Re: Kernel debugging / drivers (was: USB keyboard driver the GNU Mach)

[Samuel Thibault]

Hello,

I agree that having a in-kernel USB keyboard driver makes sense for the
debugger.

As for the interaction with userland USB support, I don't think we can
share the access to the same USB chip, so when the kernel driver is
running the userland driver can't run.  One could say that when the USB
driver is to drive a USB keyboard used for kernel debugging, we don't
have access to that USB bus from userland.  Or we could add in interface
for USB userland to access the USB bus driven by the kernel.  At least
I'd say it shouldn't be the preferred way, and only there for kernel
debugging.

Olaf Buddenhagen, on Sat 19 Mar 2016 21:58:53 +0100, wrote:
> On Mon, Feb 29, 2016 at 12:41:43PM +0100, Justus Winter wrote:
> 
> > While we generally want to move away from drivers in the kernel, it
> > might indeed be nice to have a keyboard driver inside it for kdb.
> 
> Hm, this is an interesting point. I haven't actually considered keyboard
> drivers up till now; but there is an even bigger problem: as soon as you
> are no longer running VGA text mode, kdb won't work without huge amounts
> of graphics driver code in the kernel.

I don't think we need to worry about debugging while not in VGA text
mode.  Linux has never proposed anything for that case.

Samuel