linux-kernel - Re: [PATCH] leds: pm8058: Make ledtype pointer sized type

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Message-ID: <20171130223406.GC2808@amd>
Date:   Thu, 30 Nov 2017 23:34:07 +0100
From:   Pavel Machek <pavel@....cz>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Richard Purdie <rpurdie@...ys.net>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH] leds: pm8058: Make ledtype pointer sized type

On Thu 2017-11-30 22:58:55, Jacek Anaszewski wrote:
> On 11/30/2017 10:40 AM, Pavel Machek wrote:
> > On Wed 2017-11-29 19:05:43, Bjorn Andersson wrote:
> >> The pointer returned by of_device_get_match_data() doesn't have the same
> >> size as u32 on 64-bit architectures, causing issues when compile testing
> >> the driver on such platform. Make ledtype unsigned long instead, to
> >> solve this problem.
> >>
> >> Fixes: 7f866986e705 ("leds: add PM8058 LEDs driver")
> >> Cc: Linus Walleij <linus.walleij@...aro.org>
> >> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > 
> > Ummm... no?
> > 
> > extern const void *of_device_get_match_data(const struct device *dev);
> > 
> > 
> >> diff --git a/drivers/leds/leds-pm8058.c b/drivers/leds/leds-pm8058.c
> >> index a52674327857..cc2afe81720d 100644
> >> --- a/drivers/leds/leds-pm8058.c
> >> +++ b/drivers/leds/leds-pm8058.c
> >> @@ -29,7 +29,7 @@
> >>  struct pm8058_led {
> >>  	struct regmap *map;
> >>  	u32 reg;
> >> -	u32 ledtype;
> >> +	unsigned long ledtype;
> > 
> > Make it void *. u32 is buggy. unsigned long is merely ugly code. void
> > * is not nice, but certainly better than unsigned long.
> 
> unsigned long is correct, see below:
> 
> static const struct of_device_id pm8058_leds_id_table[] = {
>         {
>                 .compatible = "qcom,pm8058-led",
>                 .data = (void *)PM8058_LED_TYPE_COMMON
>         },
>         {
>                 .compatible = "qcom,pm8058-keypad-led",
>                 .data = (void *)PM8058_LED_TYPE_KEYPAD
>         },
>         {
>                 .compatible = "qcom,pm8058-flash-led",
>                 .data = (void *)PM8058_LED_TYPE_FLASH
>         },
>         { },
> };
> 
> of_device_get_match_data will return PM8058_LED_TYPE_*
> which clearly is a led type identifier.
> 
> Thus unsigned long looks reasonable.

Hmm. Ok. So u32 would actually make even more sense there (because
PM8058_LED_TYPE_* does not really need to be 64-bit), but it would
cause a warning.

I don't like this. This fix actually makes code waste memory and is
uglier.

...but we get a warning fix. So I don't like the patch, but it is an
improvement...

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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