Re: [Watchdog drivers] - WDIOC_GETSUPPORT clarification

[Peter Robinson <perobins@redhat.com>]

On Wed, 2021-08-18 at 07:53 -0700, Guenter Roeck wrote:
> 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.

Would you have a link to any docs/posts outlining what needs to be done
for conversion to the watchdog subsystem?

Regards,
Peter