linux-kernel - Re: [PATCH] fbcon: Fix vc attr at deinit

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Date:   Tue, 3 Jan 2017 17:49:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Jiri Slaby <jslaby@...e.cz>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fbcon: Fix vc attr at deinit

On Tue, Jan 03, 2017 at 04:03:22PM +0100, Takashi Iwai wrote:
> fbcon can deal with vc_hi_font_mask (the upper 256 chars) and adjust
> the vc attrs dynamically when vc_hi_font_mask is changed at
> fbcon_init().  When the vc_hi_font_mask is set, it remaps the attrs in
> the existing console buffer with one bit shift up (for 9 bits), while
> it remaps with one bit shift down (for 8 bits) when the value is
> cleared.  It works fine as long as the font gets updated after fbcon
> was initialized.
> 
> However, we hit a bizarre problem when the console is switched to
> another fb driver (typically from vesafb or efifb to drmfb).  At
> switching to the new fb driver, we temporarily rebind the console to
> the dummy console, then rebind to the new driver.  During the
> switching, we leave the modified attrs as is.  Thus, the new fbcon
> takes over the old buffer as if it were to contain 8 bits chars
> (although the attrs are still shifted for 9 bits), and effectively
> this results in the yellow color texts instead of the original white
> color, as found in the bugzilla entry below.
> 
> An easy fix for this is to re-adjust the attrs before leaving the
> fbcon at con_deinit callback.  Since the code to adjust the attrs is
> already present in the current fbcon code, in this patch, we simply
> factor out the relevant code, and call it from fbcon_deinit().
> 
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1000619
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
>  drivers/video/console/fbcon.c | 67 ++++++++++++++++++++++++++-----------------
>  1 file changed, 40 insertions(+), 27 deletions(-)

So this is an old bug?  Should it go to stable kernels?

And am I the fbcon maintainer now?

thanks,

greg k-h