On Mon, Nov 17, 2008 at 10:42:46PM -0600, Timur Tabi wrote: > On Mon, Nov 17, 2008 at 6:40 PM, David Gibson > <[EMAIL PROTECTED]> wrote: > > > Because the udbg console works for kernel messages, but doesn't > > support a full tty interface, so you can't run userspace with only a > > udbg console. > > I still don't understand the point of your driver. You're just > routing hcalls to a udbg back-end. So if you have a driver that > supports udbg but not standard console or TTY, then you can use your > driver to get console/tty I/O. Is there a platform where such a setup > exists? All HVC drivers support console and TTY, as do all serial > drivers. So what platform would use your driver?
Like I said, it's a bringup hack. If you have hardware that's supported by an existing console driver, there's no reason you'd want it. For example, I've used it on a bringup prototype platform whose only I/O is a weird FPGA-implemented UART (not 8250 compatible, or even close). I implemented udbg callbacks as one of the first things I did, to get the early debugging. But eventually I got userspace up, and discovered that it wouldn't work on the udbg consoleuserspace won't work with the udbg console. I didn't really want to write another, more complex, driver for this strange UART, so I glued hvconsole to my existing udbg callbacks, giving me a userspace-capable console. Given the variety of strange I/O configurations in prototype and embedded platforms, I can't imagine this was a unique situation. So I've pushed my patch out, so anyone else in a similar situation can immediately turn their little udbg methods for whatever strange I/O they have into a fully-functional console. Maybe it's not something you'd want to go to release with, but it certainly simplifies life during bringup. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev