On Tue, 15 Jun 2021, Greg Kroah-Hartman wrote: > > Add a hook for `uart_report_port' to let serial ports report extra > > properties beyond `irq' and `base_baud'. Use it with the 8250 backend > > to report extra baud rates supported above the base rate for ports with > > the UPF_MAGIC_MULTIPLIER property, so that people have a way to find out > > that they are supported with their system, e.g.: [...] > Ick, really? What relies on this print message? Why do we need a whole > new uart port hook for this? As I noted, perhaps too briefly, in the commit description (see the last sentence above) people need to be made aware of the extra baud rates above `base_baud' supported, or otherwise they'll have no way to figure out they can use them. Reporting tweaked `base_baud' would I think cause confusion from the inconsistency with the TIOCGSERIAL/TIOCSSERIAL ioctls (e.g. `setserial'), and the sysfs flags: $ cat /sys/class/tty/ttyS[0-2]/flags 0x10010040 0x10010040 0x90000040 $ (here from a Malta board) are IMO too obscure for anyone to figure this out (bit 16 means the two extra baud rates are supported). As explained with 1/5 we could set `base_baud' to 460800 instead and hardcode bit 15 of the divisor to 1, relying on undocumented Super I/O IC behaviour, but that would require more exhaustive verification than I am able to do with just a single board and IC type and revision. > Isn't there some other way for your specific variant to print out > another message if you really want to do something "odd" like this? There's always another way. :) How about? serial8250.0: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A serial8250.0: ttyS0 extra baud rates supported: 230400, 460800 > And you did not document what your new change did anywhere in the tree, > so people are going to be confused. We've been somewhat terse about things, but you're probably right here. Sorry about that. > I've taken the other patches here, but not this one. Thanks. I've posted an alternative printing a message like above, with some commentary. Let me know if that makes you feel more convinced. Maciej
