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diff --git a/doc/README.android-fastboot-protocol b/doc/README.android-fastboot-protocol new file mode 100644 index 000000000..e9e7166a2 --- /dev/null +++ b/doc/README.android-fastboot-protocol @@ -0,0 +1,170 @@ +FastBoot Version 0.4 +---------------------- + +The fastboot protocol is a mechanism for communicating with bootloaders +over USB. It is designed to be very straightforward to implement, to +allow it to be used across a wide range of devices and from hosts running +Linux, Windows, or OSX. + + +Basic Requirements +------------------ + +* Two bulk endpoints (in, out) are required +* Max packet size must be 64 bytes for full-speed and 512 bytes for + high-speed USB +* The protocol is entirely host-driven and synchronous (unlike the + multi-channel, bi-directional, asynchronous ADB protocol) + + +Transport and Framing +--------------------- + +1. Host sends a command, which is an ascii string in a single + packet no greater than 64 bytes. + +2. Client response with a single packet no greater than 64 bytes. + The first four bytes of the response are "OKAY", "FAIL", "DATA", + or "INFO". Additional bytes may contain an (ascii) informative + message. + + a. INFO -> the remaining 60 bytes are an informative message + (providing progress or diagnostic messages). They should + be displayed and then step #2 repeats + + b. FAIL -> the requested command failed. The remaining 60 bytes + of the response (if present) provide a textual failure message + to present to the user. Stop. + + c. OKAY -> the requested command completed successfully. Go to #5 + + d. DATA -> the requested command is ready for the data phase. + A DATA response packet will be 12 bytes long, in the form of + DATA00000000 where the 8 digit hexidecimal number represents + the total data size to transfer. + +3. Data phase. Depending on the command, the host or client will + send the indicated amount of data. Short packets are always + acceptable and zero-length packets are ignored. This phase continues + until the client has sent or received the number of bytes indicated + in the "DATA" response above. + +4. Client responds with a single packet no greater than 64 bytes. + The first four bytes of the response are "OKAY", "FAIL", or "INFO". + Similar to #2: + + a. INFO -> display the remaining 60 bytes and return to #4 + + b. FAIL -> display the remaining 60 bytes (if present) as a failure + reason and consider the command failed. Stop. + + c. OKAY -> success. Go to #5 + +5. Success. Stop. + + +Example Session +--------------- + +Host: "getvar:version" request version variable + +Client: "OKAY0.4" return version "0.4" + +Host: "getvar:nonexistant" request some undefined variable + +Client: "OKAY" return value "" + +Host: "download:00001234" request to send 0x1234 bytes of data + +Client: "DATA00001234" ready to accept data + +Host: < 0x1234 bytes > send data + +Client: "OKAY" success + +Host: "flash:bootloader" request to flash the data to the bootloader + +Client: "INFOerasing flash" indicate status / progress + "INFOwriting flash" + "OKAY" indicate success + +Host: "powerdown" send a command + +Client: "FAILunknown command" indicate failure + + +Command Reference +----------------- + +* Command parameters are indicated by printf-style escape sequences. + +* Commands are ascii strings and sent without the quotes (which are + for illustration only here) and without a trailing 0 byte. + +* Commands that begin with a lowercase letter are reserved for this + specification. OEM-specific commands should not begin with a + lowercase letter, to prevent incompatibilities with future specs. + + "getvar:%s" Read a config/version variable from the bootloader. + The variable contents will be returned after the + OKAY response. + + "download:%08x" Write data to memory which will be later used + by "boot", "ramdisk", "flash", etc. The client + will reply with "DATA%08x" if it has enough + space in RAM or "FAIL" if not. The size of + the download is remembered. + + "verify:%08x" Send a digital signature to verify the downloaded + data. Required if the bootloader is "secure" + otherwise "flash" and "boot" will be ignored. + + "flash:%s" Write the previously downloaded image to the + named partition (if possible). + + "erase:%s" Erase the indicated partition (clear to 0xFFs) + + "boot" The previously downloaded data is a boot.img + and should be booted according to the normal + procedure for a boot.img + + "continue" Continue booting as normal (if possible) + + "reboot" Reboot the device. + + "reboot-bootloader" Reboot back into the bootloader. + Useful for upgrade processes that require upgrading + the bootloader and then upgrading other partitions + using the new bootloader. + + "powerdown" Power off the device. + + + +Client Variables +---------------- + +The "getvar:%s" command is used to read client variables which +represent various information about the device and the software +on it. + +The various currently defined names are: + + version Version of FastBoot protocol supported. + It should be "0.3" for this document. + + version-bootloader Version string for the Bootloader. + + version-baseband Version string of the Baseband Software + + product Name of the product + + serialno Product serial number + + secure If the value is "yes", this is a secure + bootloader requiring a signature before + it will install or boot images. + +Names starting with a lowercase character are reserved by this +specification. OEM-specific names should not start with lowercase +characters. |