From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: Device to write to all (serial) consoles Date: Sat, 3 Aug 2019 15:55:37 +0200 Message-ID: <20190803135537.GA1743@kroah.com> References: <32c2d26f-ec4a-b9a6-b42c-07b27f99ea28@molgen.mpg.de> <20190802160243.GA15484@kroah.com> <20190803132323.GB6703@angband.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190803132323.GB6703@angband.pl> Sender: linux-kernel-owner@vger.kernel.org To: Adam Borowski Cc: Paul Menzel , linux-serial@vger.kernel.org, Linux Kernel Mailing List , Donald Buczek List-Id: linux-serial@vger.kernel.org On Sat, Aug 03, 2019 at 03:23:23PM +0200, Adam Borowski wrote: > On Fri, Aug 02, 2019 at 09:59:06PM +0200, Paul Menzel wrote: > > On 02.08.19 18:02, Greg Kroah-Hartman wrote: > > > On Fri, Aug 02, 2019 at 03:23:08PM +0200, Paul Menzel wrote: > > > > On a lot of devices, like servers, you have more than one serial console, > > > > and you do not always know, how they are numbered. Therefore, we start a > > > > console on ttyS0 and ttyS1. > > > > Because the cable is always connected to the port on the back side, and > > sometimes the port in the front has ID 0, and the one in the back 1, and > > other times vice versa. We do not want to track that, and it would be > > convenient to just write to both ports. > > Sounds like an XY problem then: what you want is not writing to all ports, > but to have the port assignments stable (see also: disk device reordering). You can get that information from the symlinks in /dev/serial/ which udev creates.