From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH net] net: phy: Decrement phy_fixed_addr during unregister Date: Fri, 24 Jun 2016 15:58:39 -0700 Message-ID: <576DBB1F.1030208@gmail.com> References: <1466808251-19588-1-git-send-email-f.fainelli@gmail.com> <20160624225527.GA1041@n2100.armlinux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, andrew@lunn.ch, thomas.petazzoni@free-electrons.com To: Russell King - ARM Linux Return-path: Received: from mail-pf0-f195.google.com ([209.85.192.195]:35177 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750876AbcFXW6l (ORCPT ); Fri, 24 Jun 2016 18:58:41 -0400 Received: by mail-pf0-f195.google.com with SMTP id t190so10342678pfb.2 for ; Fri, 24 Jun 2016 15:58:41 -0700 (PDT) In-Reply-To: <20160624225527.GA1041@n2100.armlinux.org.uk> Sender: netdev-owner@vger.kernel.org List-ID: On 06/24/2016 03:55 PM, Russell King - ARM Linux wrote: > On Fri, Jun 24, 2016 at 03:44:11PM -0700, Florian Fainelli wrote: >> If we have a system which uses fixed PHY devices and calls >> fixed_phy_register() then fixed_phy_unregister() we can exhaust the >> number of fixed PHYs available after a while, since we keep incrementing >> the variable phy_fixed_addr, but we never decrement it. >> >> This patch fixes that by decrementing phy_fixed_addr during >> fixed_phy_del(), and in order to do that, we need to move the >> phy_fixed_addr integer and its spinlock above that function. > > Is this really a good idea? In the sense that it is symetrical to the register code, probably. > > What if we have two fixed phys register, and the first one is > unregistered and a new one subsequently registered? > > First phy registered, gets address 0, phy_fixed_addr becomes 1. > Second phy registered, gets address 1, phy_fixed_addr becomes 2. > First phy is unregistered, phy_fixed_addr becomes 1. > Third phy registered, gets address 1, conflicts with the second phy. > > Obviously not a good outcome. > What would you suggest we do instead? Would switching to IDA/IDR give us better results for instance (I have not looked too closely yet)? -- Florian