Re: [PATCH] tty: Don't force RISCV SBI console as preferred console

[Paul Walmsley]

On Fri, 26 Apr 2019, Anup Patel wrote:

> On Fri, Apr 26, 2019 at 11:51 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> >
> > On Thu, Apr 25, 2019 at 09:41:21PM -0700, Atish Patra wrote:
> > > Do we even need HVC_SBI console to be enabled by default? Disabling
> > > CONFIG_HVC_RISCV_SBI seems to be fine while running in QEMU.
> > >
> > > If we don't need it, I suggest we should remove the config option from
> > > defconfig in addition to this patch.
> >
> > I think the whole concept of the SBI console is a little dangerous.
> > It means that for one piece of physical hardware (usually the uart)
> > we have two entiries (the M-mode firmware and the OS) in control,
> > which tends to rarely end well.
> 
> I think the SBI console is only useful for early SOC bringup and early
> SOC debugging when most drivers are not available in upstream
> kernel. It cannot (and should not) be used in production deployments.

Usually the primary use-case for an abstract console interface is for 
desktop and server users.  Usually Linux distributions want a hardware 
platform-specific bootloader or BIOS to specify and control the console.  

Originally I suspect this was implemented in the SBI for semi-hosting 
purposes, but that's no longer really applicable.


- Paul