linux-kernel - [PATCH] pwm-backlight: fix bogus request for GPIO#0 when instantiated from DT

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Date:	Wed, 20 Aug 2014 08:38:36 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Bryan Wu <cooloney@...il.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Lee Jones <lee.jones@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org
Cc:	Lothar Waßmann <LW@...O-electronics.de>
Subject: [PATCH] pwm-backlight: fix bogus request for GPIO#0 when instantiated from DT

commit 257462dbf3ed ("pwm-backlight: switch to gpiod interface")
introduced a regression leading to acquiring a bogus GPIO-0 when
configured from DT without an 'enable-gpios' property.
The driver will happily accept the 0 initialized 'enable_gpio' member
of the struct platform_pwm_backlight_data as valid gpio number, and
request this GPIO as enable pin. In case of multiple driver instances,
the second will fail to register with the error message:
pwm-backlight backlight1.23: failed to request GPIO#0: -16

Fix this by setting enable_gpio in the pdata struct to -EINVAL.

Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
---
 drivers/video/backlight/pwm_bl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index d7a3d13..e6ef6b4 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -172,7 +172,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
 		data->dft_brightness = value;
 		data->max_brightness--;
 	}
-
+	data->enable_gpio = -EINVAL;
 	return 0;
 }
 
-- 
1.7.10.4

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