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. > > > > > > Signed-off-by: Manuel Schölling <manuel.schoelling@xxxxxx> > > > Reviewed-by: Andrey Utkin <andrey_utkin@xxxxxxxxxxxx> > > > Tested-by: Andrey Utkin <andrey_utkin@xxxxxxxxxxxx> > > > Tested-by: Adam Borowski <kilobyte@xxxxxxxxxx> > > > --- > > > drivers/video/console/Kconfig | 25 +++++++- > > > drivers/video/console/vgacon.c | 142 ++++++++++++++++++++++++++--- > > > ------------ > > > 2 files changed, 111 insertions(+), 56 deletions(-) > > > > > > diff --git a/drivers/video/console/Kconfig > > > b/drivers/video/console/Kconfig > > > index c3f1fb9ee820..f500e58f7636 100644 > > > --- a/drivers/video/console/Kconfig > > > +++ b/drivers/video/console/Kconfig > > > @@ -43,9 +43,28 @@ config VGACON_SOFT_SCROLLBACK_SIZE > > > range 1 1024 > > > default "64" > > > help > > > - Enter the amount of System RAM to allocate for the > > > scrollback > > > - buffer. Each 64KB will give you approximately 16 80x25 > > > - screenfuls of scrollback buffer > > > + Enter the amount of System RAM to allocate for > > > scrollback > > > + buffers of VGA consoles. Each 64KB will give you > > > approximately > > > + 16 80x25 screenfuls of scrollback buffer. > > > + > > > +config VGACON_SOFT_SCROLLBACK_PERSISTENT > > > + bool "Persistent Scrollback History for each console" > > > + depends on VGACON_SOFT_SCROLLBACK > > > + default n > > > + help > > > + Say Y here if the scrollback history should persist when > > > switching > > > + between consoles. Otherwise, the scrollback history will > > > be flushed > > > + each time the console is switched. > > > + > > > + This feature might break your tool of choice to flush > > > the scrollback > > > + buffer, e.g. clear(1) will work fine but Debian's > > > clear_console(1) > > > + will be broken, which might cause security issues. > > > + You can use the escape sequence \e[3J instead if this > > > feature is > > > + activated. > > > > 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. I'd recommend that patch get to clear_console() first, having it use the new escape sequence, if it isn't supported, shouldn't cause any problems, right? thanks, greg k-h -- 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
