPartition *partition;
+    char *buffer;
+    size_t consumed;
+    int fd;
+};
+
+struct MtdWriteContext {
+    const MtdPartition *partition;
+    char *buffer;
+    size_t stored;
+    int fd;
+};
+
+typedef struct {
+    MtdPartition *partitions;
+    int partitions_allocd;
+    int partition_count;
+} MtdState;
+
+static MtdState g_mtd_state = {
+    NULL,   // partitions
+    0,      // partitions_allocd
+    -1      // partition_count
+};
+
+#define MTD_PROC_FILENAME   "/proc/mtd"
+
+int
+mtd_scan_partitions()
+{
+    char buf[2048];
+    const char *bufp;
+    int fd;
+    int i;
+    ssize_t nbytes;
+
+    if (g_mtd_state.partitions == NULL) {
+        const int nump = 32;
+        MtdPartition *partitions = malloc(nump * sizeof(*partitions));
+        if (partitions == NULL) {
+            errno = ENOMEM;
+            return -1;
+        }
+        g_mtd_state.partitions = partitions;
+        g_mtd_state.partitions_allocd = nump;
+        memset(partitions, 0, nump * sizeof(*partitions));
+    }
+    g_mtd_state.partition_count = 0;
+
+    /* Initialize all of the entries to make things easier later.
+     * (Lets us handle sparsely-numbered partitions, which
+     * may not even be possible.)
+     */
+    for (i = 0; i < g_mtd_state.partitions_allocd; i++) {
+        MtdPartition *p = &g_mtd_state.partitions[i];
+        if (p->name != NULL) {
+            free(p->name);
+            p->name = NULL;
+        }
+        p->device_index = -1;
+    }
+
+    /* Open and read the file contents.
+     */
+    fd = open(MTD_PROC_FILENAME, O_RDONLY);
+    if (fd < 0) {
+        goto bail;
+    }
+    nbytes = read(fd, buf, sizeof(buf) - 1);
+    close(fd);
+    if (nbytes < 0) {
+        goto bail;
+    }
+    buf[nbytes] = '\0';
+
+    /* Parse the contents of the file, which looks like:
+     *
+     *     # cat /proc/mtd
+     *     dev:    size   erasesize  name
+     *     mtd0: 00080000 00020000 "bootloader"
+     *     mtd1: 00400000 00020000 "mfg_and_gsm"
+     *     mtd2: 00400000 00020000 "0000000c"
+     *     mtd3: 00200000 00020000 "0000000d"
+     *     mtd4: 04000000 00020000 "system"
+     *     mtd5: 03280000 00020000 "userdata"
+     */
+    bufp = buf;
+    while (nbytes > 0) {
+        int mtdnum, mtdsize, mtderasesize;
+        int matches;
+        char mtdname[64];
+        mtdname[0] = '\0';
+        mtdnum = -1;
+
+        matches = sscanf(bufp, "mtd%d: %x %x \"%63[^\"]",
+                &mtdnum, &mtdsize, &mtderasesize, mtdname);
+        /* This will fail on the first line, which just contains
+         * column headers.
+         */
+        if (matches == 4) {
+            MtdPartition *p = &g_mtd_state.partitions[mtdnum];
+            p->device_index = mtdnum;
+            p->size = mtdsize;
+            p->erase_size = mtderasesize;
+            p->name = strdup(mtdname);
+            if (p->name == NULL) {
+                errno = ENOMEM;
+                goto bail;
+            }
+            g_mtd_state.partition_count++;
+        }
+
+        /* Eat the line.
+         */
+        while (nbytes > 0 && *bufp != '\n') {
+            bufp++;
+            nbytes--;
+        }
+        if (nbytes > 0) {
+            bufp++;
+            nbytes--;
+        }
+    }
+
+    return g_mtd_state.partition_count;
+
+bail:
+    // keep "partitions" around so we can free the names on a rescan.
