Re: [PATCH 1/3] watchdog: Select CONFIG_PARAMETER

[Christian Eggers <ceggers@arri.de>]

Hi Sascha,

Am Mittwoch, 22. Januar 2020, 09:21:15 CET schrieb Sascha Hauer:
> Hi Christian,
> 
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index 45dd41a2a..34b7fea39 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -4,6 +4,7 @@ config WATCHDOG_IMX_RESET_SOURCE
> > 
> >  menuconfig WATCHDOG
> >  
> >  	bool "Watchdog support"
> > 
> > +	select PARAMETER
> 
> I think this goes into the wrong direction. With CONFIG_PARAMETER
> enabled we get support for adjusting device parameters from the shell.
> In environments without shell support parameter support is not needed.
> For example the watchdog C API doesn't need parameter support and is
> still usable.
> 
> The static inline wrappers for dev_add_param_* should return NULL
> instead of returning ERR_PTR(-ENOSYS).

initially I came to the same result. But previous commits to param.h went in 
the opposite direction:

> 03b59bdb64 ("paramter: The dev_add_param_*() return ERR_PTR(), change
> no-ops") to return ERR_PTR(-ENOSYS) instead of NULL
> 
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

and

> c5d95eb4c7 ("param: make parameter functions more consistent")
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Most of the callers of dev_add_param*()  don't care about the returned param 
pointer at all. Some are checking against PTR_ERR() which would not be hit if 
returning NULL (this is what we want).

A few callers have to changed if a NULL pointer can be returned:
- __nvvar_add()
- state_string_create()  stores the result in state_string::param, but seems 
to be used nowhere
- mci_register() dito for mci::param_probe
- state_uint8_create() dito for state_uint32::param
- state_uint32_create() dito

For me it looks reasonable to return a NULL pointer if CONFIG_PARAMETER is not 
set (as you suggested). Only __nvvar_add() needs slight changes and I would 
remove needless storage of param in structs state_string, mci and 
state_uint32.

Shall I start?

regards
Christian



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