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Wed, 01 Oct 2025 01:31:39 -0700 (PDT) Message-ID: <7cc900dd-a49a-4f37-88e9-6794e92fc7d4@gmail.com> Date: Wed, 1 Oct 2025 14:01:24 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx_read_raw_eeprom To: Oleksij Rempel Cc: Jakub Kicinski , Thangaraj.S@microchip.com, Rengarajan.S@microchip.com, UNGLinuxDriver@microchip.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+62ec8226f01cb4ca19d9@syzkaller.appspotmail.com References: <20250930084902.19062-1-bhanuseshukumar@gmail.com> <20250930173950.5d7636e2@kernel.org> <5f936182-6a69-4d9a-9cec-96ec93aab82a@gmail.com> Content-Language: en-US From: Bhanu Seshu Kumar Valluri In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/10/25 13:54, Oleksij Rempel wrote: > On Wed, Oct 01, 2025 at 01:40:56PM +0530, Bhanu Seshu Kumar Valluri wrote: >> On 01/10/25 13:12, Oleksij Rempel wrote: >>> Hi, >>> >>> On Wed, Oct 01, 2025 at 10:07:21AM +0530, Bhanu Seshu Kumar Valluri wrote: >>>> On 01/10/25 06:09, Jakub Kicinski wrote: >>>>> On Tue, 30 Sep 2025 14:19:02 +0530 Bhanu Seshu Kumar Valluri wrote: >>>>>> + if (dev->chipid == ID_REV_CHIP_ID_7800_) { >>>>>> + int rc = lan78xx_write_reg(dev, HW_CFG, saved); >>>>>> + /* If USB fails, there is nothing to do */ >>>>>> + if (rc < 0) >>>>>> + return rc; >>>>>> + } >>>>>> + return ret; >>>>> >>>>> I don't think you need to add and handle rc here separately? >>>>> rc can only be <= so save the answer to ret and "fall thru"? >>>> >>>> The fall thru path might have been reached with ret holding EEPROM read timeout >>>> error status. So if ret is used instead of rc it might over write the ret with 0 when >>>> lan78xx_write_reg returns success and timeout error status would be lost. >>> >>> Ack, I see. It may happen if communication with EEPROM will fail. The same >>> would happen on write path too. Is it happened with real HW or it is >>> some USB emulation test? For me it is interesting why EEPROM is timed >>> out. >> >> The sysbot's log with message "EEPROM read operation timeout" confirms that EEPROM read >> timeout occurring. I tested the same condition on EVB-LAN7800LC by simulating >> timeout during probe. > > Do you simulating timeout during probe by modifying the code, or it is > real HW issue? > On my real hardware timeout didn't occur. So I simulated it once by modifying the code to confirm the BUG. The BUG has occurred confirming syzbot finding. Thanks.