[systemd-devel] [PATCH 2/2] vconsole-setup: setup negative conditional on uml

[Kay Sievers]

On Sat, Jul 20, 2013 at 12:25 PM, Ramkumar Ramachandra
<artagnon at gmail.com> wrote:
> Kay Sievers wrote:
>> I would rather see vconsole to detect the mess and silently give up,
>> instead of adding exotic options for really weird faked and wrong tty0
>> setups.
>
> um Linux lacks VT102 emulation, and this is a documented fact.

Providing tty0 and not working VT doesn't sound right. There is
already a condition in the unit file that would make sure to do the
right thing.

Documenting it doesn't make it less fake, there should just be no tty0
if VTs are not working.

> Therefore, your code:
>
>         unsigned char data[1];
>
>         data[0] = TIOCL_GETFGCONSOLE;
>         return ioctl(fd, TIOCLINUX, data) >= 0;
>
> is guaranteed to fail.  Not because something went "wrong", or due to
> some "mess" or "fakeness", but because it was perfectly expected.  I
> discussed this on LKML, and posted an explanation about this already
> [1].

It's just about the existence of tty0 which indicates a working VT.

> That said, I don't know what to do about
> systemd-vconsole-setup.service: I just followed Zbyszek's suggestion.
> Penalizing um Linux for not doing VT102 emulation, and always failing
> a service seems user-unfriendly to me.

It's not about failing it, that would be ugly, sure. Vconsole can just
give up and return 0 if it finds a tt0 that actually isn't a tty0.

That would work for all future mis-implementations of tty0 too,
without adding more conditions. :)

Kay