Re: [RFC PATCH] watchdog: HACK: disable bind attributes with NOWAYOUT

[Wolfram Sang]

> void watchdog_set_nowayout(struct watchdog_device *wdd, struct driver
>  *drv, bool nowayout)
> 
> I'd think this would work from a layering perspective.

No, this is also bogus. probe() works per device, and
.suppress_bind_attrs works per driver. We need to tackle this in the
init callback.



signature.asc
Description: PGP signature

Re: [RFC PATCH] watchdog: HACK: disable bind attributes with NOWAYOUT

[Wolfram Sang]

Hi Guenter,

> > -   if (nowayout)
> > +   if (nowayout) {
> > set_bit(WDOG_NO_WAY_OUT, >status);
> > +   wdd->parent->driver->suppress_bind_attrs = true;
> 
> That makes sense to me. We can not assume that wdd->parent is set, so it 
> won't work as-is.

Good point!

> Not sure what a "correct" solution might be. Passing "parent" as argument 
> doesn't really
> solve any layering argument

I totally agree. I opted for passing a pointer to the driver to modify:

void watchdog_set_nowayout(struct watchdog_device *wdd, struct driver
   *drv, bool nowayout)

I'd think this would work from a layering perspective.

> Did you ensure that the attributes are not already created by the time
> suppress_bind_attrs is set ?

Not yet. I first wanted to make sure if it makes sense, at all. But will
do for later versions.

Thanks for the review,

   Wolfram



signature.asc
Description: PGP signature

Re: [RFC PATCH] watchdog: HACK: disable bind attributes with NOWAYOUT

[Guenter Roeck]

On 08/28/2018 03:29 AM, Wolfram Sang wrote:

With NOWAYOUT, prevent bind/unbind possibilities in SYSFS.
Proof-of-concept, not for upstream yet.

Signed-off-by: Wolfram Sang 
---

So, this is really an RFC to check if something like this is considered useful
or not. If so, we probably need to do it differently because modifying the
parent's driver is likely a layering violation. We could add the driver to
modify as an optional parameter to watchdog_set_nowayout(). I wouldn't favor
another seperate function to configure this, but am open for discussion.

Thanks,

Wolfram

  include/linux/watchdog.h | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 44985c4a1e86..241de0fa0010 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -143,8 +143,10 @@ static inline bool watchdog_hw_running(struct 
watchdog_device *wdd)
  /* Use the following function to set the nowayout feature */
  static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool 
nowayout)
  {
-   if (nowayout)
+   if (nowayout) {
set_bit(WDOG_NO_WAY_OUT, >status);
+   wdd->parent->driver->suppress_bind_attrs = true;


That makes sense to me. We can not assume that wdd->parent is set, so it won't 
work as-is.
Not sure what a "correct" solution might be. Passing "parent" as argument 
doesn't really
solve any layering argument - stating that it violates layering if parent is 
pulled from
wdd but not if it is passed as argument seems to be a bit ridiculous.

Did you ensure that the attributes are not already created by the time
suppress_bind_attrs is set ?

Thanks,
Guenter

[RFC PATCH] watchdog: HACK: disable bind attributes with NOWAYOUT

[Wolfram Sang]

With NOWAYOUT, prevent bind/unbind possibilities in SYSFS.
Proof-of-concept, not for upstream yet.

Signed-off-by: Wolfram Sang 
---

So, this is really an RFC to check if something like this is considered useful
or not. If so, we probably need to do it differently because modifying the
parent's driver is likely a layering violation. We could add the driver to
modify as an optional parameter to watchdog_set_nowayout(). I wouldn't favor
another seperate function to configure this, but am open for discussion.

Thanks,

   Wolfram

 include/linux/watchdog.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index 44985c4a1e86..241de0fa0010 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -143,8 +143,10 @@ static inline bool watchdog_hw_running(struct 
watchdog_device *wdd)
 /* Use the following function to set the nowayout feature */
 static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool 
nowayout)
 {
-   if (nowayout)
+   if (nowayout) {
set_bit(WDOG_NO_WAY_OUT, >status);
+   wdd->parent->driver->suppress_bind_attrs = true;
+   }
 }
 
 /* Use the following function to stop the watchdog on reboot */
-- 
2.11.0