# Re: \[PATCH\] net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx\_read\_raw\_eeprom - From: Oleksij Rempel \ - Date: 2025-10-01 08:38:50 - List: netdev - Page: https://ratatoskr.run/netdev/2025/10/3237265 - Thread: https://ratatoskr.run/netdev/2025/09/3236054/t.md ```text On Wed, Oct 01, 2025 at 02:01:24PM +0530, Bhanu Seshu Kumar Valluri wrote: > 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. Ok, thank you! Can you please add similar change to lan78xx_write_raw_eeprom. syzbot will find it soon or later. -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | ```