linux-kernel - Re: [PATCH 4/5] fbcon: Avoid hard-coding built-in font charcount

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Date:   Tue, 27 Oct 2020 20:13:53 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Peilin Ye <yepeilin.cs@...il.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] fbcon: Avoid hard-coding built-in font charcount

On Tue, Oct 27, 2020 at 12:37:29PM -0400, Peilin Ye wrote:
> fbcon_startup() and fbcon_init() are hard-coding the number of characters
> of our built-in fonts as 256. Recently, we included that information in
> our kernel font descriptor `struct font_desc`, so use `font->charcount`
> instead of a hard-coded value.
> 
> This patch depends on patch "Fonts: Add charcount field to font_desc".
> 
> Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>

So I think this is correct, but it also doesn't do a hole lot yet. fbcon.c
still has tons of hard-coded 256 all over, and if (p->userfont).

I think if we instead set vc->vc_font.charcount both in fbcon_init and in
fbcon_do_set_font (probably just replace the userfont parameter with
font_charcount for now), then we could replace these all with
vc->vc_font.charcount. And the code would already improve quite a bit I
think.

With just this change here I think we have even more inconsistency, since
for built-in fonts vc->vc_font.charcount is now set correctly, but for
userfonts we need to instead look at FNTCHARCNT(vc->vc_font.data).

We'd still need to maintain p->userfont because of the refcount chaos, but
that is much more work.

Or do I miss something here?
-Daniel

> ---
>  drivers/video/fbdev/core/fbcon.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index cef437817b0d..e563847991b7 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -1004,7 +1004,7 @@ static const char *fbcon_startup(void)
>  		vc->vc_font.width = font->width;
>  		vc->vc_font.height = font->height;
>  		vc->vc_font.data = (void *)(p->fontdata = font->data);
> -		vc->vc_font.charcount = 256; /* FIXME  Need to support more fonts */
> +		vc->vc_font.charcount = font->charcount;
>  	} else {
>  		p->fontdata = vc->vc_font.data;
>  	}
> @@ -1083,8 +1083,7 @@ static void fbcon_init(struct vc_data *vc, int init)
>  			vc->vc_font.width = font->width;
>  			vc->vc_font.height = font->height;
>  			vc->vc_font.data = (void *)(p->fontdata = font->data);
> -			vc->vc_font.charcount = 256; /* FIXME  Need to
> -							support more fonts */
> +			vc->vc_font.charcount = font->charcount;
>  		}
>  	}
>  
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch