Re: [PATCH] gpio: pcf857x: restore the initial line state of all pcf lines

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi,

On Wednesday 18 March 2015 05:51 PM, Linus Walleij wrote:
On Mon, Mar 16, 2015 at 9:46 AM, Kishon Vijay Abraham I <kishon@xxxxxx> wrote:
On Wednesday 14 January 2015 05:28 PM, Linus Walleij wrote:

#include <linux/reboot.h>

static int foo_reboot_handler(struct notifier_block *this,
                                  unsigned long code,
                                  void *unused)
{
          pr_crit("do some last minute stuff\n");
          return NOTIFY_OK;
}

static struct notifier_block foo_reboot_notifier = {
          .notifier_call = foo_reboot_handler,
};

register_reboot_notifier(&foo_reboot_notifier);


Added debug prints and found the reboot notifier gets invoked before the
shutdown handler which means some stuff can be done after this reboot
notifier:-(

Specify exactly what stuff may happen after the reboot notifier.

okay, it's assumed the device may be used (active) till the shutdown handler
of that particular device is called.

In this particular case we are restoring the initial line state of all pcf
lines even though we don't know if the devices connected to it are still being
active, which might cause a contention as explained by NM [1]

If the reboot notifier gets invoked after the shutdown handler then we could
be sure that restoring the initial line state of the pcf lines wouldn't affect
the devices connected to it.

Thanks
Kishon

[1] -> http://www.spinics.net/lists/linux-mmc/msg29855.html

Of course stuff happens both before and after the reboot
notifier, the question is exactly what, that may conflict with this.

Yours,
Linus Walleij

--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux SPI]     [Linux Kernel]     [Linux ARM (vger)]     [Linux ARM MSM]     [Linux Omap]     [Linux Arm]     [Linux Tegra]     [Fedora ARM]     [Linux for Samsung SOC]     [eCos]     [Linux Fastboot]     [Gcc Help]     [Git]     [DCCP]     [IETF Announce]     [Security]     [Linux MIPS]     [Yosemite Campsites]

  Powered by Linux