On 8/20/19 5:12 AM, Corey Minyard wrote:
On Mon, Aug 19, 2019 at 07:09:46PM -0600, Jerry Hoemann wrote:
On Mon, Aug 19, 2019 at 07:23:09PM -0500, Corey Minyard wrote:
On Mon, Aug 19, 2019 at 03:43:45PM -0700, Guenter Roeck wrote:
On Mon, Aug 19, 2019 at 03:37:01PM -0500, minyard@xxxxxxx wrote:
From: Corey Minyard <cminyard@xxxxxxxxxx>
This is for the read data pretimeout governor.
Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
On further thought, I think it would be a bad idea to add this
functionality: It changes the userspace ABI for accessing the watchdog
device. Today, when a watchdog device is opened, it does not provide
read data, it does not hang, and returns immediately. A "cat" from it
is an easy and quick means to test if a watchdog works.
Umm, why would a "cat" from a watchdog tell you if a watchdog works?
cat /dev/watchdog starts the watchdog running.
Then one can do useful things like monitor /sys/class/watchdog/watchdogN and see
time ticking down, etc..,
echo V > /dev/watchdog stops the watchdog assuming driver supports WDIOF_MAGICCLOSE.
So I can test without having to reboot.
One can't test magic close with the proposed change as /dev/watchdog
is exclusive open.
Sure you can:
# echo "" >/dev/watchdog0
[ 92.390649] watchdog: watchdog0: watchdog did not stop!
# sleep 2
# cat /sys/class/watchdog/watchdog0/timeleft
8
# echo "V" >/dev/watchdog0
Works just fine. But I can make it so that reading returns an error
unless the governor is the read one.
The question is if this is required to transfer the IPMI watchdog
over to the standard interface. It currently has this function,
do we do an API change to move it over?
Having to change the standard watchdog API to accommodate a non-standard driver
is most definitely not the right approach. If it was, anyone could use it to
force standard API/ABI changes. Just implement driver X outside its subsystem
and then claim you need to change the subsystem to accommodate it.
On a side note, a standard watchdog driver can implement its own ioctl functions.
Guenter
-corey
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Jerry Hoemann Software Engineer Hewlett Packard Enterprise
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