lkml.org 
[lkml]   [2019]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] watchdog: make nowayout sysfs file writable
From
Date
On 11/5/19 12:51 PM, Rasmus Villemoes wrote:
> It can be useful to delay setting the nowayout feature for a watchdog
> device. Moreover, not every driver (notably gpio_wdt) implements a
> nowayout module parameter/otherwise respects CONFIG_WATCHDOG_NOWAYOUT,
> and modifying those drivers carries a risk of causing a regression for
> someone who has two watchdog devices, sets CONFIG_WATCHDOG_NOWAYOUT
> and somehow relies on the gpio_wdt driver being ignorant of
> that (i.e., allowing one to gracefully close a gpio_wdt but not the
> other watchdog in the system).
>
> So instead, simply make the nowayout sysfs file writable. Obviously,
> setting nowayout is a one-way street.
>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> v2: drop redundant "current" variable and !!.
>
> .../ABI/testing/sysfs-class-watchdog | 9 ++++++--
> drivers/watchdog/watchdog_dev.c | 21 ++++++++++++++++++-
> 2 files changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-watchdog b/Documentation/ABI/testing/sysfs-class-watchdog
> index 675f9b537661..9860a8b2ba75 100644
> --- a/Documentation/ABI/testing/sysfs-class-watchdog
> +++ b/Documentation/ABI/testing/sysfs-class-watchdog
> @@ -17,8 +17,13 @@ What: /sys/class/watchdog/watchdogn/nowayout
> Date: August 2015
> Contact: Wim Van Sebroeck <wim@iguana.be>
> Description:
> - It is a read only file. While reading, it gives '1' if that
> - device supports nowayout feature else, it gives '0'.
> + It is a read/write file. While reading, it gives '1'
> + if the device has the nowayout feature set, otherwise
> + it gives '0'. Writing a '1' to the file enables the
> + nowayout feature. Once set, the nowayout feature
> + cannot be disabled, so writing a '0' either has no
> + effect (if the feature was already disabled) or
> + results in a permission error.
>
> What: /sys/class/watchdog/watchdogn/state
> Date: August 2015
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index dbd2ad4c9294..d3bdcb144657 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -452,7 +452,26 @@ static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
>
> return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
> }
> -static DEVICE_ATTR_RO(nowayout);
> +
> +static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> + struct watchdog_device *wdd = dev_get_drvdata(dev);
> + unsigned int value;
> + int ret;
> +
> + ret = kstrtouint(buf, 0, &value);
> + if (ret)
> + return ret;
> + if (value > 1)
> + return -EINVAL;
> + /* nowayout cannot be disabled once set */
> + if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
> + return -EPERM;
> + watchdog_set_nowayout(wdd, value);
> + return len;
> +}
> +static DEVICE_ATTR_RW(nowayout);
>
> static ssize_t status_show(struct device *dev, struct device_attribute *attr,
> char *buf)
>

\
 
 \ /
  Last update: 2019-11-06 15:38    [W:0.085 / U:0.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site