netdev - Re: [PATCH 09/15] net: phy: delay PHY driver probe until PHY registration

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200624165016.GA1551@shell.armlinux.org.uk>
Date:   Wed, 24 Jun 2020 17:50:16 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Mark Brown <broonie@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Iyappan Subramanian <iyappan@...amperecomputing.com>,
        Keyur Chudgar <keyur@...amperecomputing.com>,
        Quan Nguyen <quan@...amperecomputing.com>,
        Frank Rowand <frowand.list@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        netdev <netdev@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        Fabien Parent <fparent@...libre.com>,
        Stephane Le Provost <stephane.leprovost@...iatek.com>,
        Pedro Tsai <pedro.tsai@...iatek.com>,
        Andrew Perepech <andrew.perepech@...iatek.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 09/15] net: phy: delay PHY driver probe until PHY
 registration

On Wed, Jun 24, 2020 at 09:06:28AM -0700, Florian Fainelli wrote:
> On 6/24/2020 6:48 AM, Bartosz Golaszewski wrote:
> > I didn't expect to open such a can of worms...
> > 
> > This has evolved into several new concepts being proposed vs my
> > use-case which is relatively simple. The former will probably take
> > several months of development, reviews and discussions and it will
> > block supporting the phy supply on pumpkin boards upstream. I would
> > prefer not to redo what other MAC drivers do (phy-supply property on
> > the MAC node, controlling it from the MAC driver itself) if we've
> > already established it's wrong.
> 
> You are not new to Linux development, so none of this should come as a
> surprise to you. Your proposed solution has clearly short comings and is
> a hack, especially around the PHY_ID_NONE business to get a phy_device
> only then to have the real PHY device ID. You should also now that "I
> need it now because my product deliverable depends on it" has never been
> received as a valid argument to coerce people into accepting a solution
> for which there are at review time known deficiencies to the proposed
> approach.

It /is/ a generic issue.  The same problem exists for AMBA Primecell
devices, and that code has an internal deferred device list that it
manages.  See drivers/amba/bus.c, amba_deferred_retry_func(),
amba_device_try_add(), and amba_device_add().

As we see more devices gain this property, it needs to be addressed
in a generic way, rather than coming up with multiple bus specific
implementations.

Maybe struct bus_type needs a method to do the preparation to add
a device (such as reading IDs etc), which is called by device_add().
If that method returns -EPROBE_DEFER, the device gets added to a
deferred list, which gets retried when drivers are successfully
probed.  Possible maybe?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!