Differences

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--- doc:appunti:hardware:android_partitions [2020/01/17 07:44] – [sgdisk] niccolo
+++ doc:appunti:hardware:android_partitions [2020/01/17 12:37] – [The Scatter File] niccolo
@@ Line 8: / Line 8: @@
 **eMMC Flash** combines NAND memory with a built-in controller, that handles most of the things you have to take care of when dealing with NAND flash.
+===== The Scatter File =====
+A Scatter File is a .txt file which is used to describe **parts of flash memory** in an Android device which is running on a MediaTek’s MTK chipeset. Usually, such files are needed at the time of flashing firmware using tools like the **SP Flash Tool**.
+Here it is an **excerpt** of a scatter file, showing **where** to **flash** or **readback** the **recovery partition**:
+<file>
+- partition_index: SYS9
+  partition_name: recovery
+  file_name: recovery.img
+  is_download: true
+  type: NORMAL_ROM
+  linear_start_addr: 0x2D80000
+  physical_start_addr: 0x2D80000
+  partition_size: 0x1000000
+  region: EMMC_USER
+  storage: HW_STORAGE_EMMC
+  boundary_check: true
+  is_reserved: false
+  operation_type: UPDATE
+  reserve: 0x00
+</file>
+The most important data is **linear_start_addr** and **physical_start_addr** (which are always the same, or not?) that states the starting point of that partition into the flash memory, and **partition_size** which is obviously its lenght.
+The **SP Flash Tool** program - when performing a //download// (it means a //flashing//) operation - will write the file into the phone starting at the specified address, checking that the file does not exceed the partition size. During a //readback// operation it will read the entire size specified in the scatter file.
 ===== EMMC Regions =====
-**EMMC_BOOT_1** and **EMMC_USER**
+**Embedded Multi-Media Controller** (eMMC) refers to a package consisting of both flash memory and a flash memory controller integrated into a single on-board chip. Device supports several hardware partitions, it is on-board and thus non removable.
+  * **BOOT** - one or more small partitions intended for boot firmware; eMMC 4.3 spec requires 2 boot partitions.
+  * **RPMB** - Replay Protected Memory Block - intended to store secure data (ie DRM content protection keys); eMMC 4.4 spec adds the requirement of an RPMB partition.
+  * **USER** - a large partition intended for general storage; eMMC 4.3 spec requires 1 user partition.
+Into a **scatter file** you can see references to **region** labeled **EMMC_BOOT_1** and **EMMC_USER**, because partition images can live in that different //partitions// or //regions//. NOTICE: the USER partition or region is normally partitioned in turn into other partitions, so - when referring to eMMC partition - it is advisable to use the //region// term, to avoid confusion.
 ===== Inspecting partitions on the command line =====
-The following commands were executed on a **ZTE Blade A610**, running **Android 6.0**, via the **adb shell** command. The phone was rooted so that the **su** command was available.
+The following commands were executed on a **ZTE Blade A610**, running **Android 6.0**, via the **adb shell** command line. The phone was rooted so that the **su** command was available.
 ==== cat /proc/partitions ====
@@ Line 53: / Line 85: @@
 </code>
+The **mmcblk0** partition is actually the eMMC **USER** region, sized 15388672 blocks (15028 Mb). It is in turn partitioned in 23 partitions. The **boot0**, **boot1** and **rpmb** partitions have a size of 4096 blocks each, i.e. **4194304 (0x400000) bytes**.
 ==== sgdisk ====
@@ Line 58: / Line 91: @@
 <code>
-sgdisk --print /dev/block/mmcblk0                                              <
+sgdisk --print /dev/block/mmcblk0
 Disk /dev/block/mmcblk0: 30777344 sectors, 14.7 GiB
 Logical sector size: 512 bytes
@@ Line 92: / Line 125: @@
         30743552        30776319   16.0 MiB    0700  flashinfo
 </code>
+Doing the math, you can see that the 23 partitions existing in **mmcblk0** leave some space: One is at the begin, sized 1024 sectors or **524288 (0x80000) bytes**. The other unpartitioned space is at the end, the size can be calculated by the difference of size shown by ''cat /proc/partitions'', it is again **524288 (0x80000) bytes**. Theese two spaces are referred into the scatter file as **pgpt** and **sgpt** respectively (primary and secondary GPT parition tables?).
+==== /dev/block/mmcblk0boot0 ====
+The partition **/dev/block/mmcblk0boot0** is the one referred as region **EMMC_BOOT_1** in the scatter file, and it is dedicated to the **preloader**.
+The actual Linux device content starts with the characters **EMMC_BOOT**. It seems that it is an header of **2048 (0x800) bytes** and the actual preloader follows that header. FIXME Some stock ROMs include the preloader image, without that header. But if you readback the preloader partition using **SP Flash Tool**, you get an image with that heder included.
 ===== Web References =====
-  * **[[http://www.lieberbiber.de/2015/07/02/mediatek-details-soc-startup/]]**
+  * **[[http://www.lieberbiber.de/2015/07/02/mediatek-details-soc-startup/|MediaTek details: SoC startup]]**
   * **[[http://www.lieberbiber.de/2015/07/04/mediatek-details-partitions-and-preloader/|MediaTek details: Partitions and Preloader]]**
+  * **[[http://trac.gateworks.com/wiki/MMC|MultiMediaCard (MMC)]]**