Re: [PATCH 1/5] watchdog: Create watchdog device in watchdog_dev.c

[Guenter Roeck]

On 12/22/2015 07:33 AM, Damien Riegel wrote:
> On Mon, Dec 21, 2015 at 03:28:39PM -0800, Guenter Roeck wrote:
> > On 12/21/2015 09:31 AM, Damien Riegel wrote:
> > > On Sun, Dec 20, 2015 at 01:04:59PM -0800, Guenter Roeck wrote:
> > > > The watchdog character device is currently created in watchdog_dev.c,
> > > > and the watchdog device in watchdog_core.c. This results in
> > > > cross-dependencies, since device creation needs to know the watchdog
> > > > character device number as well as the watchdog class, both of which
> > > > reside in watchdog_dev.c.
> > > >
> > > > Create the watchdog device in watchdog_dev.c to simplify the code.
> > > >
> > > > Inspired by earlier patch set from Damien Riegel.
> > >
> > > Hi Guenter,
> > >
> > > The main purpose of my patch was to inverse the device creation and the
> > > cdev registration to avoid a racy situation, bu you have dropped that in
> > > this version. Is there a reason for that?
> > Every other driver I looked at does it in the same order (cdev first, device
> > second). I don't really know if doing it differently has any undesired
> > side effect, so I wanted to play safe.
> >
> > It would help a lot if someone listening to this exchange can confirm
> > that it is ok to create the device first, followed by the character device.
>
> The issue is that some drivers use watchdog_device->dev in their
> watchdog_ops functions. With a quick grep, I could spot 3 examples:
>
>   - bcm2835_wdt_stop in bcm2835_wdt.c
>   - gpio_wdt_hwping in gpio_wdt.c
>   - a21_wdt_set_timeout in mena21_wdt.c
>
> Maybe we should simply fix these drivers and keep watchdog_device->dev
> for core internal usage?

Yes, I have been thinking about that - essentially move the ->dev pointer
to the internal data structure and either use pr_ functions in those drivers,
or save a pointer to the platform device (if available) and use it.

I think I'll start working on a follow-up patch set to do just that.

Guenter

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