Messages in this thread | | | Date | Fri, 17 Feb 2006 14:39:42 +0300 | Subject | Re: [PATCH] SIIG 8-port serial boards support | From | Andrey Panin <> |
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On 034, 02 03, 2006 at 09:24:36 +0000, Russell King wrote: > On Fri, Feb 03, 2006 at 12:13:08PM +0300, Andrey Panin wrote: > > On 033, 02 02, 2006 at 08:17:35 +0000, Russell King wrote: > > > As I've said many a time, we need a generic way to set different hand- > > > shaking modes. I've suggested using some spare bits in termios in the > > > past, but nothing ever came of that - folk lose interest at that point.
No wonder they do. Extra bits are not a problem, but for 8250.c we need some way to glue subdrivers with serial8250_set_termios(). Callback in uart_port structure ?
> > IMHO there is no need to userspace visible changes to support RS485 on > > these cards, because some of them are RS485 only and some have jumpers > > for individual ports. There is nothing that userspace can configure. > > We only need to set two bits in ACR according to card type and jumper > > settings and UART will drive RS485 transiever transparently. > > In this particular case you may be right, but I'm looking at the bigger > picture, where plain 16550's may be used for RS485.
Common way to use plain 16550 for RS485 is to wire transiever to the RTS and force userspace to use RTS/CTS flow control. I doubt there are many other sane way to do it.
> There are drivers which want to implement their own private ioctl to > enable RS485 mode. What I'm saying is that we should have one solution, > not multiple solutions to this problem. When we have such a solution, > your RS485 card will be able to fit into that model.
But it will need a way to pass ACR value anyway :)
-- Andrey Panin | Linux and UNIX system administrator pazke@donpac.ru | PGP key: wwwkeys.pgp.net [unhandled content-type:application/pgp-signature] | |