linux-kernel - Re: [PATCH] vt: make the default cursor shape configurable

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Date:	Tue, 10 Nov 2009 15:26:05 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pavel Machek <pavel@....cz>
Cc:	Daniel Mack <daniel@...aq.de>,
	David Newall <davidn@...idnewall.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Clemens Ladisch <clemens@...isch.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vt: make the default cursor shape configurable

On Tue, 10 Nov 2009 22:09:41 +0100
Pavel Machek <pavel@....cz> wrote:

> On Mon 2009-11-09 23:09:44, Daniel Mack wrote:
> > On Tue, Nov 10, 2009 at 04:28:03AM +1030, David Newall wrote:
> > > Daniel Mack wrote:
> > > > And even if the cursor behaviour is changable at runtime, I don't see
> > > > why it shouldn't have a selectable compile time default. Which is what
> > > > the patch adds.
> > > 
> > > 
> > > It seems like adding cruft to the kernel that is just as effectively
> > > available at run-time. Where does it end? Do we eventually add bash to
> > > the kernel?
> > 
> > One more thing:
> > 
> > Clemens' last patch didn't add anything to the kernel's binary size.
> > It didn't slow down anything either, as there is no run-time condition
> > evaluation. It just makes something configurable which was hard
> > coded before. So where's the cruft?
> 
> The number of configs to test just got bigger. 100% bigger in
> fact. Every single developer will have to answer 'do you want blinking
> cursor?' when your patch is merged.
> 
> config options _are_ expensive.
> 

Plus it's nice not to have to rebuild and reinstall the kernel to flip
a single bit...

The module_param() approach seems OK to me.


The initial patch was busted, IMO:

> @@ -1288,7 +1296,8 @@ static void fbcon_cursor(struct vc_data *vc, int mode)
> 	int y;
>  	int c = scr_readw((u16 *) vc->vc_pos);
> 
> -	if (fbcon_is_inactive(vc, info) || vc->vc_deccm != 1)
> +	if (fbcon_is_inactive(vc, info) || vc->vc_deccm != 1 ||
> +	    fbcon_disable_cursor)
> 		return;

this will disable the cursor forever, afacit.  So if you boot with the
fbcon_disable_cursor option, you cannot later enable the cursor.

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