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Wed, 09 Apr 2025 09:59:17 -0700 (PDT) Received: from localhost ([216.228.127.131]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b02a11d298esm1284868a12.34.2025.04.09.09.59.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Apr 2025 09:59:16 -0700 (PDT) Date: Wed, 9 Apr 2025 12:59:14 -0400 From: Yury Norov To: Kuan-Wei Chiu Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, jk@ozlabs.org, joel@jms.id.au, eajames@linux.ibm.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, dmitry.torokhov@gmail.com, mchehab@kernel.org, awalls@md.metrocast.net, hverkuil@xs4all.nl, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, louis.peens@corigine.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, arend.vanspriel@broadcom.com, johannes@sipsolutions.net, gregkh@linuxfoundation.org, jirislaby@kernel.org, akpm@linux-foundation.org, jdelvare@suse.com, linux@roeck-us.net, alexandre.belloni@bootlin.com, pgaj@cadence.com, hpa@zytor.com, alistair@popple.id.au, linux@rasmusvillemoes.dk, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-fsi@lists.ozlabs.org, dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, oss-drivers@corigine.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, brcm80211@lists.linux.dev, brcm80211-dev-list.pdl@broadcom.com, linux-serial@vger.kernel.org, bpf@vger.kernel.org, jserv@ccns.ncku.edu.tw, Frank.Li@nxp.com, linux-hwmon@vger.kernel.org, linux-i3c@lists.infradead.org, david.laight.linux@gmail.com, andrew.cooper3@citrix.com, Yu-Chun Lin Subject: Re: [PATCH v4 01/13] bitops: Change parity8() to parity_odd() with u64 input and bool return type Message-ID: References: <20250409154356.423512-1-visitorckw@gmail.com> <20250409154356.423512-2-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250409154356.423512-2-visitorckw@gmail.com> On Wed, Apr 09, 2025 at 11:43:44PM +0800, Kuan-Wei Chiu wrote: > Redesign the parity8() helper as parity_odd(), changing its input type > from u8 to u64 to support broader use cases and its return type from > int to bool to clearly reflect the function's binary output. The > function now returns true for odd parity and false for even parity, > making its behavior more intuitive based on the name. > > Also mark the function with __attribute_const__ to enable better > compiler optimization, as the result depends solely on its input and > has no side effects. > > While more efficient implementations may exist, further optimization is > postponed until a use case in performance-critical paths arises. > > Co-developed-by: Yu-Chun Lin > Signed-off-by: Yu-Chun Lin > Signed-off-by: Kuan-Wei Chiu > --- > arch/x86/kernel/bootflag.c | 4 ++-- > drivers/hwmon/spd5118.c | 2 +- > drivers/i3c/master/dw-i3c-master.c | 2 +- > drivers/i3c/master/i3c-master-cdns.c | 2 +- > drivers/i3c/master/mipi-i3c-hci/dat_v1.c | 2 +- > include/linux/bitops.h | 19 ++++++++++++------- > 6 files changed, 18 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c > index 73274d76ce16..86aae4b2bfd5 100644 > --- a/arch/x86/kernel/bootflag.c > +++ b/arch/x86/kernel/bootflag.c > @@ -26,7 +26,7 @@ static void __init sbf_write(u8 v) > unsigned long flags; > > if (sbf_port != -1) { > - if (!parity8(v)) > + if (!parity_odd(v)) > v ^= SBF_PARITY; > > printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n", > @@ -57,7 +57,7 @@ static bool __init sbf_value_valid(u8 v) > { > if (v & SBF_RESERVED) /* Reserved bits */ > return false; > - if (!parity8(v)) > + if (!parity_odd(v)) > return false; > > return true; > diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c > index 358152868d96..15761f2ca4e9 100644 > --- a/drivers/hwmon/spd5118.c > +++ b/drivers/hwmon/spd5118.c > @@ -298,7 +298,7 @@ static umode_t spd5118_is_visible(const void *_data, enum hwmon_sensor_types typ > */ > static bool spd5118_vendor_valid(u8 bank, u8 id) > { > - if (parity8(bank) == 0 || parity8(id) == 0) > + if (!parity_odd(bank) || !parity_odd(id)) > return false; > > id &= 0x7f; > diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c > index 611c22b72c15..dc61d87fcd94 100644 > --- a/drivers/i3c/master/dw-i3c-master.c > +++ b/drivers/i3c/master/dw-i3c-master.c > @@ -867,7 +867,7 @@ static int dw_i3c_master_daa(struct i3c_master_controller *m) > master->devs[pos].addr = ret; > last_addr = ret; > > - ret |= parity8(ret) ? 0 : BIT(7); > + ret |= parity_odd(ret) ? 0 : BIT(7); > > writel(DEV_ADDR_TABLE_DYNAMIC_ADDR(ret), > master->regs + > diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c > index fd3752cea654..df14f978a388 100644 > --- a/drivers/i3c/master/i3c-master-cdns.c > +++ b/drivers/i3c/master/i3c-master-cdns.c > @@ -889,7 +889,7 @@ static u32 prepare_rr0_dev_address(u32 addr) > ret |= (addr & GENMASK(9, 7)) << 6; > > /* RR0[0] = ~XOR(addr[6:0]) */ > - ret |= parity8(addr & 0x7f) ? 0 : BIT(0); > + ret |= parity_odd(addr & 0x7f) ? 0 : BIT(0); > > return ret; > } > diff --git a/drivers/i3c/master/mipi-i3c-hci/dat_v1.c b/drivers/i3c/master/mipi-i3c-hci/dat_v1.c > index 85c4916972e4..d692a299607d 100644 > --- a/drivers/i3c/master/mipi-i3c-hci/dat_v1.c > +++ b/drivers/i3c/master/mipi-i3c-hci/dat_v1.c > @@ -114,7 +114,7 @@ static void hci_dat_v1_set_dynamic_addr(struct i3c_hci *hci, > dat_w0 = dat_w0_read(dat_idx); > dat_w0 &= ~(DAT_0_DYNAMIC_ADDRESS | DAT_0_DYNADDR_PARITY); > dat_w0 |= FIELD_PREP(DAT_0_DYNAMIC_ADDRESS, address) | > - (parity8(address) ? 0 : DAT_0_DYNADDR_PARITY); > + (parity_odd(address) ? 0 : DAT_0_DYNADDR_PARITY); > dat_w0_write(dat_idx, dat_w0); > } > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > index c1cb53cf2f0f..7c4c8afccef1 100644 > --- a/include/linux/bitops.h > +++ b/include/linux/bitops.h > @@ -230,35 +230,40 @@ static inline int get_count_order_long(unsigned long l) > } > > /** > - * parity8 - get the parity of an u8 value > - * @value: the value to be examined > + * parity_odd - get the parity of an u64 value > + * @val: the value to be examined > * > - * Determine the parity of the u8 argument. > + * Determine the parity of the u64 argument. > * > * Returns: > - * 0 for even parity, 1 for odd parity > + * false for even parity, true for odd parity > * > * Note: This function informs you about the current parity. Example to bail > * out when parity is odd: > * > - * if (parity8(val) == 1) > + * if (parity_odd(val)) > * return -EBADMSG; > * > * If you need to calculate a parity bit, you need to draw the conclusion from > * this result yourself. Example to enforce odd parity, parity bit is bit 7: > * > - * if (parity8(val) == 0) > + * if (!parity_odd(val)) > * val ^= BIT(7); > */ > -static inline int parity8(u8 val) > +#ifndef parity_odd Please don't add this guard. We've got no any arch implementations so far, and this is a dead code. Those adding arch code will also add the ifdefery. > +static inline __attribute_const__ bool parity_odd(u64 val) > { > /* > * One explanation of this algorithm: > * https://funloop.org/codex/problem/parity/README.html > */ > + val ^= val >> 32; > + val ^= val >> 16; > + val ^= val >> 8; > val ^= val >> 4; > return (0x6996 >> (val & 0xf)) & 1; > } > +#endif > > /** > * __ffs64 - find first set bit in a 64 bit word > -- > 2.34.1