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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Richard Cochran , Simon Horman , Pascal Eberhard , =?utf-8?Q?Miqu=C3=A8l?= Raynal , Thomas Petazzoni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Maxime Chevallier Subject: Re: [PATCH net-next v6 1/9] net: dsa: microchip: Add support for KSZ8463 global irq Message-ID: <20260305095656.vlyaztv6nbdqrmil@skbuf> References: <20260304-ksz8463-ptp-v6-0-3f4c47954c71@bootlin.com> <20260304-ksz8463-ptp-v6-1-3f4c47954c71@bootlin.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: <20260304-ksz8463-ptp-v6-1-3f4c47954c71@bootlin.com> On Wed, Mar 04, 2026 at 11:18:52AM +0100, Bastien Curutchet (Schneider Electric) wrote: > @@ -2890,14 +2899,18 @@ static irqreturn_t ksz_irq_thread_fn(int irq, void *dev_id) > unsigned int nhandled = 0; > struct ksz_device *dev; > unsigned int sub_irq; > - u8 data; > + u16 data; > int ret; > u8 n; > > dev = kirq->dev; > > - /* Read interrupt status register */ > - ret = ksz_read8(dev, kirq->reg_status, &data); > + /* > + * Most of the KSZ switches have a 8-bits long interrupt status > + * register, but the KSZ8463 has a 16-bits long one. The overread here > + * is safe because we only iterate over kirq->nirqs in the below loop. FWIW, this isn't the only thing making an overread "safe". If the adjacent register also has "clear on read" semantics, that's not good. I can't tell whether that's the case here, though. There are just too many hardware variations to check for. I just wanted to point out that the reasoning is incomplete. > + */ > + ret = ksz_read16(dev, kirq->reg_status, &data); I guess I don't fully understand the KSZ_REGMAP_TABLE() layer, but I have a concern here. Take the normal ksz_girq_setup() case for example, where we set kirq->reg_status = REG_SW_PORT_INT_STATUS__1. With ksz_read8(), we read u8 data from address REG_SW_PORT_INT_STATUS__1. With ksz_read16(), how do we read u16 data? Don't we read data[15:8] from REG_SW_PORT_INT_STATUS__1 and data[7:0] from REG_SW_PORT_INT_STATUS__1 + 1? But then we still look at the 0..kirq->nirq bits, effectively from address REG_SW_PORT_INT_STATUS__1 + 1 now? Or are the registers at address i 16-bits wide without spilling over into address i+1? Because if that's the case, I don't understand the comment/concern about overreading. > if (ret) > goto out;