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Date: Thu, 31 Mar 2022 10:28:04 +0200 From: Michael Walle <michael@...le.cc> To: "Russell King (Oracle)" <linux@...linux.org.uk> Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "David S . Miller" <davem@...emloft.net>, Xu Liang <lxu@...linear.com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH RFC net-next 2/5] net: phy: support indirect c45 access in get_phy_c45_ids() Am 2022-03-30 18:18, schrieb Russell King (Oracle): > On Wed, Mar 23, 2022 at 11:14:11PM +0100, Michael Walle wrote: >> I actually had that. But mmd_phy_indirect() doesn't check >> the return code and neither does the __phy_write_mmd() it >> actually deliberatly sets "ret = 0". So I wasn't sure. If you >> are fine with a changed code flow in the error case, then sure. >> I.e. mmd_phy_indirect() always (try to) do three accesses; with >> error checks it might end after the first. If you are fine >> with the error checks, should __phy_write_mmd() also check the >> last mdiobus_write()? > > The reason for that goes back to > commit a59a4d1921664da63d801ba477950114c71c88c9 > phy: add the EEE support and the way to access to the MMD > registers. > > and to maintain compatibility with that; if we start checking for > errors now, we might trigger a kernel regression sadly. I see that this is the commit which introduced the mmd_phy_indirect() function, but I don't see why there is no return code checking. Unlike now, there is a check for the last read (the one who reads MII_MMD_DATA). That read which might return garbage if any write has failed before - or if the bus is completely dead, return an error. Current code will just return 0. In any case, I don't have a strong opinion here. I just don't see how that function could be reused while adding error checks and without making it ugly, so I've just duplicated it. Maybe something like this: static int __phy_mmd_indirect_common(struct mii_bus *bus, int prtad, int devad, int addr, bool check_rc) { int ret; /* Write the desired MMD Devad */ ret = __mdiobus_write(bus, phy_addr, MII_MMD_CTRL, devad); if (check_rc && ret) return ret; /* Write the desired MMD register address */ ret = __mdiobus_write(bus, phy_addr, MII_MMD_DATA, regnum); if (check_rc && ret) return ret; /* Select the Function : DATA with no post increment */ ret = __mdiobus_write(bus, phy_addr, MII_MMD_CTRL, devad | MII_MMD_CTRL_NOINCR); if (check_rc && ret) return ret; return 0; } int __phy_mmd_indirect(struct mii_bus *bus, int prtad, int devad, int addr) { return __phy_mmd_indirect_common(bus, prtad, devad, addr, true); } /* some function doc about deliberatly no error checking.. */ void __phy_mmd_indirect_legacy(struct mii_bus *bus, int prtad, int devad, int addr) { __phy_mmd_indirect_common(bus, prtad, devad, addr, false); } should the last two functions be static inline? -michael
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