From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 1/5] phylib: don't return NULL from get_phy_device() Date: Thu, 28 Apr 2016 00:03:38 +0200 Message-ID: <4737525.3QtvmUGfR0@wuerfel> References: <56219623.1S7UfcqQqc@wasted.cogentembedded.com> <20160427194932.GF29024@lunn.ch> <57211C81.4000903@cogentembedded.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Andrew Lunn , Vivien Didelot , "David S. Miller" , f.fainelli@gmail.com, netdev@vger.kernel.org, kernel@savoirfairelinux.com To: Sergei Shtylyov Return-path: Received: from mout.kundenserver.de ([217.72.192.73]:52875 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbcD0WEH (ORCPT ); Wed, 27 Apr 2016 18:04:07 -0400 In-Reply-To: <57211C81.4000903@cogentembedded.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wednesday 27 April 2016 23:09:37 Sergei Shtylyov wrote: > Hello. > > On 04/27/2016 10:49 PM, Andrew Lunn wrote: > > >> Sergei Shtylyov writes: > >> > >>> Arnd Bergmann asked that get_phy_device() returns either NULL or the error > >>> value, not both on error. Do as he said, return ERR_PTR(-ENODEV) instead > >>> of NULL when the PHY ID registers read as all ones. > >>> > >>> Suggested-by: Arnd Bergmann > >>> Signed-off-by: Sergei Shtylyov > >>> > >>> --- > >>> drivers/net/phy/phy_device.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> Index: net-next/drivers/net/phy/phy_device.c > >>> =================================================================== > >>> --- net-next.orig/drivers/net/phy/phy_device.c > >>> +++ net-next/drivers/net/phy/phy_device.c > >>> @@ -529,7 +529,7 @@ struct phy_device *get_phy_device(struct > >>> > >>> /* If the phy_id is mostly Fs, there is no device there */ > >>> if ((phy_id & 0x1fffffff) == 0x1fffffff) > >>> - return NULL; > >>> + return ERR_PTR(-ENODEV); > >>> > >>> return phy_device_create(bus, addr, phy_id, is_c45, &c45_ids); > >>> } > > > > This change is wrong, it needs reverting, or the call sights need > > fixing to expect ENODEV. > > So this function had a good reason to return NULL, as it turned out... :-( > > > The point is, the device not being there is not an error, with respect > > to the code calling this function. > > > > It gets called by mdiobus_scan() > > > > struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr) > > { > > struct phy_device *phydev; > > int err; > > > > phydev = get_phy_device(bus, addr, false); > > if (IS_ERR(phydev) || phydev == NULL) > > return phydev; > > > > So before, we return NULL, if the device was not there. Now we return > > ERR_PTR(-ENODEV). > > > > This is being called by: > > > > int __mdiobus_register(struct mii_bus *bus, struct module *owner) > > { > > struct mdio_device *mdiodev; > > ... > > for (i = 0; i < PHY_MAX_ADDR; i++) { > > if ((bus->phy_mask & (1 << i)) == 0) { > > struct phy_device *phydev; > > > > phydev = mdiobus_scan(bus, i); > > if (IS_ERR(phydev)) { > > err = PTR_ERR(phydev); > > goto error; > > } > > } > > } > > > > This is treating ERR_PTR(-ENODEV) as a fatal error, where as before > > IS_ERR(NULL) would be false and it would continue scanning other > > addresses on the bus. > > Thank you for the detailed analysis! (And shame on me for the lack of it.) > > > Please revert this, or fix all the callsites such that ENODEV is not a > > fatal error. > > OK, I'll do what DaveM decides. I found one other user that remains broken: pxa168_init_phy() looks wrong before and after the patch: pep->phy = mdiobus_scan(pep->smi_bus, pep->phy_addr); if (!pep->phy) return -ENODEV; err = phy_connect_direct(dev, pep->phy, pxa168_eth_adjust_link, pep->phy_intf); as phy_connect_direct() will go on and dereference an error pointer. This should check for IS_ERR(), and with the patches applied, we can drop the !pep->phy check. Arnd