linux-kernel - Re: [PATCH v1 1/2] tty/vt: Use KVAL instead of use bit operation

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Message-ID: <Z7XGQ6muZoXmhJeD@example.org>
Date: Wed, 19 Feb 2025 12:53:39 +0100
From: Alexey Gladkov <legion@...nel.org>
To: Jiri Slaby <jirislaby@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v1 1/2] tty/vt: Use KVAL instead of use bit operation

On Wed, Feb 19, 2025 at 10:33:38AM +0100, Jiri Slaby wrote:
> On 19. 02. 25, 10:23, Alexey Gladkov wrote:
> > On Wed, Feb 19, 2025 at 07:24:52AM +0100, Jiri Slaby wrote:
> >> On 18. 02. 25, 13:29, Alexey Gladkov wrote:
> >>> The K_HANDLERS always gets KVAL as an argument. It is better to use the
> >>> KVAL macro itself instead of bit operation.
> >>>
> >>> Signed-off-by: Alexey Gladkov <legion@...nel.org>
> >>> ---
> >>>    drivers/tty/vt/keyboard.c | 4 ++--
> >>>    1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> >>> index 804355da46f5..7df041ac4d5c 100644
> >>> --- a/drivers/tty/vt/keyboard.c
> >>> +++ b/drivers/tty/vt/keyboard.c
> >>> @@ -885,7 +885,7 @@ static void k_shift(struct vc_data *vc, unsigned char value, char up_flag)
> >>>    		if (kbd->kbdmode == VC_UNICODE)
> >>>    			to_utf8(vc, npadch_value);
> >>>    		else
> >>> -			put_queue(vc, npadch_value & 0xff);
> >>> +			put_queue(vc, KVAL(npadch_value));
> >>
> >> While the mask is the same, this is not a kval, right?
> > 
> > I'm pretty sure it's KVAL, but to be honest I don't understand why it is
> > not done for to_utf8() as well. All values passed to to_utf8() must be
> > kval.
> 
> Not at all, it handles multibyte chars.
> 
> > We call to_utf8() in k_unicode, fn_enter (through k_spec), handle_diacr
> > (through k_deadunicode or k_unicode). All K_HANDLERS take KVAL as value.
> 
> Yes, but pass unicode multibyte to to_utf8().
> 
> > If I understand this code correctly, it is more correct to write it like
> > this:
> > 
> > --- a/drivers/tty/vt/keyboard.c
> > +++ b/drivers/tty/vt/keyboard.c
> > @@ -882,10 +882,11 @@ static void k_shift(struct vc_data *vc, unsigned char value, char up_flag)
> > 
> >          /* kludge */
> >          if (up_flag && shift_state != old_state && npadch_active) {
> > +               u32 kval = KVAL(npadch_value);
> >                  if (kbd->kbdmode == VC_UNICODE)
> > -                       to_utf8(vc, npadch_value);
> > +                       to_utf8(vc, kval);
> 
> Definitely not, as you want to pass that multibyte char in.

Ok. So I misunderstood this code. I will remove this change from the next
version.

-- 
Rgrds, legion