linux-kernel - Re: 回复： [PATCH] watchdog: sbsa-gwdt: clamp timeout before updating wdd->timeout

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Message-ID: <39f2a3ac-6906-4970-822e-d1f5cdced563@roeck-us.net>
Date: Fri, 19 Dec 2025 07:41:07 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: 1536943441 <1536943441@...com>,
 linux-watchdog <linux-watchdog@...r.kernel.org>
Cc: wim <wim@...ux-watchdog.org>, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: 回复： [PATCH] watchdog: sbsa-gwdt: clamp timeout before updating wdd->timeout

On 12/19/25 01:46, 1536943441 wrote:
> Hi Guenter,
> 
> thank you for the detailed explanation.
> 
> I misunderstood the watchdog core semantics here. With max_hw_heartbeat_ms set, the userspace timeout can represent a virtual timeout and is not expected to be limited by the single hardware timeout. Given that, my change is indeed wrong
> and I will drop this patch.
> 
> One follow-up question: in my testing, "/sys/class/watchdog/watchdog0/max_timeout" always shows 0 for sbsa-gwdt.  Should the driver set wdd->max_timeout in probe(), or is a 0 value expected when max_hw_heartbeat_ms/virtual timeouts are used?
> 

The value is as expected, and the driver should not do anything. A value of 0
means "unlimited", which in practice means that the limit is UINT_MAX / 1000.

Turns out the attribute is not documented. We should add it to the ABI
documentation. If/when I find the time ...

Thanks,
Guenter