On Mon, Dec 17, 2012 at 2:02 AM, Ritesh Harjani <[email protected]>wrote:
> Hi Yann, > > > On Mon, Dec 17, 2012 at 3:12 PM, Yann Droneaud <[email protected]>wrote: > >> Le lundi 17 décembre 2012 à 12:41 +0530, Ritesh Harjani a écrit : >> > Hi Everyone, >> > >> > 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. >> > >> >> The kernel alone is not responsible of interpreting Hayes commands (AT). >> >> 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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