linux-kernel - Re: [PATCH 12/36] tty/vt: consolemap: use sizeof(*pointer) instead of sizeof(type)

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Message-ID: <8c809bd0-552d-8027-a1a7-96b77369d06e@linux.intel.com>
Date:   Tue, 7 Jun 2022 17:00:45 +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 12/36] tty/vt: consolemap: use sizeof(*pointer) instead
 of sizeof(type)

On Tue, 7 Jun 2022, Jiri Slaby wrote:

> It is preferred to use sizeof(*pointer) instead of sizeof(type). First,
> the type of the variable can change and one needs not change the former
> (unlike the latter). Second, the latter is error-prone due to (u16),
> (u16 *), and (u16 **) mixture here.
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

This seems fine but see the comments below which are not directly related 
to the change itself.

> ---
>  drivers/tty/vt/consolemap.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> index 097ab7d01f8b..79a62dcca046 100644
> --- a/drivers/tty/vt/consolemap.c
> +++ b/drivers/tty/vt/consolemap.c
> @@ -251,12 +251,12 @@ static void set_inverse_trans_unicode(struct vc_data *conp,
>  		return;
>  	q = p->inverse_trans_unicode;
>  	if (!q) {
> -		q = p->inverse_trans_unicode =
> -			kmalloc_array(MAX_GLYPH, sizeof(u16), GFP_KERNEL);
> +		q = p->inverse_trans_unicode = kmalloc_array(MAX_GLYPH,
> +				sizeof(*q), GFP_KERNEL);
>  		if (!q)
>  			return;
>  	}
> -	memset(q, 0, MAX_GLYPH * sizeof(u16));
> +	memset(q, 0, MAX_GLYPH * sizeof(*q));

Convert kmalloc_array into kcalloc and place memset() into else branch?

>  	for (i = 0; i < UNI_DIRS; i++) {
>  		p1 = p->uni_pgdir[i];
> @@ -478,8 +478,8 @@ static int con_unify_unimap(struct vc_data *conp, struct uni_pagedict *p)
>  					continue;
>  				if (!p1[k] || !q1[k])
>  					break;
> -				if (memcmp(p1[k], q1[k],
> -						UNI_ROW_GLYPHS * sizeof(u16)))
> +				if (memcmp(p1[k], q1[k], UNI_ROW_GLYPHS *
> +							sizeof(*p1[k])))
>  					break;
>  			}
>  			if (k < UNI_DIR_ROWS)
> @@ -505,7 +505,7 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>  	n = UNI_DIR(unicode);
>  	p1 = p->uni_pgdir[n];
>  	if (!p1) {
> -		p1 = p->uni_pgdir[n] = kcalloc(UNI_DIR_ROWS, sizeof(u16 *),
> +		p1 = p->uni_pgdir[n] = kcalloc(UNI_DIR_ROWS, sizeof(*p1),
>  				GFP_KERNEL);
>  		if (!p1)
>  			return -ENOMEM;
> @@ -514,11 +514,12 @@ con_insert_unipair(struct uni_pagedict *p, u_short unicode, u_short fontpos)
>  	n = UNI_ROW(unicode);
>  	p2 = p1[n];
>  	if (!p2) {
> -		p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(u16), GFP_KERNEL);
> +		p2 = p1[n] = kmalloc_array(UNI_ROW_GLYPHS, sizeof(*p2),
> +				GFP_KERNEL);
>  		if (!p2)
>  			return -ENOMEM;
>  		/* No glyphs for the characters (yet) */
> -		memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(u16));
> +		memset(p2, 0xff, UNI_ROW_GLYPHS * sizeof(*p2));

This could have been kcalloc'ed.


-- 
 i.