Re: [Watchdog drivers] - WDIOC_GETSUPPORT clarification

[Hans de Goede <hdegoede@redhat.com>]

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.

Regards,

Hans