On Thu, Jan 19, 2017 at 05:12:15PM +0100, Manuel Schölling wrote: > On Thu, 2017-01-19 at 14:23 +0100, Greg KH wrote: > > On Fri, Jan 13, 2017 at 09:07:57PM +0100, Manuel Schölling wrote: > > > Add a scrollback buffers for each VGA console. The benefit is that > > > the scrollback history is not flushed when switching between consoles > > > but is persistent. The buffers are allocated on demand when a new > > > console is opened. > > > > > > This breaks tools like clear_console that rely on flushing the > > > scrollback history by switching back and forth between consoles > > > which is why this feature is disabled by default. > > > Use the escape sequence \e[3J instead for flushing the buffer. > > > > This issue is the one that makes me the most worried. Why doesn't > > clear_console() work anymore? Why doesn't it use \e[3J ? > > Well, clear_console() just switches from one console to another and > back again. It just assumes that the scrollback buffer is flushed when > switching. > My plan is to make a patch for clear_console() as soon as these patches > are in the kernel - it's chicken-and-egg problem. No need to wait, \e[3J is supported since Linux 2.6.39; the problem I spotted was that a previous version of your patch would break that. It is also safe to output that sequence to a terminal unconditionally: I've tested a number of terminals, they all either support it (most X terminals, our console) or silently ignore it. We can't, though, rely on terminfo to do so: it knows about this capability (which it calls "E3") for TERM=linux only since very recently. The TERM variable is also unreliable: it fails to carry over a serial link while blindly printing \e[3J works. As for patching clear_console, https://bugs.debian.org/845177 has a minimal fix; although for all setups supported by Debian that program could be be better replaced with just "printf '\e[3J\e[2J'" which would make it work on strictly more terminals than current code does. Same for distributions which copied clear_console (it originates from Ubuntu, maintained in Debian since then). Meow! -- Autotools hint: to do a zx-spectrum build on a pdp11 host, type: ./configure --host=zx-spectrum --build=pdp11 -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
