linux-kernel - Re: [PATCH 10/36] tty/vt: consolemap: introduce UNI

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Date:   Tue, 7 Jun 2022 16:47:20 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Jiri Slaby <jslaby@...e.cz>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 10/36] tty/vt: consolemap: introduce UNI_*() macros

On Tue, 7 Jun 2022, Jiri Slaby wrote:

> The code currently does shift, OR, and AND logic directly in the code.
> It is not much obvious what happens there. Therefore define four macros
> for that purpose and use them in the code. We use GENMASK() so that it
> is clear which bits serve what purpose:
> - UNI_GLYPH: bits  0.. 5
> - UNI_ROW:   bits  6..10
> - UNI_DIR:   bits 11..31
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> ---
>  drivers/tty/vt/consolemap.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> index 016c1a0b4290..e5fd225e87bd 100644
> --- a/drivers/tty/vt/consolemap.c
> +++ b/drivers/tty/vt/consolemap.c
> @@ -190,6 +190,11 @@ static int inv_translate[MAX_NR_CONSOLES];
>  #define UNI_DIR_ROWS	32U
>  #define UNI_ROW_GLYPHS	64U
>  
> +#define UNI_DIR(uni)		( (uni)                   >> 11)
> +#define UNI_ROW(uni)		(((uni) & GENMASK(10, 6)) >>  6)

This is opencoding what FIELD_GET() does. Maybe just define these as 
masks and use FIELD_GET in the code below.

> +#define UNI_GLYPH(uni)		( (uni) & GENMASK( 5, 0))
> +#define UNI(dir, row, glyph)	(((dir) << 11) | ((row) << 6) | (glyph))
>
>  /**
>   * struct uni_pagedict -- unicode directory
>   *
> @@ -265,7 +270,7 @@ static void set_inverse_trans_unicode(struct vc_data *conp,
>  				glyph = p2[k];
>  				if (glyph >= 0 && glyph < MAX_GLYPH
>  					       && q[glyph] < 32)
> -					q[glyph] = (i << 11) | (j << 6) | k;
> +					q[glyph] = UNI(i, j, k);
>  			}
>  		}
>  	}
> @@ -497,7 +502,7 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>  	int i, n;
>  	u16 **p1, *p2;
>  
> -	n = unicode >> 11;
> +	n = UNI_DIR(unicode);
>  	p1 = p->uni_pgdir[n];
>  	if (!p1) {
>  		p1 = p->uni_pgdir[n] = kmalloc_array(UNI_DIR_ROWS,
> @@ -508,7 +513,7 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>  			p1[i] = NULL;
>  	}
>  
> -	n = (unicode >> 6) & 0x1f;
> +	n = UNI_ROW(unicode);
>  	p2 = p1[n];
>  	if (!p2) {
>  		p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(u16), GFP_KERNEL);
> @@ -518,7 +523,7 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>  		memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(u16));
>  	}
>  
> -	p2[unicode & 0x3f] = fontpos;
> +	p2[UNI_GLYPH(unicode)] = fontpos;
>  	
>  	p->sum += (fontpos << 20U) + unicode;
>  
> @@ -788,7 +793,7 @@ int con_get_unimap(struct vc_data *vc, ushort ct, ushort __user *uct, struct uni
>  						continue;
>  					if (ect < ct) {
>  						unilist[ect].unicode =
> -							(i<<11) | (j<<6) | k;
> +							UNI(i, j, k);
>  						unilist[ect].fontpos = *p2;
>  					}
>  					ect++;
> @@ -857,9 +862,9 @@ conv_uni_to_pc(struct vc_data *conp, long ucs)
>  		return -3;
>  
>  	p = *conp->vc_uni_pagedir_loc;
> -	if ((p1 = p->uni_pgdir[ucs >> 11]) &&
> -	    (p2 = p1[(ucs >> 6) & 0x1f]) &&
> -	    (h = p2[ucs & 0x3f]) < MAX_GLYPH)
> +	if ((p1 = p->uni_pgdir[UNI_DIR(ucs)]) &&
> +	    (p2 = p1[UNI_ROW(ucs)]) &&
> +	    (h = p2[UNI_GLYPH(ucs)]) < MAX_GLYPH)
>  		return h;
>  
>  	return -4;		/* not found */
> 

-- 
 i.