linux-kernel - Re: [char-misc-next, v4, 5/7] watchdog: mei_wdt: register wd device only if required

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Date:	Sun, 17 Jan 2016 09:13:08 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	"Winkler, Tomas" <tomas.winkler@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Alexander Usyskin <alexander.usyskin@...el.com>,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [char-misc-next, v4, 5/7] watchdog: mei_wdt: register wd device
 only if required

Hi Tomas,

On Fri, Jan 08, 2016 at 12:49:25AM +0200, Winkler, Tomas wrote:
> From: Alexander Usyskin <alexander.usyskin@...el.com>
> 
> For Intel Broadwell and newer platforms, the ME device can inform
> the host whether the watchdog functionality is activated or not.
> If the watchdog functionality is not activated then the watchdog interface
> can be not registered and eliminate unnecessary pings and hence lower the
> power consumption by avoiding waking up the device.
> The feature can be deactivated also without reboot
> in that case the watchdog device should be unregistered at runtime.
> 
> Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> ---
> V2: rework unregistration
> V3: rebase; implement unregistraion also at runtime
> V4: Rebase the code over patchset : "watchdog: Replace driver based refcounting"
> 
>  drivers/watchdog/mei_wdt.c | 196 ++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 187 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/watchdog/mei_wdt.c b/drivers/watchdog/mei_wdt.c
> index e7e3f144f2b0..85b27fc5d4ec 100644
> --- a/drivers/watchdog/mei_wdt.c
> +++ b/drivers/watchdog/mei_wdt.c
>  
[ ... ]

> +static void mei_wdt_unregister_work(struct work_struct *work)
> +{
> +	struct mei_wdt *wdt = container_of(work, struct mei_wdt, unregister);
> +
> +	mei_wdt_unregister(wdt);
> +}

Registration is synchronous, unregistration is asynchronous.

Assuming that is on purpose, I think it warrants an explanation.

Thanks,
Guenter