+    g_mtd_state.partition_count = -1;
+    return -1;
+}
+
+const MtdPartition *
+mtd_find_partition_by_name(const char *name)
+{
+    if (g_mtd_state.partitions != NULL) {
+        int i;
+        for (i = 0; i < g_mtd_state.partitions_allocd; i++) {
+            MtdPartition *p = &g_mtd_state.partitions[i];
+            if (p->device_index >= 0 && p->name != NULL) {
+                if (strcmp(p->name, name) == 0) {
+                    return p;
+                }
+            }
+        }
+    }
+    return NULL;
+}
+
+int
+mtd_mount_partition(const MtdPartition *partition, const char *mount_point,
+        const char *filesystem, int read_only)
+{
+    const unsigned long flags = MS_NOATIME | MS_NODEV | MS_NODIRATIME;
+    char devname[64];
+    int rv = -1;
+
+    sprintf(devname, "/dev/block/mtdblock%d", partition->device_index);
+    if (!read_only) {
+        rv = mount(devname, mount_point, filesystem, flags, NULL);
+    }
+    if (read_only || rv < 0) {
+        rv = mount(devname, mount_point, filesystem, flags | MS_RDONLY, 0);
+        if (rv < 0) {
+            printf("Failed to mount %s on %s: %s\n",
+                    devname, mount_point, strerror(errno));
+        } else {
+            printf("Mount %s on %s read-only\n", devname, mount_point);
+        }
+    }
+#if 1   //TODO: figure out why this is happening; remove include of stat.h
+    if (rv >= 0) {
+        /* For some reason, the x bits sometimes aren't set on the root
+         * of mounted volumes.
+         */
+        struct stat st;
+        rv = stat(mount_point, &st);
+        if (rv < 0) {
+            return rv;
+        }
+        mode_t new_mode = st.st_mode | S_IXUSR | S_IXGRP | S_IXOTH;
+        if (new_mode != st.st_mode) {
+printf("Fixing execute permissions for %s\n", mount_point);
+            rv = chmod(mount_point, new_mode);
+            if (rv < 0) {
+                printf("Couldn't fix permissions for %s: %s\n",
+                        mount_point, strerror(errno));
+            }
+        }
+    }
+#endif
+    return rv;
+}
+
+int
+mtd_partition_info(const MtdPartition *partition,
+        size_t *total_size, size_t *erase_size, size_t *write_size)
+{
+    char mtddevname[32];
+    sprintf(mtddevname, "/dev/mtd/mtd%d", partition->device_index);
+    int fd = open(mtddevname, O_RDONLY);
+    if (fd < 0) return -1;
+
+    struct mtd_info_user mtd_info;
+    int ret = ioctl(fd, MEMGETINFO, &mtd_info);
+    close(fd);
+    if (ret < 0) return -1;
+
+    if (total_size != NULL) *total_size = mtd_info.size;
+    if (erase_size != NULL) *erase_size = mtd_info.erasesize;
+    if (write_size != NULL) *write_size = mtd_info.writesize;
+    return 0;
+}
+
+MtdReadContext *mtd_read_partition(const MtdPartition *partition)
+{
+    MtdReadContext *ctx = (MtdReadContext*) malloc(sizeof(MtdReadContext));
+    if (ctx == NULL) return NULL;
+
+    ctx->buffer = malloc(partition->erase_size);
+    if (ctx->buffer == NULL) {
+        free(ctx);
+        return NULL;
+    }
+
+    char mtddevname[32];
+    sprintf(mtddevname, "/dev/mtd/mtd%d", partition->device_index);
+    ctx->fd = open(mtddevname, O_RDONLY);
+    if (ctx->fd < 0) {
+        free(ctx);
+        free(ctx->buffer);
+        return NULL;
+    }
+
+    ctx->partition = partition;
+    ctx->consumed = partition->erase_size;
+    return ctx;
+}
+
+static int read_block(const MtdPartition *partition, int fd, char *data)
+{
+    struct mtd_ecc_stats before, after;
+    if (ioctl(fd, ECCGETSTATS, &before)) {
+        fprintf(stderr, "mtd: ECCGETSTATS error (%s)\n", strerror(errno));
+        return -1;
+    }
+
+    off_t pos = lseek(fd, 0, SEEK_CUR);
+    ssize_t size = partition->erase_size;
+    while (pos + size <= (int) partition->size) {
+        if (lseek(fd, pos, SEEK_SET) != pos || read(fd, data, size) != size) {
+            fprintf(stderr, "mtd: read error at 0x%08lx (%s)\n",
+                    pos, strerror(errno));
+        } else if (ioctl(fd, ECCGETSTATS, &after)) {
+            fprintf(stderr, "mtd: ECCGETSTATS error (%s)\n", strerror(errno));
+            return -1;
+        } else if (after.failed != before.failed) {
+            fprintf(stderr, "mtd: ECC errors (%d soft, %d hard) at 0x%08lx\n",
+                    after.corrected - before.corrected,
+                    after.failed - before.failed, pos);
+        } else {
+            return 0;  // Success!
