On Fri, Jun 24, 2016 at 03:58:39PM -0700, Florian Fainelli wrote: > 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)?
I would expect an IDA to be suitable, because the IDA would track which indexes (==addresses) are currently in-use. If you want to go further, using an IDR would allow fixed_mdio_read() to find the right fixed_phy struct without needing to loop over fmb->phys. Whether that's worth it or not depends if you have a large number of fixed phys. I suspect we're talking about small quantities here though. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
