diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/include/gpio.h | 36 | ||||
| -rw-r--r-- | src/lib/gpio.c | 49 |
2 files changed, 82 insertions, 3 deletions
diff --git a/src/include/gpio.h b/src/include/gpio.h index ea03a23231..4627e4412c 100644 --- a/src/include/gpio.h +++ b/src/include/gpio.h @@ -29,6 +29,7 @@ void gpio_input_pulldown(gpio_t gpio); void gpio_input_pullup(gpio_t gpio); void gpio_input(gpio_t gpio); void gpio_output(gpio_t gpio, int value); +int _gpio_base3_value(gpio_t gpio[], int num_gpio, int binary_first); /* * Read the value presented by the set of GPIOs, when each pin is interpreted @@ -48,6 +49,39 @@ int gpio_base2_value(gpio_t gpio[], int num_gpio); * gpio[]: pin positions to read. gpio[0] is less significant than gpio[1]. * num_gpio: number of pins to read. */ -int gpio_base3_value(gpio_t gpio[], int num_gpio); +static inline int gpio_base3_value(gpio_t gpio[], int num_gpio) +{ + return _gpio_base3_value(gpio, num_gpio, 0); +} + +/* + * 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) in a non-standard + * ternary number system where the first 2^n natural numbers are represented + * as they would be in a binary system (without any Z digits), and the following + * 3^n-2^n numbers use the remaining ternary representations in the normal + * ternary system order (skipping the values that were already used up). + * This is useful for boards which initially used a binary board ID and later + * decided to switch to tri-state after some revisions have already been built. + * Example: For num_gpio = 2 we get the following representation: + * + * Number X1 X0 + * 0 0 0 + * 1 0 1 + * 2 1 0 + * 3 1 1 // Start counting ternaries back at 0 after this + * 4 0 2 // Skipping 00 and 01 which are already used up + * 5 1 2 // Skipping 10 and 11 which are already used up + * 6 2 0 + * 7 2 1 + * 8 2 2 + * + * gpio[]: pin positions to read. gpio[0] is less significant than gpio[1]. + * num_gpio: number of pins to read. + */ +static inline int gpio_binary_first_base3_value(gpio_t gpio[], int num_gpio) +{ + return _gpio_base3_value(gpio, num_gpio, 1); +} #endif /* __SRC_INCLUDE_GPIO_H__ */ diff --git a/src/lib/gpio.c b/src/lib/gpio.c index 5147cfebac..2e345956f8 100644 --- a/src/lib/gpio.c +++ b/src/lib/gpio.c @@ -35,7 +35,7 @@ int gpio_base2_value(gpio_t gpio[], int num_gpio) return result; } -int gpio_base3_value(gpio_t gpio[], int num_gpio) +int _gpio_base3_value(gpio_t gpio[], int num_gpio, int binary_first) { /* * GPIOs which are tied to stronger external pull up or pull down @@ -50,6 +50,8 @@ int gpio_base3_value(gpio_t gpio[], int num_gpio) int temp; int index; int result = 0; + int has_z = 0; + int binary_below = 0; char value[32]; assert(num_gpio <= 32); @@ -85,8 +87,51 @@ int gpio_base3_value(gpio_t gpio[], int num_gpio) temp |= ((value[index] ^ temp) << 1); printk(BIOS_DEBUG, "%c ", tristate_char[temp]); result = (result * 3) + temp; + + /* + * For binary_first we keep track of the normal ternary result + * and whether we found any pin that was a Z. We also determine + * the amount of numbers that can be represented with only + * binary digits (no Z) whose value in the normal ternary system + * is lower than the one we are parsing. Counting from the left, + * we add 2^i for any '1' digit to account for the binary + * numbers whose values would be below it if all following + * digits we parsed would be '0'. As soon as we find a '2' digit + * we can total the remaining binary numbers below as 2^(i+1) + * because we know that all binary representations counting only + * this and following digits must have values below our number + * (since 1xxx is always smaller than 2xxx). + * + * Example: 1 0 2 1 (counting from the left / most significant) + * '1' at 3^3: Add 2^3 = 8 to account for binaries 0000-0111 + * '0' at 3^2: Ignore (not all binaries 1000-1100 are below us) + * '2' at 3^1: Add 2^(1+1) = 4 to account for binaries 1000-1011 + * Stop adding for lower digits (3^0), all already accounted + * now. We know that there can be no binary numbers 1020-102X. + */ + if (binary_first && !has_z) { + switch(temp) { + case 0: /* Ignore '0' digits. */ + break; + case 1: /* Account for binaries 0 to 2^index - 1. */ + binary_below += 1 << index; + break; + case 2: /* Account for binaries 0 to 2^(index+1) - 1. */ + binary_below += 1 << (index + 1); + has_z = 1; + } + } + } + + if (binary_first) { + if (has_z) + result = result + (1 << num_gpio) - binary_below; + else /* binary_below is normal binary system value if !has_z. */ + result = binary_below; } - printk(BIOS_DEBUG, "= %d\n", result); + + printk(BIOS_DEBUG, "= %d (%s base3 number system)\n", result, + binary_first ? "binary_first" : "standard"); /* Disable pull up / pull down to conserve power */ for (index = 0; index < num_gpio; ++index) |