[PATCH] leds: tca6507: fix error handling of using fwnode_property_read_string

[PATCH] leds: tca6507: fix error handling of using fwnode_property_read_string

[H. Nikolaus Schaller]

Commit 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")

changed to fwnode API but did not take into account that a missing property
"linux,default-trigger" now seems to return an error and as a side effect
sets value to -1. This seems to be different from of_get_property() which
always returned NULL in any case of error.

Neglecting this side-effect leads to

[   11.201965] Unable to handle kernel paging request at virtual address ffffffff when read

in the strcmp() of led_trigger_set_default() if there is no led-trigger
defined in the DTS.

I don't know if this was recently introduced somewhere in the fwnode lib
or if the effect was missed in initial testing. Anyways it seems to be a
bug to ignore the error return value of an optional value here in the
driver.

Fixes: 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
Cc: Marek Behún <kabel@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
---
 drivers/leds/leds-tca6507.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/leds-tca6507.c b/drivers/leds/leds-tca6507.c
index 07dd12686a696..634cabd5bb796 100644
--- a/drivers/leds/leds-tca6507.c
+++ b/drivers/leds/leds-tca6507.c
@@ -691,8 +691,9 @@ tca6507_led_dt_init(struct device *dev)
 		if (fwnode_property_read_string(child, "label", &led.name))
 			led.name = fwnode_get_name(child);
 
-		fwnode_property_read_string(child, "linux,default-trigger",
-					    &led.default_trigger);
+		if (fwnode_property_read_string(child, "linux,default-trigger",
+						&led.default_trigger))
+			led.default_trigger = NULL;
 
 		led.flags = 0;
 		if (fwnode_device_is_compatible(child, "gpio"))
-- 
2.38.1

Re: [PATCH] leds: tca6507: fix error handling of using fwnode_property_read_string

[Marek Behún]

On Sun,  2 Apr 2023 13:12:59 +0200
"H. Nikolaus Schaller" <hns@goldelico.com> wrote:

> Commit 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> 
> changed to fwnode API but did not take into account that a missing property
> "linux,default-trigger" now seems to return an error and as a side effect
> sets value to -1. This seems to be different from of_get_property() which
> always returned NULL in any case of error.
> 
> Neglecting this side-effect leads to
> 
> [   11.201965] Unable to handle kernel paging request at virtual address ffffffff when read
> 
> in the strcmp() of led_trigger_set_default() if there is no led-trigger
> defined in the DTS.
> 
> I don't know if this was recently introduced somewhere in the fwnode lib
> or if the effect was missed in initial testing. Anyways it seems to be a
> bug to ignore the error return value of an optional value here in the
> driver.
> 
> Fixes: 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> Cc: Marek Behún <kabel@kernel.org>
> Cc: NeilBrown <neilb@suse.de>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
> ---
>  drivers/leds/leds-tca6507.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/leds/leds-tca6507.c b/drivers/leds/leds-tca6507.c
> index 07dd12686a696..634cabd5bb796 100644
> --- a/drivers/leds/leds-tca6507.c
> +++ b/drivers/leds/leds-tca6507.c
> @@ -691,8 +691,9 @@ tca6507_led_dt_init(struct device *dev)
>  		if (fwnode_property_read_string(child, "label", &led.name))
>  			led.name = fwnode_get_name(child);
>  
> -		fwnode_property_read_string(child, "linux,default-trigger",
> -					    &led.default_trigger);
> +		if (fwnode_property_read_string(child, "linux,default-trigger",
> +						&led.default_trigger))
> +			led.default_trigger = NULL;
>  
>  		led.flags = 0;
>  		if (fwnode_device_is_compatible(child, "gpio"))

Reviewed-by: Marek Behún <kabel@kernel.org>

Re: [PATCH] leds: tca6507: fix error handling of using fwnode_property_read_string

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 1281 bytes --]

On Sun 2023-04-02 13:12:59, H. Nikolaus Schaller wrote:
> Commit 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> 
> changed to fwnode API but did not take into account that a missing property
> "linux,default-trigger" now seems to return an error and as a side effect
> sets value to -1. This seems to be different from of_get_property() which
> always returned NULL in any case of error.
> 
> Neglecting this side-effect leads to
> 
> [   11.201965] Unable to handle kernel paging request at virtual address ffffffff when read
> 
> in the strcmp() of led_trigger_set_default() if there is no led-trigger
> defined in the DTS.
> 
> I don't know if this was recently introduced somewhere in the fwnode lib
> or if the effect was missed in initial testing. Anyways it seems to be a
> bug to ignore the error return value of an optional value here in the
> driver.
> 
> Fixes: 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> Cc: Marek Behún <kabel@kernel.org>
> Cc: NeilBrown <neilb@suse.de>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>

Acked-by: Pavel Machek <pavel@ucw.cz>

BR,							Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

[-- Attachment #2: signature.asc --]
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Re: [PATCH] leds: tca6507: fix error handling of using fwnode_property_read_string

[Lee Jones]

On Sun, 02 Apr 2023, H. Nikolaus Schaller wrote:

> Commit 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
>
> changed to fwnode API but did not take into account that a missing property
> "linux,default-trigger" now seems to return an error and as a side effect
> sets value to -1. This seems to be different from of_get_property() which
> always returned NULL in any case of error.
>
> Neglecting this side-effect leads to
>
> [   11.201965] Unable to handle kernel paging request at virtual address ffffffff when read
>
> in the strcmp() of led_trigger_set_default() if there is no led-trigger
> defined in the DTS.
>
> I don't know if this was recently introduced somewhere in the fwnode lib
> or if the effect was missed in initial testing. Anyways it seems to be a
> bug to ignore the error return value of an optional value here in the
> driver.
>
> Fixes: 96f524105b9c ("leds: tca6507: use fwnode API instead of OF")
> Cc: Marek Behún <kabel@kernel.org>
> Cc: NeilBrown <neilb@suse.de>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
> ---
>  drivers/leds/leds-tca6507.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Applied, thanks

--
Lee Jones [李琼斯]