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[92.34.201.90]) by smtp.gmail.com with ESMTPSA id g25sm2954871ljn.107.2020.02.08.04.34.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Feb 2020 04:34:03 -0800 (PST) From: Linus Walleij To: Jonathan Cameron , linux-iio@vger.kernel.org Cc: Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-input@vger.kernel.org, Linus Walleij , Jonathan Bakker Subject: [PATCH] RFT: iio: gp2ap002: Replace LUT with math Date: Sat, 8 Feb 2020 13:33:59 +0100 Message-Id: <20200208123359.396-1-linus.walleij@linaro.org> X-Mailer: git-send-email 2.21.1 MIME-Version: 1.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org This replaces the current-to-lux look up table with some integer math using int_pow() from . Drop the unused in the process. Cc: Jonathan Bakker Signed-off-by: Linus Walleij --- I would appreciate testing that this give the right result. Using math does look a lot better. --- drivers/iio/light/gp2ap002.c | 94 +++--------------------------------- 1 file changed, 7 insertions(+), 87 deletions(-) diff --git a/drivers/iio/light/gp2ap002.c b/drivers/iio/light/gp2ap002.c index 433907619268..153ae0a163ab 100644 --- a/drivers/iio/light/gp2ap002.c +++ b/drivers/iio/light/gp2ap002.c @@ -33,7 +33,6 @@ #include #include #include -#include #include #define GP2AP002_PROX_CHANNEL 0 @@ -205,71 +204,10 @@ static irqreturn_t gp2ap002_prox_irq(int irq, void *d) return IRQ_HANDLED; } -struct gp2ap002_illuminance { - unsigned int curr; - unsigned int lux; -}; - -/* - * This array maps current and lux. - * - * Ambient light sensing range is 3 to 55000 lux. - * - * This mapping is based on the following formula. - * illuminance = 10 ^ (current / 10) - */ -static const struct gp2ap002_illuminance gp2ap002_illuminance_table[] = { - { .curr = 5, .lux = 3 }, - { .curr = 6, .lux = 4 }, - { .curr = 7, .lux = 5 }, - { .curr = 8, .lux = 6 }, - { .curr = 9, .lux = 8 }, - { .curr = 10, .lux = 10 }, - { .curr = 11, .lux = 12 }, - { .curr = 12, .lux = 16 }, - { .curr = 13, .lux = 20 }, - { .curr = 14, .lux = 25 }, - { .curr = 15, .lux = 32 }, - { .curr = 16, .lux = 40 }, - { .curr = 17, .lux = 50 }, - { .curr = 18, .lux = 63 }, - { .curr = 19, .lux = 79 }, - { .curr = 20, .lux = 100 }, - { .curr = 21, .lux = 126 }, - { .curr = 22, .lux = 158 }, - { .curr = 23, .lux = 200 }, - { .curr = 24, .lux = 251 }, - { .curr = 25, .lux = 316 }, - { .curr = 26, .lux = 398 }, - { .curr = 27, .lux = 501 }, - { .curr = 28, .lux = 631 }, - { .curr = 29, .lux = 794 }, - { .curr = 30, .lux = 1000 }, - { .curr = 31, .lux = 1259 }, - { .curr = 32, .lux = 1585 }, - { .curr = 33, .lux = 1995 }, - { .curr = 34, .lux = 2512 }, - { .curr = 35, .lux = 3162 }, - { .curr = 36, .lux = 3981 }, - { .curr = 37, .lux = 5012 }, - { .curr = 38, .lux = 6310 }, - { .curr = 39, .lux = 7943 }, - { .curr = 40, .lux = 10000 }, - { .curr = 41, .lux = 12589 }, - { .curr = 42, .lux = 15849 }, - { .curr = 43, .lux = 19953 }, - { .curr = 44, .lux = 25119 }, - { .curr = 45, .lux = 31623 }, - { .curr = 46, .lux = 39811 }, - { .curr = 47, .lux = 50119 }, -}; - static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002) { - const struct gp2ap002_illuminance *ill1; - const struct gp2ap002_illuminance *ill2; int ret, res; - int i; + u64 lux; ret = iio_read_channel_processed(gp2ap002->alsout, &res); if (ret < 0) @@ -277,31 +215,13 @@ static int gp2ap002_get_lux(struct gp2ap002 *gp2ap002) dev_dbg(gp2ap002->dev, "read %d mA from ADC\n", res); - ill1 = &gp2ap002_illuminance_table[0]; - if (res < ill1->curr) { - dev_dbg(gp2ap002->dev, "total darkness\n"); - return 0; - } - for (i = 0; i < ARRAY_SIZE(gp2ap002_illuminance_table) - 1; i++) { - ill1 = &gp2ap002_illuminance_table[i]; - ill2 = &gp2ap002_illuminance_table[i + 1]; - - if (res > ill2->curr) - continue; - if ((res <= ill1->curr) && (res >= ill2->curr)) - break; + lux = int_pow(10, (res/10)); + if (lux > INT_MAX) { + dev_err(gp2ap002->dev, "lux overflow, capped\n"); + lux = INT_MAX; } - if (res > ill2->curr) { - dev_info_once(gp2ap002->dev, "max current overflow\n"); - return ill2->curr; - } - /* Interpolate and return */ - dev_dbg(gp2ap002->dev, "interpolate index %d and %d\n", i, i + 1); - /* How many steps along the curve */ - i = res - ill1->curr; /* x - x0 */ - /* Linear interpolation */ - return ill1->lux + i * - ((ill2->lux - ill1->lux) / (ill2->curr - ill1->curr)); + + return (int)lux; } static int gp2ap002_read_raw(struct iio_dev *indio_dev,