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Miller" , Florian Fainelli , Heiner Kallweit , Rob Herring , Frank Rowand , Srinivas Kandagatla , Maxime Ripard , Alban Bedel Subject: Re: Handling of EPROBE_DEFER in of_get_mac_address [Was: Re: [PATCH v2 3/4] net: macb: Drop nvmem_get_mac_address usage] Message-ID: <20190501135417.GB19809@lunn.ch> References: <1556456002-13430-1-git-send-email-ynezz@true.cz> <1556456002-13430-4-git-send-email-ynezz@true.cz> <20190428165637.GJ23059@lunn.ch> <20190428210814.GA346@meh.true.cz> <20190428213640.GB10772@lunn.ch> <20190429075514.GB346@meh.true.cz> <20190429130248.GC10772@lunn.ch> <20190430141335.GC346@meh.true.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190430141335.GC346@meh.true.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 30, 2019 at 04:13:35PM +0200, Petr Štetiar wrote: > Andrew Lunn [2019-04-29 15:02:48]: > > Hi Andrew, > > > > My understanding of -PROBE_DEFER is, that it needs to be propagated back from > > > the driver's probe callback/hook to the upper device/driver subsystem in order > > > to be moved to the list of pending drivers and considered for probe later > > > again. This is not going to happen in any of the current drivers, thus it will > > > probably still always result in random MAC address in case of -EPROBE_DEFER > > > error from the nvmem subsystem. > > > > All current drivers which don't look in NVMEM don't expect > > EPROBE_DEFER. > > once there's NVMEM wired in of_get_mac_address, one can simply use it, nothing > is going to stop the potential user of doing so and if EPROBE_DEFER isn't > propagated from the driver back to the upper device driver subsytem, it's > probably going to end with random MAC address in some (very rare?) cases. Hi Petr There is no simple answer here. If we add EPROBE_DEFER support to all the current drivers using of_get_mac_address(), we are likely to break something. Regressions are bad. If somebody does add NVMEM properties to a device which does not currently have them, and it fails, that it just bad testing, not a regressions. So i would keep it KISS. Allow of_get_mac_address() to return an error, but don't modify current drivers to look for it. Andrew