Re: [PATCH v4 1/3] leds: Require valid fwnode pointer for composing name

[Jacek Anaszewski]

Hi Alexander,

On 9/15/20 11:14 AM, Alexander Dahl wrote:
> Hello Jacek,
>
> thanks for your feedback. See below.
>
> Am Freitag, 11. September 2020, 23:26:43 CEST schrieb Jacek Anaszewski:
> > On 9/11/20 5:40 PM, Alexander Dahl wrote:
> > > The function 'led_compose_name()' is called in
> > > 'led_classdev_register_ext(()' only and in its implementation it always
> > > parses the fwnode passed with the init_data struct.  If there's no
> > > fwnode, EINVAL is returned and 'led_classdev_register_ext()' returns
> > > early.
> > >
> > > If this is detected early the same fallback mechanism can be used , as
> > > if init_data itself is NULL.  This will allow drivers to pass fully
> > > populated 'init_data' or sparse initialized 'init_data' with a NULL
> > > fwnode in a more elegant way with only one function call.
> > >
> > > Fixes: bb4e9af0348d ("leds: core: Add support for composing LED class
> > > device names") Suggested-by: Pavel Machek <pavel@xxxxxx>
> > > Signed-off-by: Alexander Dahl <post@xxxxxxxxxxx>
> > > ---
> > >
> > > Notes:
> > >       v4:
> > >         * added this patch to series (Suggested-by: Pavel Machek)
> > >    
> > >    drivers/leds/led-class.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> > > index cc3929f858b6..3da50c7ecfe7 100644
> > > --- a/drivers/leds/led-class.c
> > > +++ b/drivers/leds/led-class.c
> > > @@ -346,7 +346,7 @@ int led_classdev_register_ext(struct device *parent,
> > >
> > >    	const char *proposed_name = composed_name;
> > >    	int ret;
> > >
> > > -	if (init_data) {
> > > +	if (init_data && init_data->fwnode) {
> >
> > This does not cover the case when we don't have fwnode but we
> > have init_data->default_label that led_compose_name() can make use of.
> >
> > >    		if (init_data->devname_mandatory && !init_data->devicename) {
> > >    		
> > >    			dev_err(parent, "Mandatory device name is missing");
> > >    			return -EINVAL;
>
> You're right, I missed that part in that if/else if construct in
> led_compose_name() … I looked at the code for some more time now and could not
> come up with an elegant change to the led-core or led-class. :-/
>
> However I also had another look at leds-pwm and for me it seems that it is
> used by fwnode (DT, ACPI, ??) based devices only.  I could not find a single
> user of leds-pwm as a platform driver, which is probably why 141f15c66d94
> ("leds: pwm: remove header") was possible?

In fact it looks like that patch was pointless, since it precluded the
use of struct led_pwm_platform_data anywhere besides the leds-pwm
driver.

> I had a look at the history of the leds-pwm driver and when introduced in 2009
> platform based board files where a thing, no dt, of, or fwnode yet, at least
> for arm, right?  Device tree support for leds-pwm was added in 2012 by Peter
> Ujfalusi.
>
> So if those code paths in leds-pwm are not used anymore, what about dropping
> that platform support in leds-pwm driver?  That would mean we always have
> fwnode non-null and would not require a change in led-class at all?

git grep led_pwm_platform_data in fact shows only references in
leds-pwm.c, so yes, I think the platform support seems to be redundant.

--
Best regards,
Jacek Anaszewski