Re: [PATCH v1 1/3] vt: keyboard, use GENMAASK()/BIT() macros instead of open coded variants

[Jiri Slaby]

On 06. 11. 20, 17:06, Andy Shevchenko wrote:
> On Fri, Nov 6, 2020 at 5:35 PM David Laight <David.Laight@xxxxxxxxxx> wrote:
> > From: Andy Shevchenko
> > > Sent: 06 November 2020 14:36
> > >
> > > There are few places when GENMASK() or BIT() macro is suitable and makes code
> > > easier to understand.
> > ...
> > > -     if ((d & ~0xff) == BRL_UC_ROW) {
> > > -             if ((ch & ~0xff) == BRL_UC_ROW)
> > > +     if ((d & ~GENMASK(7, 0)) == BRL_UC_ROW) {
> > > +             if ((ch & ~GENMASK(7, 0)) == BRL_UC_ROW)
> > >                        return d | ch;
> >
> > Do you really think that makes it more readable?
>
> Yes. Because this tells explicitly how many bits are used for metadata
> vs. data.

No, because ~0xff is clearly what it is. GENMASK(7, 0) is:
1) longer to read & parse by brain with result: "GENMASK undefined"
2) terrible in this particular use case

Another instance of an even worse switch:
-		if (arg & ~0x77)
+		if (arg & ~(GENMASK(6, 4) | GENMASK(2, 0)))

OTOH, the switch to BIT is legit in all cases except the comparisons 
with keycode:
-	if (keycode > 127)
+	if (keycode >= BIT(7))
-		if (keycode < 128) {
+		if (keycode < BIT(7)) {

That's horrid and non-sense too.

sorry,
--
js
suse labs