David Hendricks (dhendrix@chromium.org) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/14143 -gerrit commit c499cad619bfdc7e0b9dc1bacef23b83f5132f38 Author: David Hendricks <dhendrix@chromium.org> Date: Fri Mar 18 20:23:05 2016 -0700 gpio: Add support for extended binary number system This adds yet another number system. In it, binary representation is extended to allow floating/high-Z values to count in the result. A 'Z' value at position N will yield a value of 0 at position N and a value of 1 at position (1 << N << num_gpio). For example: 000Z => 0b1_0000 100Z => 0b1_1000 The advantage is that the value is simple to compute and translate to/from hex. The drawback is that the number space is not contiguous. BRANCH=none BUG=none TEST=stubbed out and tested for a 3-wide raw value, see comments in gerrit for the full table. Change-Id: I121e0cac9fa84fcbb261d1d84dcb20cfd49e5518 Signed-off-by: David Hendricks <dhendrix@chromium.org> --- src/include/gpio.h | 13 +++++++++++++ src/lib/gpio.c | 18 ++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/src/include/gpio.h b/src/include/gpio.h index 4627e44..0acd5b0 100644 --- a/src/include/gpio.h +++ b/src/include/gpio.h @@ -42,6 +42,19 @@ int gpio_base2_value(gpio_t gpio[], int num_gpio); /* * Read the value presented by the set of GPIOs, when each pin is interpreted + * as a base-2 digit (LOW = 0, HIGH = 1). If a pin is in its Z/floating state + * the value becomes (1 << pin_num << num_gpio). + * + * Caveat: This scheme makes the number space discontinuous. The advantage is + * that it's simple to compute and translate to/from hex. + * + * gpio[]: pin positions to read. gpio[0] is less significant than gpio[1]. + * num_gpio: number of pins to read. + */ +int gpio_base2_ext_value(gpio_t gpio[], int num_gpio); + +/* + * Read the value presented by the set of GPIOs, when each pin is interpreted * as a base-3 digit (LOW = 0, HIGH = 1, Z/floating = 2). * Example: X1 = Z, X2 = 1 -> gpio_base3_value({GPIO(X1), GPIO(X2)}) = 5 * BASE3() from <base3.h> can generate numbers to compare the result to. diff --git a/src/lib/gpio.c b/src/lib/gpio.c index 2e34595..78a383a 100644 --- a/src/lib/gpio.c +++ b/src/lib/gpio.c @@ -35,6 +35,24 @@ int gpio_base2_value(gpio_t gpio[], int num_gpio) return result; } +int gpio_base2_ext_value(gpio_t gpio[], int num_gpio) +{ + int temp, index, result = 0; + + for (index = num_gpio - 1; index >= 0; --index) { + temp = gpio_get(gpio[index]); + printk(BIOS_DEBUG, "%c ", temp == Z ? 'Z' : temp + 0x30); + + if (temp == Z) + result += (1 << index << num_gpio); + else + result += temp * (1 << index); + } + + printk(BIOS_DEBUG, "= 0x%x (extended binary number system)\n", result); + return result; +} + int _gpio_base3_value(gpio_t gpio[], int num_gpio, int binary_first) { /*