linux-kernel - Re: [PATCH v10 2/3] watchdog: introduce CONFIG_WATCHDOG_OPEN

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Message-ID: <20190607183926.GC32475@roeck-us.net>
Date:   Fri, 7 Jun 2019 11:39:26 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Cc:     "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Jonathan Corbet <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Esben Haabendal <esben@...bendal.dk>,
        Jerry Hoemann <jerry.hoemann@....com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: Re: [PATCH v10 2/3] watchdog: introduce CONFIG_WATCHDOG_OPEN_TIMEOUT

On Wed, Jun 05, 2019 at 02:06:43PM +0000, Rasmus Villemoes wrote:
> This allows setting a default value for the watchdog.open_timeout
> commandline parameter via Kconfig.
> 
> Some BSPs allow remote updating of the kernel image and root file
> system, but updating the bootloader requires physical access. Hence, if
> one has a firmware update that requires relaxing the
> watchdog.open_timeout a little, the value used must be baked into the
> kernel image itself and cannot come from the u-boot environment via the
> kernel command line.
> 
> Being able to set the initial value in .config doesn't change the fact
> that the value on the command line, if present, takes precedence, and is
> of course immensely useful for development purposes while one has
> console acccess, as well as usable in the cases where one can make a
> permanent update of the kernel command line.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>

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

> ---
>  Documentation/watchdog/watchdog-parameters.txt | 8 ++++----
>  drivers/watchdog/Kconfig                       | 9 +++++++++
>  drivers/watchdog/watchdog_dev.c                | 5 +++--
>  3 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt
> index 32d3606caa65..ec919dc895ff 100644
> --- a/Documentation/watchdog/watchdog-parameters.txt
> +++ b/Documentation/watchdog/watchdog-parameters.txt
> @@ -11,10 +11,10 @@ modules.
>  The watchdog core parameter watchdog.open_timeout is the maximum time,
>  in seconds, for which the watchdog framework will take care of pinging
>  a running hardware watchdog until userspace opens the corresponding
> -/dev/watchdogN device. A value of 0 (the default) means an infinite
> -timeout. Setting this to a non-zero value can be useful to ensure that
> -either userspace comes up properly, or the board gets reset and allows
> -fallback logic in the bootloader to try something else.
> +/dev/watchdogN device. A value of 0 means an infinite timeout. Setting
> +this to a non-zero value can be useful to ensure that either userspace
> +comes up properly, or the board gets reset and allows fallback logic
> +in the bootloader to try something else.
>  
>  
>  -------------------------------------------------
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index ffe754539f5a..a8bd621e12f8 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -58,6 +58,15 @@ config WATCHDOG_HANDLE_BOOT_ENABLED
>  	  the watchdog on its own. Thus if your userspace does not start fast
>  	  enough your device will reboot.
>  
> +config WATCHDOG_OPEN_TIMEOUT
> +	int "Timeout value for opening watchdog device"
> +	default 0
> +	help
> +	  The maximum time, in seconds, for which the watchdog framework takes
> +	  care of pinging a hardware watchdog.  A value of 0 means infinite. The
> +	  value set here can be overridden by the commandline parameter
> +	  "watchdog.open_timeout".
> +
>  config WATCHDOG_SYSFS
>  	bool "Read different watchdog information through sysfs"
>  	help
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index e4b51db48f0e..334b810db2cf 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -88,7 +88,7 @@ static struct kthread_worker *watchdog_kworker;
>  static bool handle_boot_enabled =
>  	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
>  
> -static unsigned open_timeout;
> +static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
>  
>  static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
>  {
> @@ -1214,4 +1214,5 @@ MODULE_PARM_DESC(handle_boot_enabled,
>  
>  module_param(open_timeout, uint, 0644);
>  MODULE_PARM_DESC(open_timeout,
> -	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default=0)");
> +	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
> +	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");