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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Matt Ranostay <matt.ranostay@konsulko.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 003/228] tsl2550: fix lux1_input error in low light
Date:   Tue,  2 Oct 2018 06:21:40 -0700
Message-Id: <20181002132459.260658259@linuxfoundation.org>
In-Reply-To: <20181002132459.032960735@linuxfoundation.org>
References: <20181002132459.032960735@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Ranostay <matt.ranostay@konsulko.com>

[ Upstream commit ce054546cc2c26891cefa2f284d90d93b52205de ]

ADC channel 0 photodiode detects both infrared + visible light,
but ADC channel 1 just detects infrared. However, the latter is a bit
more sensitive in that range so complete darkness or low light causes
a error condition in which the chan0 - chan1 is negative that
results in a -EAGAIN.

This patch changes the resulting lux1_input sysfs attribute message from
"Resource temporarily unavailable" to a user-grokable lux value of 0.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/misc/tsl2550.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/misc/tsl2550.c
+++ b/drivers/misc/tsl2550.c
@@ -177,7 +177,7 @@ static int tsl2550_calculate_lux(u8 ch0,
 		} else
 			lux = 0;
 	else
-		return -EAGAIN;
+		return 0;
 
 	/* LUX range check */
 	return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux;