linux-kernel - Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off

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] [day] [month] [year] [list]

Date:   Tue, 20 Jun 2017 17:29:59 +0200
From:   Oleksij Rempel <ore@...gutronix.de>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        devicetree@...r.kernel.org, Fabio Estevam <fabio.estevam@....com>,
        kernel@...gutronix.de, Liam Girdwood <lgirdwood@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH v5 3/6] kernel/reboot.c: export pm_power_off_prepare

On Tue, Jun 20, 2017 at 05:37:06PM +0300, Leonard Crestez wrote:
> On Tue, 2017-06-20 at 07:01 +0200, Oleksij Rempel wrote:
> > 
> > On 19.06.2017 13:35, Leonard Crestez wrote:
> > > 
> > > On Mon, 2017-06-19 at 07:02 +0200, Oleksij Rempel wrote:
> > > > 
> > > > Export pm_power_off_prepare. It is needed to implement power off on
> > > > Freescale/NXP iMX6 based boards with external power management
> > > > integrated circuit (PMIC).
> > > > 
> > > > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > > > ---
> > > >  kernel/reboot.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/kernel/reboot.c b/kernel/reboot.c
> > > > index bd30a973fe94..a6903bf772c7 100644
> > > > --- a/kernel/reboot.c
> > > > +++ b/kernel/reboot.c
> > > > @@ -49,6 +49,7 @@ int reboot_force;
> > > >   */
> > > > 
> > > >  void (*pm_power_off_prepare)(void);
> > > > +EXPORT_SYMBOL(pm_power_off_prepare);
> > > > 
> > > Could you register a reboot notifier in the pfuze driver instead? Right
> > > now the only user of pm_power_off_prepare is ACPI so this alternative
> > > seems less intrusive.
> > hm... in this case i will need to make sure that reboot handler is not 
> > executed on reboot. This will make code looks strange. Which is opposite 
> > of your comment in other email about strange standby code for power off :)
> > Should i really do this?
> 
> A reboot handler receives a parameter to differentiate between reboot
> and shutdown so it would be easy. Isn't it preferable to use an
> existing mechanism instead of exporting a new symbol?
> 
> But maybe somebody else will Ack this, I don't particularly insist on
> changing this.

I just need to make sure, nothing else will do some thing unexpected
with PMIC. Don't forget we use same PMIC_STBY_REQ signal for stanby,
suspend to RAM and for power off. Entering wrong state in wrong moment
will be fatal. This is why I use last possible step before pm_power_off.

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |