On 12 December 2017 at 12:41, Laszlo Ersek <ler...@redhat.com> wrote: > I agree. There's one user-visible complication: while with one UART, > it's not possible to mix things up, with two UARTs, users will > inevitably want to assign inverse roles to them, relative to what QEMU / > the firmware assigns originally. > > E.g. if one PL011 is redirected to a regular file (debug messages) and > the other one to stdio (console), there will be complaints that "I > wanted it the other way around". The redirection happens on the backend > (chardev) level, but the firmware won't see the difference on the > frontend (PL011) level. > > Is it possible to add a new property to the UART nodes in the DTB, like > "purpose"?
This is what the "chosen" stdout-path node in the DTB is for, but you said you didn't want to look at that :-) (it means "device to be used for boot console output".) > Or can we make a virt-arm policy that "first -serial is always ..., > second -serial is always ..."? Well, the first -serial will always be the 0x09000000 one that we have today, and the second -serial will be the other one (unless you have -machine secure=yes, in which case second -serial is the secure-only UART and third -serial is the second NS UART). Is this any different to the x86 case, where there are two UARTs at different IO port/IRQ locations? I think the only thing users really expect is that if you're using just the one serial port for anything then it's the first one. thanks -- PMM
