[Buildroot] Need help with "CONFIG_CMDLINE" or setting up serial console.

[Buildroot] Need help with "CONFIG_CMDLINE" or setting up serial console.

[Aseem Sharma]

Hello,

I have created rootfs and zImage for "arm926t" using the long term support
release of buildroot. However I am having trouble knowing if it is working
as I do not see any messages on the screen.

How do I setup serial console on my device? I am not able to find the usual
"CONFIG_CMDLINE" option in menuconfig to be able to set kernel command line.

It will be really helpful if you can help me with the procedure/workaround
to be able to give command line parameter to the kernel. Or any other means
to redirect the output to ttyS0.

Thanks & Regards,
Aseem
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[Buildroot] Need help with "CONFIG_CMDLINE" or setting up serial console.

[Thomas Petazzoni]

Hello,

On Thu, 24 Aug 2017 07:13:55 +0530, Aseem Sharma wrote:

> I have created rootfs and zImage for "arm926t" using the long term support
> release of buildroot. However I am having trouble knowing if it is working
> as I do not see any messages on the screen.
> 
> How do I setup serial console on my device? I am not able to find the usual
> "CONFIG_CMDLINE" option in menuconfig to be able to set kernel command line.

CONFIG_CMDLINE is a Linux kernel option, not a Buildroot option.

In Buildroot, "make menuconfig" shows you the Buildroot options (which
architecture to use, which packages to build, which filesystem image to
generate, which kernel version and configuration to use, etc.)

If you want to access the Linux kernel configuration in the context of
Buildroot, you need to do "make linux-menuconfig". This is all
explained in the Buildroot manual, so please have a look at it.

However, using CONFIG_CMDLINE is by far not the easiest way of changing
the kernel command line. Instead, if you're using a decent bootloader,
it for sure provides a way to specify the kernel command line. Under
U-Boot for example, the bootargs variable is used for the kernel
command line value.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] Need help with "CONFIG_CMDLINE" or setting up serial console.

[Aseem Sharma]

Thanks Thomas for your inputs and time.

Best Regards,
Aseem

On Thu, Aug 24, 2017 at 10:54 PM, Thomas Petazzoni <
thomas.petazzoni@free-electrons.com> wrote:

> Hello,
>
> On Thu, 24 Aug 2017 07:13:55 +0530, Aseem Sharma wrote:
>
> > I have created rootfs and zImage for "arm926t" using the long term
> support
> > release of buildroot. However I am having trouble knowing if it is
> working
> > as I do not see any messages on the screen.
> >
> > How do I setup serial console on my device? I am not able to find the
> usual
> > "CONFIG_CMDLINE" option in menuconfig to be able to set kernel command
> line.
>
> CONFIG_CMDLINE is a Linux kernel option, not a Buildroot option.
>
> In Buildroot, "make menuconfig" shows you the Buildroot options (which
> architecture to use, which packages to build, which filesystem image to
> generate, which kernel version and configuration to use, etc.)
>
> If you want to access the Linux kernel configuration in the context of
> Buildroot, you need to do "make linux-menuconfig". This is all
> explained in the Buildroot manual, so please have a look at it.
>
> However, using CONFIG_CMDLINE is by far not the easiest way of changing
> the kernel command line. Instead, if you're using a decent bootloader,
> it for sure provides a way to specify the kernel command line. Under
> U-Boot for example, the bootargs variable is used for the kernel
> command line value.
>
> Best regards,
>
> Thomas
> --
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
>
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