linux-kernel - Re: [PATCH net-next 06/12] net: dsa: rzn1-a5psw: add Renesas RZ/N1 advanced 5 port switch driver

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 for Android: free password hash cracker in your pocket

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

Message-ID: <YllVsiN7YhaUkvQe@shell.armlinux.org.uk>
Date:   Fri, 15 Apr 2022 12:23:30 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Clément Léger <clement.leger@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Milan Stevanovic <milan.stevanovic@...com>,
        Jimmy Lalande <jimmy.lalande@...com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org,
        Jean-Pierre Geslin <jean-pierre.geslin@....se.com>,
        Phil Edworthy <phil.edworthy@...esas.com>
Subject: Re: [PATCH net-next 06/12] net: dsa: rzn1-a5psw: add Renesas RZ/N1
 advanced 5 port switch driver

On Fri, Apr 15, 2022 at 02:14:19PM +0300, Vladimir Oltean wrote:
> On Fri, Apr 15, 2022 at 12:02:14PM +0100, Russell King (Oracle) wrote:
> > On Fri, Apr 15, 2022 at 01:55:03PM +0300, Vladimir Oltean wrote:
> > > I meant that for a DSA switch driver is mandatory to call dsa_switch_shutdown()
> > > from your ->shutdown method, otherwise subtle things break, sorry for being unclear.
> > > 
> > > Please blindly copy-paste the odd pattern that all other DSA drivers use
> > > in ->shutdown and ->remove (with the platform_set_drvdata(dev, NULL) calls),
> > > like a normal person :)
> > 
> > Those platform_set_drvdata(, NULL) calls should be killed - the
> > driver model will set the driver data to NULL after ->remove has
> > been called - so having drivers also setting the driver data to
> > NULL is mere duplication.
> 
> I can see why you say that, but the reverse is not true.
> A driver can be removed from a device after said device has been shut
> down, and DSA does things in dsa_unregister_switch() and in
> dsa_switch_shutdown() that are incompatible with each other, so either
> one or the other should be called, but not both.

How would ->remove be called after ->shutdown has been called? Aren't
the two calls already exclusive - if ->remove has been called, the
device is no longer bound to the driver, so ->shutdown can't be called
for the device.  If ->shutdown has been called, the system is going
down, and userspace is probably already dead.

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