From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jiri Slaby <jirislaby-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH] fbcon: Disable accelerated scrolling
Date: Thu, 29 Oct 2020 06:42:39 +0100
Message-ID: <997267e5-40c1-2aaf-235a-ff14f2d101e6@kernel.org>
References: <20201028160600.3752105-1-daniel.vetter@ffwll.ch>
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To: Daniel Vetter <daniel.vetter-/w4YWyX8dFk@public.gmane.org>, DRI Development <dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>, Tetsuo Handa <penguin-kernel-JPay3/Yim36HaxMnTkn67Xf5DAMn2ifp@public.gmane.org>, nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, "Gustavo A. R. Silva" <gustavoars-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Peter Rosin <peda-koto5C5qi+TLoDKTGw+V6w@public.gmane.org>, George Kennedy <george.kennedy-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Tomi Valkeinen <tomi.valkeinen-l0cyMroinI0@public.gmane.org>, Ben Skeggs <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Daniel Vetter <daniel.vetter-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Nathan Chancellor <natechancellor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Peilin Ye <yepeilin.cs-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
List-Id: nouveau.vger.kernel.org

On 28. 10. 20, 17:06, Daniel Vetter wrote:
> So ever since syzbot discovered fbcon, we have solid proof that it's
> full of bugs. And often the solution is to just delete code and remove
> features, e.g.  50145474f6ef ("fbcon: remove soft scrollback code").
...
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -1147,11 +1147,13 @@ static void fbcon_init(struct vc_data *vc, int init)
>   
>   	ops->graphics = 0;
>   
> -	if ((cap & FBINFO_HWACCEL_COPYAREA) &&
> -	    !(cap & FBINFO_HWACCEL_DISABLED))
> -		p->scrollmode = SCROLL_MOVE;
> -	else /* default to something safe */
> -		p->scrollmode = SCROLL_REDRAW;
> +	/*
> +	 * No more hw acceleration for fbcon.
> +	 *
> +	 * FIXME: Garabge collect all the now dead code after sufficient time

If you go this non-invasive path, then only a nit here: "Garbage"

thanks,
-- 
js
suse labs