Re: Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Cédric Le Goater]

Hello Abhishek,

On 3/18/23 18:55, Abhishek Singh Dagur wrote:
> Hi Alex , Cédric,
> we have tried this *option:-serial *pty* -serial *pty* -serial *pty *-serial 
> *pty *-serial *pty to check the serial output on screen.
>
> Here we are providing 2 scenarios without and with the changes suggested by @Cédric 
> Le Goater <mailto:clg@kaod.org> .
> In first we are able to get /dev/ttyS4 serial port not /dev/ttyS2
> In second we are able to get /dev/ttyS2 not /dev/ttyS4
>
> *Scenario1:****previously with normal qemu build i have tried emulation as:*
>
> qemu-system-arm -m 512 -M 
> ast2500-evb,fmc-model=mx66u51235f,spi-model=mx66u51235f -nographic -drive 
> file=./pru-1.2.4_dev-rc1.static.mtd,format=raw,if=mtd -serial pty -serial pty 
> -serial pty -serial pty
>
> which gives us output as.
>
> QEMU 7.2.0 monitor - type 'help' for more information
> (qemu) char device redirected to /dev/pts/15 (label serial0)
> char device redirected to /dev/pts/16 (label serial1)
> char device redirected to /dev/pts/17 (label serial2)
> char device redirected to /dev/pts/18 (label serial3)
>
> so we can use *screen *to interact with the ttyS4 serial port like :
> screen /dev/pts/15
> In which we have our boot process and shell prompt .
>
> *Scenario2:* *when I am using the newly build image with the changes *@Cédric Le 
> Goater <mailto:clg@kaod.org>*  provided*
>
> With the below command:
> ./qemu-system-arm -m 512 -M 
> ast2500-evb,uart-default=uart2,fmc-model=mx66u51235f,spi-model=mx66u51235f 
> -nographic -drive file=./pru-1.2.4_dev-rc1.static.mtd,format=raw,if=mtd -serial 
> pty -serial pty -serial pty -serial pty

Since the machine expect /dev/ttyS2 to be the boot console, the SoC device
to attach to the first serial is UART3. This command line should output
the console logs in the same terminal :

  ./qemu-system-arm -m 512 -M 
ast2500-evb,uart-default=uart3,fmc-model=mx66u51235f,spi-model=mx66u51235f -net 
user -nographic -drive file=./pru-1.2.4_dev-rc1.static.mtd,format=raw,if=mtd 
-serial mon:stdio

I have updated the patch in my aspeed-8.0 tree :

  
https://github.com/legoater/qemu/commit/20fe705361dd7ed1d9129747a8a0b643410869e3

Please note that in this last version, the machine option is simply "uart".

Thanks,

C.