Re: [Watchdog drivers] - WDIOC_GETSUPPORT clarification

[Guenter Roeck <linux@roeck-us.net>]

On 8/18/21 7:49 AM, Hans de Goede wrote:
> Hi,
> 
> On 8/18/21 4:13 PM, Guenter Roeck wrote:
>> On 8/18/21 2:57 AM, Jose Noguera wrote:
>>> Hello all!
>>>
>>> I’m Jose, working in Red Hat on Fedora IoT and RHEL For Edge related projects.
>>>
>>> While trying to add the feature of figuring out whether the current boot was triggered or not by a hardware watchdog using wdctl, we’ve found an odd behaviour in the drivers definition that we would like to check with you.
>>>
>>> Looking specifically for the flag WDIOF_CARDRESET, we can find 40 files that contain it:
>>>
>>> $ grep -rl CARDRESET drivers/watchdog/ | wc -l
>>> 40
>>>
>>> but only 19 of them have the flag advertised in the options field of the watchdog_info struct returned by the WDIOC_GETSUPPORT ioctl.
>>>
>>> This leads to wdctl not showing WDIOF_CARDRESET for drivers like i6300esb, even when the board had been reset this way:
>>>
>>> $ sudo wdctl
>>> Device: /dev/watchdog0
>>> Identity: i6300ESB timer [version 0]
>>> Timeout: 30 seconds
>>> Pre-timeout: 0 seconds
>>>
>>> FLAG DESCRIPTION STATUS BOOT-STATUS
>>> KEEPALIVEPING Keep alive ping reply 1 0
>>> MAGICCLOSE Supports magic close char 0 0
>>> SETTIMEOUT Set timeout (in seconds) 0 0
>>>
>>> Working with Hans (in CC), we added a little patch (BugZilla ticket: 1993983) on wdctl and this would be the output of the command when it was a card reset triggered boot:
>>>
>>> $ sudo wdctl
>>> Device: /dev/watchdog0
>>> Identity: i6300ESB timer [version 0]
>>> Thank you all for your time,
>>>
>>> Jose
>>
>>> Timeout: 30 seconds
>>> Pre-timeout: 0 seconds
>>>
>>> FLAG DESCRIPTION STATUS BOOT-STATUS
>>> CARDRESET Card previously reset the CPU 1 1
>>> KEEPALIVEPING Keep alive ping reply 1 0
>>> MAGICCLOSE Supports magic close char 0 0
>>> SETTIMEOUT Set timeout (in seconds) 0 0
>>>
>>> So our question is, may we know what is intended to be present in ident.options? What should the API call WDIOC_GETSUPPORT return in the options field?
>>>
>>
>> Search for WDIOC_GETSUPPORT in Documentation/watchdog/watchdog-api.rst.
>> I don't see any ambiguity there. Patches welcome.
> 
> Ok, so drivers which may set CARDRESET in their GETBOOTSTATUS reply, but
> don't advertise this in their GETSUPPORT watchdog_info.options reply
> are buggy and should be fixed, got it. Thanks.
> 
> I've made a note about fixing this in a possible-kernel-projects document
> which I keep for when people who are interested in kernel development
> ask me for projects.
> 

With an add-on: If the driver in question is an old-style driver, anyone
affected by the problem should really convert the driver to support
the watchdog subsystem.

Thanks,
Guenter

> Regards,
> 
> Hans
>