linux-kernel - Re: [PATCH v3] console: Add persistent scrollback buffers for all VGA consoles

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Date:   Tue, 27 Sep 2016 12:58:42 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Manuel Schölling <manuel.schoelling@....de>
Cc:     plagnioj@...osoft.com, tomi.valkeinen@...com, jslaby@...e.cz,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] console: Add persistent scrollback buffers for all
 VGA consoles

On Mon, Sep 19, 2016 at 12:06:57AM +0200, 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.
> 
> It always annoys me when I switch back to a console and I can just
> read half of an error backtrace. This should fix issues like these.
> 
> 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@....de>
> ---
> Changes in v3:
>   - Add config option for this feature
>   - Fallback to old scrollback buffer if kcalloc() fails
>   - Remove ioctl() call again and add documentation about existing
>     escape sequence to flush the scrollback buffer
> Changes in v2:
>   - Add ioctl() call to flush scrollback buffer
>   - (Patch v2 was not labeled as such, sorry)
> ---
>  drivers/video/console/Kconfig  |  23 +++++-
>  drivers/video/console/vgacon.c | 160 +++++++++++++++++++++++++++--------------
>  2 files changed, 128 insertions(+), 55 deletions(-)

I need someone else to at least test this, and give an acked-by for
it...

thanks,

greg k-h