On Mon, Dec 17, 2012 at 2:02 AM, Ritesh Harjani <ritesh.harjani@xxxxxxxxx> wrote:
Hi Yann,On Mon, Dec 17, 2012 at 3:12 PM, Yann Droneaud <ydroneaud@xxxxxxxxxx> wrote:
Le lundi 17 décembre 2012 à 12:41 +0530, Ritesh Harjani a écrit :
> Hi Everyone,The kernel alone is not responsible of interpreting Hayes commands (AT).
>
> When this command (at+cfun=1,1) is executed on phone, it does a
> reboot. I want to know which and how this command calls the kernel
> level functions.
> I googled this, but seems like all the data explains only about AT
> command and not as to how this reboot process is done.
>
According to ETSI TS 100 916 V7.4.0 (1999-11) Technical Specification
Digital cellular telecommunications system (Phase 2+); AT command set
for GSM Mobile Equipment (ME) (GSM 07.07 version 7.4.0 Release 1998),
Section 8.2 Set phone functionality +CFUN (found through by
http://wiki.openmoko.org/wiki/Hardware:AT_Commands ), this command
(AT+CFUN=1,1) is one of the command a "baseband" must implement.
>And this command is asking for a reboot. So what you describe seems more
>likely to be a hardware problem.
On Android phones(some of them) there are essentially two processors. The Application Processor (AP) where your Android operating system (AOS) and user interface (UI) lives, and the Baseband/Cellular Processor (BP/CP) where all the GSM and other high-tech communication magic happens, including the modem we wish to communicate with.
Here, AP and BP communicates via UART (serial line), USB, SPI or through shared RAM and/or a combination of these. Therefore there will always be some path directly accessible from the outside that we should be able to use to communicate directly with the BP.
So, what I am asking for is not any hardware problem. What I have figured out that, this command (at+cun=1,1) calls for sysrq reset which does a emergency restart.
But, I wanted to know the exact path that it follows before calling Sysrq key.
Did you try 'strace'?
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