From: Yury Norov <ynorov@nvidia•com>
To: Luiz Angelo Daros de Luca <luizluca@gmail•com>
Cc: "Andrew Lunn" <andrew@lunn•ch>,
"Vladimir Oltean" <olteanv@gmail•com>,
"David S. Miller" <davem@davemloft•net>,
"Eric Dumazet" <edumazet@google•com>,
"Jakub Kicinski" <kuba@kernel•org>,
"Paolo Abeni" <pabeni@redhat•com>,
"Simon Horman" <horms@kernel•org>,
"Linus Walleij" <linusw@kernel•org>,
"Alvin Šipraga" <alsi@bang-olufsen•dk>,
"Yury Norov" <yury.norov@gmail•com>,
"Rasmus Villemoes" <linux@rasmusvillemoes•dk>,
"Russell King" <linux@armlinux•org.uk>,
netdev@vger•kernel.org, linux-kernel@vger•kernel.org
Subject: Re: [net-next PATCH 04/10] bitfield.h: add FIELD_WIDTH()
Date: Tue, 31 Mar 2026 22:15:49 -0400 [thread overview]
Message-ID: <acx_1dOF3EjvGt4B@yury> (raw)
In-Reply-To: <20260331-realtek_forward-v1-4-44fb63033b7e@gmail.com>
On Tue, Mar 31, 2026 at 08:00:04PM -0300, Luiz Angelo Daros de Luca wrote:
> Some hardware stores logical fields split across multiple registers,
> requiring partial values to be reassembled using shifts and masks.
>
> Add FIELD_WIDTH(), a helper that returns the number of contiguous bits
> covered by a bitfield mask. This allows callers to determine how much a
> partial value needs to be shifted when reconstructing a field.
>
> This complements FIELD_MAX() and FIELD_FIT(), and avoids reimplementing
> bit counting logic in drivers.
>
> Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail•com>
> ---
> include/linux/bitfield.h | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
> index 54aeeef1f0ec..8d6c1c309c3b 100644
> --- a/include/linux/bitfield.h
> +++ b/include/linux/bitfield.h
> @@ -111,6 +111,19 @@
> (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
> })
>
> +/**
> + * FIELD_WIDTH() - return the width of a bitfield
> + * @_mask: shifted mask defining the field's length and position
> + *
> + * Returns the number of contiguous bits covered by @_mask.
> + * This corresponds to the bit width of FIELD_MAX(@_mask).
> + */
> +#define FIELD_WIDTH(_mask) \
Please no underscored names unless necessary.
> + ({ \
> + __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_WIDTH: "); \
> + __bf_shf(~FIELD_MAX(_mask)); \
> + })
I believe, this should be:
#define FIELD_WIDTH(mask) ({ \
__BF_FIELD_CHECK_MASK(mask, 0ULL, "FIELD_WIDTH: "); \
HWEIGHT(mask); \
})
Thanks,
Yury
> +
> /**
> * FIELD_FIT() - check if value fits in the field
> * @_mask: shifted mask defining the field's length and position
>
> --
> 2.53.0
>
next prev parent reply other threads:[~2026-04-01 2:20 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-31 23:00 [net-next PATCH 00/10] net: dsa: realtek: rtl8365mb: bridge offloading and VLAN support Luiz Angelo Daros de Luca
2026-03-31 23:00 ` [net-next PATCH 01/10] net: dsa: tag_rtl8_4: update format description Luiz Angelo Daros de Luca
2026-04-07 7:33 ` Linus Walleij
2026-03-31 23:00 ` [net-next PATCH 02/10] net: dsa: realtek: rtl8365mb: set STP state to disabled early Luiz Angelo Daros de Luca
2026-03-31 23:00 ` [net-next PATCH 03/10] net: dsa: realtek: rtl8365mb: prepare for multiple source files Luiz Angelo Daros de Luca
2026-04-07 7:35 ` Linus Walleij
2026-03-31 23:00 ` [net-next PATCH 04/10] bitfield.h: add FIELD_WIDTH() Luiz Angelo Daros de Luca
2026-04-01 2:15 ` Yury Norov [this message]
2026-04-02 4:00 ` Luiz Angelo Daros de Luca
2026-04-02 9:27 ` David Laight
2026-04-02 13:52 ` Yury Norov
2026-04-02 22:21 ` David Laight
2026-04-03 14:09 ` Luiz Angelo Daros de Luca
2026-04-03 16:18 ` Yury Norov
2026-04-04 14:54 ` David Laight
2026-04-04 15:12 ` David Laight
2026-04-02 13:45 ` Yury Norov
2026-03-31 23:00 ` [net-next PATCH 05/10] net: dsa: realtek: rtl8365mb: add table lookup interface Luiz Angelo Daros de Luca
2026-04-07 7:43 ` Linus Walleij
2026-03-31 23:00 ` [net-next PATCH 06/10] net: dsa: realtek: rtl8365mb: add VLAN support Luiz Angelo Daros de Luca
2026-04-01 2:27 ` Yury Norov
2026-04-02 2:45 ` Luiz Angelo Daros de Luca
2026-04-02 14:22 ` Yury Norov
2026-04-07 7:59 ` Linus Walleij
2026-04-10 7:05 ` Luiz Angelo Daros de Luca
2026-04-10 7:36 ` Linus Walleij
2026-04-22 4:10 ` Luiz Angelo Daros de Luca
2026-04-27 18:07 ` Luiz Angelo Daros de Luca
2026-04-27 20:11 ` Linus Walleij
2026-04-28 9:26 ` Gabor Juhos
2026-03-31 23:00 ` [net-next PATCH 07/10] net: dsa: realtek: rtl8365mb: add port_bridge_{join,leave} Luiz Angelo Daros de Luca
2026-04-07 8:11 ` Linus Walleij
2026-04-22 5:42 ` Luiz Angelo Daros de Luca
2026-03-31 23:00 ` [net-next PATCH 08/10] net: dsa: realtek: rtl8365mb: add FDB support Luiz Angelo Daros de Luca
2026-04-07 9:11 ` Linus Walleij
2026-04-22 6:56 ` Luiz Angelo Daros de Luca
2026-03-31 23:00 ` [net-next PATCH 09/10] net: dsa: realtek: rtl8365mb: add bridge port flags Luiz Angelo Daros de Luca
2026-04-07 9:20 ` Linus Walleij
2026-04-22 6:06 ` Luiz Angelo Daros de Luca
2026-03-31 23:00 ` [net-next PATCH 10/10] net: dsa: tag_rtl8_4: set KEEP flag Luiz Angelo Daros de Luca
2026-04-07 9:22 ` Linus Walleij
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