+        }
+
+        pos += partition->erase_size;
+    }
+
+    errno = ENOSPC;
+    return -1;
+}
+
+ssize_t mtd_read_data(MtdReadContext *ctx, char *data, size_t len)
+{
+    ssize_t read = 0;
+    while (read < (int) len) {
+        if (ctx->consumed < ctx->partition->erase_size) {
+            size_t avail = ctx->partition->erase_size - ctx->consumed;
+            size_t copy = len - read < avail ? len - read : avail;
+            memcpy(data + read, ctx->buffer + ctx->consumed, copy);
+            ctx->consumed += copy;
+            read += copy;
+        }
+
+        // Read complete blocks directly into the user's buffer
+        while (ctx->consumed == ctx->partition->erase_size &&
+               len - read >= ctx->partition->erase_size) {
+            if (read_block(ctx->partition, ctx->fd, data + read)) return -1;
+            read += ctx->partition->erase_size;
+        }
+
+        // Read the next block into the buffer
+        if (ctx->consumed == ctx->partition->erase_size && read < (int) len) {
+            if (read_block(ctx->partition, ctx->fd, ctx->buffer)) return -1;
+            ctx->consumed = 0;
+        }
+    }
+
+    return read;
+}
+
+void mtd_read_close(MtdReadContext *ctx)
+{
+    close(ctx->fd);
+    free(ctx->buffer);
+    free(ctx);
+}
+
+MtdWriteContext *mtd_write_partition(const MtdPartition *partition)
+{
+    MtdWriteContext *ctx = (MtdWriteContext*) malloc(sizeof(MtdWriteContext));
+    if (ctx == NULL) return NULL;
+
+    ctx->buffer = malloc(partition->erase_size);
+    if (ctx->buffer == NULL) {
+        free(ctx);
+        return NULL;
+    }
+
+    char mtddevname[32];
+    sprintf(mtddevname, "/dev/mtd/mtd%d", partition->device_index);
+    ctx->fd = open(mtddevname, O_RDWR);
+    if (ctx->fd < 0) {
+        free(ctx->buffer);
+        free(ctx);
+        return NULL;
+    }
+
+    ctx->partition = partition;
+    ctx->stored = 0;
+    return ctx;
+}
+
+static int write_block(const MtdPartition *partition, int fd, const char *data)
+{
+    off_t pos = lseek(fd, 0, SEEK_CUR);
+    if (pos == (off_t) -1) return 1;
+
+    ssize_t size = partition->erase_size;
+    while (pos + size <= (int) partition->size) {
+        loff_t bpos = pos;
+        if (ioctl(fd, MEMGETBADBLOCK, &bpos) > 0) {
+            fprintf(stderr, "mtd: not writing bad block at 0x%08lx\n", pos);
+            pos += partition->erase_size;
+            continue;  // Don't try to erase known factory-bad blocks.
+        }
+
+        struct erase_info_user erase_info;
+        erase_info.start = pos;
+        erase_info.length = size;
+        int retry;
+        for (retry = 0; retry < 2; ++retry) {
+            if (ioctl(fd, MEMERASE, &erase_info) < 0) {
+                fprintf(stderr, "mtd: erase failure at 0x%08lx (%s)\n",
+                        pos, strerror(errno));
+                continue;
+            }
+            if (lseek(fd, pos, SEEK_SET) != pos ||
+                write(fd, data, size) != size) {
+                fprintf(stderr, "mtd: write error at 0x%08lx (%s)\n",
+                        pos, strerror(errno));
+            }
+
+            char verify[size];
+            if (lseek(fd, pos, SEEK_SET) != pos ||
+                read(fd, verify, size) != size) {
+                fprintf(stderr, "mtd: re-read error at 0x%08lx (%s)\n",
+                        pos, strerror(errno));
+                continue;
+            }
+            if (memcmp(data, verify, size) != 0) {
+                fprintf(stderr, "mtd: verification error at 0x%08lx (%s)\n",
+                        pos, strerror(errno));
+                continue;
+            }
+
+            if (retry > 0) {
+                fprintf(stderr, "mtd: wrote block after %d retries\n", retry);
+            }
+            return 0;  // Success!
