From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: [PATCH] cfg80211: use IDA to allocate wiphy indeces Date: Fri, 29 Jun 2018 12:01:04 -0700 Message-ID: <278cfd54-204b-2ff7-a8d2-575a01151667@candelatech.com> References: <20180621012945.185705-1-briannorris@chromium.org> <1530258140.3481.4.camel@sipsolutions.net> <20180629184847.GA251207@ban.mtv.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org To: Brian Norris , Johannes Berg Return-path: In-Reply-To: <20180629184847.GA251207@ban.mtv.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 06/29/2018 11:48 AM, Brian Norris wrote: > Hi Johannes, > > On Fri, Jun 29, 2018 at 09:42:20AM +0200, Johannes Berg wrote: >> On Wed, 2018-06-20 at 18:29 -0700, Brian Norris wrote: >>> It's annoying to see the phy index increase arbitrarily, just because a >>> device got removed and re-probed (e.g., during a device reset, or due to >>> probe testing). We can use the in-kernel index allocator for this, >>> instead of just an increasing counter. >> >> I can understand that it's somewhat annoying to people, but it was >> actually done on purpose to avoid userspace talking to the wrong device. > > Hmm, interesting. I'm not dead-set on this patch, so if there are good > reasons to reject it, I won't fret. > >> Imagine you have some userspace process running that has remembered the >> wiphy index to use it to talk to nl80211, and now underneath the device >> goes away and reappears. This process should understand that situation, >> and handle it accordingly, rather than being blind to the reset. > > How is this different from the wlan (netdev) device naming? We allow > 'wlan0' to leave and return under the same name. Isn't the right answer > that user space should be listening for udev and/or netlink events? > > Brian > For what it is worth, we use udev to rename the phyX to wiphyZ devices based on their MAC address, and that seems to work OK. I can't think of any reason why user-space would need the phy index number to increase as modules are loaded/unloaded though. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com