linux-kernel - Re: [PATCH] RFC, watchdog: add generic wdt driver API

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Message-ID: <20111204125928.GB5788@pengutronix.de>
Date:	Sun, 4 Dec 2011 13:59:28 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Heiko Schocher <hs@...x.de>
Cc:	linux-watchdog@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Wolfgang Denk <wd@...x.de>, Stefan Roese <sr@...x.de>
Subject: Re: [PATCH] RFC, watchdog: add generic wdt driver API

On Sun, Dec 04, 2011 at 10:53:43AM +0100, Heiko Schocher wrote:
> This driver implements a character device with major number 10 and minor
> number 130.  It is a software abstraction of the hardware watchdog
> with two different APIs.  While the driver periodically triggers the
> hardware watchdog, the software can setup independent timeout periods.
> 
> "REGULAR API"
> provides a facility to setup a watchdog behaviour shared by all
> processes using the driver.  This interface uses read, write and
> ioctl calls.
> 
> "CHAIN API"
> can be used to register configurable "watchdog chains" from
> kernel and/or user space. This interface uses ioctl calls only.
> 
> more info about this two APIs are found in
> Documentation/watchdog/wd-api.txt
> 
> Different hardware layers can attached to this driver. As this
> is an RFC add in this patch also, as an example for an hardware
> layer, support for the arm davinci internal WDT.
> 
> Signed-off-by: Heiko Schocher <hs@...x.de>
> Cc: linux-watchdog@...r.kernel.org
> Cc: devicetree-discuss@...ts.ozlabs.org
> Cc: linux-kernel@...r.kernel.org
> Cc: Wolfgang Denk <wd@...x.de>
> Cc: Stefan Roese <sr@...x.de>
> 
> ---
> This patch is a port from Linux 2.4 and thought as an RFC, so comments
> are greately appreciated. First question is, has this watchdog driver
> API a chance to go in mainline? If so, what is the direction to
> go to push it ...

I don't see this flying. We finally have a watchdog framework in the kernel
which covers the long existing API used by existing drivers. If I understood it
right, this additional API needs new drivers for all the watchdogs? Also, I
didn't fully get what you are missing from the combination of the current API
and additional userspace-handling? (check [1] for one example, not really
covering your use case but showing a potential way maybe) Didn't look much at
the code, but glimpsing says it needs some cleanups regarding comments and
excessive debug output.

Regards,

   Wolfram

[1] http://lists.freedesktop.org/archives/systemd-devel/2011-November/003802.html

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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