[Buildroot] [PATCH] configs/qemu_riscv{32, 64}_virt_defconfig: Remove BR2_TARGET_GENERIC_GETTY_PORT

[Bin Meng]

Hi Yann,

On Mon, Mar 23, 2020 at 12:13 AM Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
>
> Romain, Bin, All,
>
> On 2020-03-22 17:01 +0100, Yann E. MORIN spake thusly:
> > On 2020-03-22 16:52 +0100, Romain Naour spake thusly:
> > > Le 07/03/2020 à 13:20, Bin Meng a écrit :
> > > > Currently BR2_TARGET_GENERIC_GETTY_PORT is set to ttyS0 in both
> > > > qemu_riscv32_virt and qemu_riscv64_virt defconfig files. This
> > > > limits usecases when the same one rootfs could be used on QEMU
> > > > 'sifive_u' machine and SiFive HiFive Unleashed board.
> > > >
> > > > Remove it so that the default boot console can be used.
> > >
> > > By doing this change, we need to check if -nographic is used to start qemu (so
> > > the serial port is the default console) or if console=ttyS0 is used in the
> > > kernel command line.
> > >
> > > riscv32 and risc64 are both using -nographic to start Qemu.
> > >
> > > Your use case is similar to the one from [1]
> > >
> > > [1]
> > > https://git.buildroot.net/buildroot/commit/?id=131300e6f1d0745a1455d246684550e6ecb68549
> > >
> > > Reviewed-by: Romain Naour <romain.naour at gmail.com>
> >
> > Thanks Romain for this review (and for bringing me in!)
> >
> > However, I disagree: these defconfig files are for qemu, not the real
> > hardware.
> >

I understand your points.

> > Additionally, we do have a configuration for the hifive unleashed board
> > already, hifive_unleashed_defconfig, which is what should be used for
> > the real hardware.
>
> Romain pointed out on IRC that this change is in fact dual-sided:
>
>   - it allows the generic riscv defconfigs to boot on the real hardware
>     HiFive Unleashed board

The changes wanted to make the rootfs be generic so that it can be
reusable among all RISC-V targets. IMO QEMU RISC-V config is the best
candidate to do such things.

>
>   - it allows the generic riscv defconfigs to boot on the emulated
>     HiFive Unleashed board which is known to qemu as sifive_u.
>

That's correct.

> Still, my position does not change: if one wants to boot something in
> the sifive_u which emulates a HiFive Unleashed board, then one better
> use the original hifive_unleashed_defconfig, rather than the generic
> riscv one.
>

The hifive_unleashed_defconfig can do something specific to one
particular board (eg: generating a workable flash or SD card image),
but the proposed change in this patch is for generic RISC-V boards'
rootfs.

Regards,
Bin