From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Cameron Subject: Re: [PATCH] TSL2550 driver bugfix Date: Wed, 01 Jul 2009 16:06:23 +0000 Message-ID: <4A4B897F.30704@cam.ac.uk> References: <4A4A2FBC.1060804@valueteam.com> <4A4A4036.3000408@cam.ac.uk> <4A4B1A71.20101@valueteam.com> <4A4B33D8.1070903@cam.ac.uk> <4A4B7904.5010301@valueteam.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4A4B7904.5010301-EZxuzQJkuwwybS5Ee8rs3A@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Michele De Candia (VT)" Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, giometti-k2GhghHVRtY@public.gmane.org List-Id: linux-i2c@vger.kernel.org > What do you think about 'Bugfix for missing Lux returning in dark > environment' ? That covers the key point, so fine. > Jonathan Cameron wrote: >> Looks good to me. (perhaps a bit more detail in the commit >> message of the patch?) >> >> Acked-by: Jonathan Cameron >> >>> Jonathan Cameron wrote: >>> >>>> Michele De Candia (VT) wrote: >>>> >>>> >>>>> 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 >>>>> >>>> Sounds reasonable, but I think a stray line got away in your patch >>>> (see below) >>>> Not to mention, if the c1 <= c0 check is still valid, should you not >>>> also >>>> confirm that c1 == 0 as well? Perhaps reverse the ordering? >>>> >>> That's right. A new patch can be found in attachment. >>> >>>> if (c1 <= c0) >>>> if(c0) { >>>> r = c1* 128 / c0; >>>> lux = ((c0 - c1) * ratio_lut[r]) / 256; >>>> } else >>>> lux = 0; >>>> else >>>> return -1; >>>> >>>> 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; >>>> >>>> >>>> This last line should have been removed I think? >>>> /* Calculate LUX */ >>>> lux = ((c0 - c1) * ratio_lut[r]) / 256; >>>> >>>> --- >>>> Jonathan Cameron >>>> >>>> >>> Than >>> >> >> > >