+        }
+
+        // Try to erase it once more as we give up on this block
+        fprintf(stderr, "mtd: skipping write block at 0x%08lx\n", pos);
+        ioctl(fd, MEMERASE, &erase_info);
+        pos += partition->erase_size;
+    }
+
+    // Ran out of space on the device
+    errno = ENOSPC;
+    return -1;
+}
+
+ssize_t mtd_write_data(MtdWriteContext *ctx, const char *data, size_t len)
+{
+    size_t wrote = 0;
+    while (wrote < len) {
+        // Coalesce partial writes into complete blocks
+        if (ctx->stored > 0 || len - wrote < ctx->partition->erase_size) {
+            size_t avail = ctx->partition->erase_size - ctx->stored;
+            size_t copy = len - wrote < avail ? len - wrote : avail;
+            memcpy(ctx->buffer + ctx->stored, data + wrote, copy);
+            ctx->stored += copy;
+            wrote += copy;
+        }
+
+        // If a complete block was accumulated, write it
+        if (ctx->stored == ctx->partition->erase_size) {
+            if (write_block(ctx->partition, ctx->fd, ctx->buffer)) return -1;
+            ctx->stored = 0;
+        }
+
+        // Write complete blocks directly from the user's buffer
+        while (ctx->stored == 0 && len - wrote >= ctx->partition->erase_size) {
+            if (write_block(ctx->partition, ctx->fd, data + wrote)) return -1;
+            wrote += ctx->partition->erase_size;
+        }
+    }
+
+    return wrote;
+}
+
+off_t mtd_erase_blocks(MtdWriteContext *ctx, int blocks)
+{
+    // Zero-pad and write any pending data to get us to a block boundary
+    if (ctx->stored > 0) {
+        size_t zero = ctx->partition->erase_size - ctx->stored;
+        memset(ctx->buffer + ctx->stored, 0, zero);
+        if (write_block(ctx->partition, ctx->fd, ctx->buffer)) return -1;
+        ctx->stored = 0;
+    }
+
+    off_t pos = lseek(ctx->fd, 0, SEEK_CUR);
+    if ((off_t) pos == (off_t) -1) return pos;
+
+    const int total = (ctx->partition->size - pos) / ctx->partition->erase_size;
+    if (blocks < 0) blocks = total;
+    if (blocks > total) {
+        errno = ENOSPC;
+        return -1;
+    }
+
+    // Erase the specified number of blocks
+    while (blocks-- > 0) {
+        loff_t bpos = pos;
+        if (ioctl(ctx->fd, MEMGETBADBLOCK, &bpos) > 0) {
+            fprintf(stderr, "mtd: not erasing bad block at 0x%08lx\n", pos);
+            pos += ctx->partition->erase_size;
+            continue;  // Don't try to erase known factory-bad blocks.
+        }
+
+        struct erase_info_user erase_info;
+        erase_info.start = pos;
+        erase_info.length = ctx->partition->erase_size;
+        if (ioctl(ctx->fd, MEMERASE, &erase_info) < 0) {
+            fprintf(stderr, "mtd: erase failure at 0x%08lx\n", pos);
+        }
+        pos += ctx->partition->erase_size;
+    }
+
+    return pos;
+}
+
+int mtd_write_close(MtdWriteContext *ctx)
+{
+    int r = 0;
+    // Make sure any pending data gets written
+    if (mtd_erase_blocks(ctx, 0) == (off_t) -1) r = -1;
+    if (close(ctx->fd)) r = -1;
+    free(ctx->buffer);
+    free(ctx);
+    return r;
+}
diff --git a/mtdutils/mtdutils.h b/mtdutils/mtdutils.h
new file mode 100644
index 0000000..8d2cb56
--- /dev/null
+++ b/mtdutils/mtdutils.h
@@ -0,0 +1,54 @@
+/*
+ * 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.
+ */
+
+#ifndef MTDUTILS_H_
+#define MTDUTILS_H_
+
+#include <sys/types.h>  // for size_t, etc.
+
+typedef struct MtdPartition MtdPartition;
+
+int mtd_scan_partitions(void);
+
+const MtdPartition *mtd_find_partition_by_name(const char *name);
+
+/* mount_point is like "/system"
+ * filesystem is like "yaffs2"
+ */
+int mtd_mount_partition(const MtdPartition *partition, const char *mount_point,
+        const char *filesystem, int read_only);
+
+/* get the partition and the minimum erase/write block size.  NULL is ok.
+ */
+int mtd_partition_info(const MtdPartition *partition,
+        size_t *total_size, size_t *erase_size, size_t *write_size);
+
+/* read or write raw data from a partition, starting at the beginning.
+ * skips bad blocks as best we can.
+ */
+typedef struct MtdReadContext MtdReadContext;
+typedef struct MtdWriteContext MtdWriteContext;
+
+MtdReadContext *mtd_read_partition(const MtdPartition *);
+ssize_t mtd_read_data(MtdReadContext *, char *data, size_t data_len);
+void mtd_read_close(MtdReadContext *);
+
+MtdWriteContext *mtd_write_partition(const MtdPartition *);
+ssize_t mtd_write_data(MtdWriteContext *, const char *data, size_t data_len);
+off_t mtd_erase_blocks(MtdWriteContext *, int blocks);  /* 0 ok, -1 for all */
+int mtd_write_close(MtdWriteContext *);
+
+#endif  // MTDUTILS_H_