On 06/07/2017 01:14 PM, Ben Hutchings wrote: > On Wed, 2017-06-07 at 18:10 +0100, Ben Hutchings wrote: >>> CONFIG_SERIAL_8250_RUNTIME_UARTS=16 >> That seems reasonable. > [...] > > Actually, having looked further at what this does, I'm unconvinced > about changing it. It can always be overridden through the > '8250.nr_uarts' kernel parameter where needed.
On my system, this meant that I could not use the serial console to do an install. Doing console=ttyS4 on the command-line didn't work because the kernel didn't support anything after ttyS3. I guess we could also teach folks to add nr_uarts=8 (or whatever) to their kernel command-line, which also works around this. But, it would be handy to have it work by default. I don't think there's really any overhead to raising 'nr_uarts', either. It makes some (unimportant) loops longer, but I don't think there's any real downsides. FWIW, a lot of distros make it pretty large. My Ubuntu desktop has it set to 48 and Fedora evidently sets it to 32.
