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

[Jiri Slaby]

On 07. 06. 22, 16:00, Ilpo Järvinen wrote:
> 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@xxxxxxx>
>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
>
> 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?

IMO, the way it is now is more obvious.

> > @@ -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.

Why would you zero it before setting it to 0xff?

thanks,
--
js
suse labs