* Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [090318 12:26]:
> On Wed, Mar 18, 2009 at 11:28:06AM -0700, Tony Lindgren wrote:
> > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [090316 15:22]:
> > > On Mon, Mar 16, 2009 at 07:40:24PM +0200, Juha Yrjola wrote:
> > > > Russell King - ARM Linux wrote:
> > > >
> > > >> Right. You are aware that there is already a mechanism for doing this
> > > >> in the generic kernel (obviously not)?
> > > >
> > > > I am. Unfortunately, glibc fails to support this mechanism, as you say.
> > > > I didn't want to start making such intrusive changes for our trivial
> > > > need.
> > >
> > > Yes, glibc sucks with that - they hide the Linux reboot syscall.
> > > Luckily, it is accessible via the syscall() interface:
> > >
> > > #include <linux/reboot.h>
> > >
> > > int sys_reboot(const char *cmd)
> > > {
> > > return syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2C,
> > > LINUX_REBOOT_CMD_RESTART2, cmd);
> > > }
> > >
> > > >> sys_reboot() with LINUX_REBOOT_CMD_RESTART2 takes a string in addition
> > > >> to the standard parameters. This string is passed into machine_restart()
> > > >> which we currently ignore. If LINUX_REBOOT_CMD_RESTART is used, this
> > > >> string is NULL.
> > > >>
> > > >> We could change machine_restart() to pass this parameter through to
> > > >> arm_pm_restart() and ultimately down to arch_reset().
> > > >
> > > > Sure. With RESTART2, I could've even used the reboot notifier chain with
> > > > an OMAP3-specific driver to store the string.
> > >
> > > The notifier chain is called in any case.
> > >
> > > > Are you suggesting to get rid of reboot_mode altogether? If not, could
> > > > we still have the sysfs mechanism? A one-character reboot_mode would be
> > > > plenty enough for us.
> > >
> > > No, reboot mode tells _how_ to perform the reboot - whether that be
> > > by hardware reset, gpio reset or a soft call via the reset address.
> > > It's not supposed to tell the boot loader what to do.
> >
> > So if the reboot mode can't be used for this.. Should we change Juha's
> > sysfs interface patch to store something else like bootloader_mode?
> >
> > I guess we cannot use kexec for this either?
>
> Why not use the mechanism that's already there as I've already pointed
> out?
Sorry I misunderstood, I thought you did not want to use reboot_mode
for this at all..
To recap, so we change machine_restart() like you described above, and then
this patch is still valid, except to update the description.
Juha, does that sound OK to you?
> Yes, glibc might be fscked in the head over the reboot() prototype but
> that's easy to work-around as I've demonstrated.
Yeah sounds good to me.
Tony
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