Re: [PATCH v4 02/13] media: media/test_drivers: Replace open-coded parity calculation with parity_odd()

Kuan-Wei Chiu
2025-04-09T18:23:21Z

On Wed, Apr 09, 2025 at 01:03:42PM -0400, Yury Norov wrote:
> On Wed, Apr 09, 2025 at 11:43:45PM +0800, Kuan-Wei Chiu wrote:
> > Refactor parity calculations to use the standard parity_odd() helper.
> > This change eliminates redundant implementations.
> >
> > Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com>
> > Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
> > Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> > ---
> > drivers/media/test-drivers/vivid/vivid-vbi-gen.c | 8 ++------
> > 1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/test-drivers/vivid/vivid-vbi-gen.c b/drivers/media/test-drivers/vivid/vivid-vbi-gen.c
> > index 70a4024d461e..5e1b7b1742e4 100644
> > --- a/drivers/media/test-drivers/vivid/vivid-vbi-gen.c
> > +++ b/drivers/media/test-drivers/vivid/vivid-vbi-gen.c
> > @@ -5,6 +5,7 @@
> > * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
> > */
> >
> > +#include <linux/bitops.h>
> > #include <linux/errno.h>
> > #include <linux/kernel.h>
> > #include <linux/ktime.h>
> > @@ -165,12 +166,7 @@ static const u8 vivid_cc_sequence2[30] = {
> >
> > static u8 calc_parity(u8 val)
> > {
> > - unsigned i;
> > - unsigned tot = 0;
> > -
> > - for (i = 0; i < 7; i++)
> > - tot += (val & (1 << i)) ? 1 : 0;
> > - return val | ((tot & 1) ? 0 : 0x80);
> > + return val | (parity_odd(val) ? 0 : 0x80);
>
> So, if val == 0 than parity_odd(val) is also 0, and this can be
> simplified just to:
> return parity(val) ? 0 : 0x80;
> Or I miss something?
>
If val == 0x01, the return value of calc_parity() will remain 0x01.
If changed to return parity_odd(val) ? 0 : 0x80;, the return value will
be changed to 0x00.

Regards,
Kuan-Wei

> > }
> >
> > static void vivid_vbi_gen_set_time_of_day(u8 *packet)
> > --
> > 2.34.1