From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michele De Candia (VT)" Subject: [PATCH] TSL2550 driver bugfix Date: Tue, 30 Jun 2009 17:31:08 +0200 Message-ID: <4A4A2FBC.1060804@valueteam.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------000109070601090503020902" Return-path: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: giometti-k2GhghHVRtY@public.gmane.org List-Id: linux-i2c@vger.kernel.org This is a multi-part message in MIME format. --------------000109070601090503020902 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi all, I've tested TSL2550 driver and I've found a bug: when light is off, returned value from tsl2550_calculate_lux function is -1 when it should be 0 (sensor correctly read that light was off). I think the bug is that a zero c0 value (approximated value of ch0) is misinterpreted as an error. I'm attaching you a patch that fixes the bug. Regards, Michele Jr De Candia --------------000109070601090503020902 Content-Type: text/x-patch; name="tsl2550_nolight_bugfix.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="tsl2550_nolight_bugfix.patch" Signed-off-by: Michele Jr De Candia diff --git a/drivers/i2c/chips/tsl2550.c b/drivers/i2c/chips/tsl2550.c index 1a9cc13..6bad072 100644 --- a/drivers/i2c/chips/tsl2550.c +++ b/drivers/i2c/chips/tsl2550.c @@ -189,10 +189,16 @@ static int tsl2550_calculate_lux(u8 ch0, u8 ch1) u8 r = 128; /* Avoid division by 0 and count 1 cannot be greater than count 0 */ - if (c0 && (c1 <= c0)) - r = c1 * 128 / c0; - else - return -1; + if (c0) { + if (c1 <= c0) + r = c1 * 128 / c0; + else + return -1; + + /* Calculate LUX */ + lux = ((c0 - c1) * ratio_lut[r]) / 256; + } + else lux = 0; /* Calculate LUX */ lux = ((c0 - c1) * ratio_lut[r]) / 256; --------------000109070601090503020902--