circuits_gpio

// SPDX-FileCopyrightText: 2023 Frank Hunleth, Connor Rigby
//
// SPDX-License-Identifier: Apache-2.0

#include "gpio_nif.h"

#include <string.h>

#include <stdint.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#include <sys/ioctl.h>
#include "linux/gpio.h"

#include "hal_cdev_gpio.h"

#define CONSUMER "circuits_gpio"

/* Some time between Linux 5.10 and Linux 5.15, GPIO numbering changed on
 * AM335x devices (Beaglebone, etc.). These devices have 4 banks of 32 GPIOs.
 * They used to be alphabetically sorted for file names which mirrored the
 * order they showed up in the I/O address map. Now they show up with the bank
 * at address 0x44c00000 coming after all of the 0x48000000 banks.
 *
 * To get the original mapping, gpiochips 0-3 need to be rotated.
 *
 * The real fix is to embrace cdev and stop using GPIO numbers, but that
 * requires changing a lot of code, so work around it.
 */
static int gpiochip_order_r[] = {15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0};

static void check_bbb_linux_5_15_gpio_change()
{
    // Check for the gpiochip ordering that has the 0x44c00000 controller
    // ordered AFTER the 0x48000000.
    //
    // These are ordered so that the for loop fails as soon as possible on
    // non-AM335x platforms. Since few devices get up to gpiochip3, the
    // readlink(2) call should fail and there shouldn't even be a string
    // compare.
    static const char *symlink_value[] = {
        "/sys/bus/gpio/devices/gpiochip3",
        "../../../devices/platform/ocp/44c00000.interconnect/44c00000.interconnect:segment@200000/44e07000.target-module/44e07000.gpio/gpiochip3",
        "/sys/bus/gpio/devices/gpiochip0",
        "../../../devices/platform/ocp/48000000.interconnect/48000000.interconnect:segment@0/4804c000.target-module/4804c000.gpio/gpiochip0",
        "/sys/bus/gpio/devices/gpiochip1",
        "../../../devices/platform/ocp/48000000.interconnect/48000000.interconnect:segment@100000/481ac000.target-module/481ac000.gpio/gpiochip1",
        "/sys/bus/gpio/devices/gpiochip2",
        "../../../devices/platform/ocp/48000000.interconnect/48000000.interconnect:segment@100000/481ae000.target-module/481ae000.gpio/gpiochip2"
    };

    char path[192];
    int i;

    for (i = 0; i < 8; i += 2) {
        ssize_t path_len = readlink(symlink_value[i], path, sizeof(path) - 1);
        if (path_len < 0)
            return;

        path[path_len] = '\0';
        if (strcmp(symlink_value[i + 1], path) != 0)
            return;
    }

    // This is a BBB with the new mapping. Rotate the scan order to compensate:
    gpiochip_order_r[15] = 3;
    gpiochip_order_r[14] = 0;
    gpiochip_order_r[13] = 1;
    gpiochip_order_r[12] = 2;
}

static int get_value_v2(int fd)
{
    struct gpio_v2_line_values vals;
    memset(&vals, 0, sizeof(vals));
    vals.mask = 1;

    if (ioctl(fd, GPIO_V2_LINE_GET_VALUES_IOCTL, &vals) < 0) {
        return -errno;
    }

    return vals.bits & 0x1;
}

static int set_value_v2(int fd, int value)
{
    struct gpio_v2_line_values vals;
    vals.bits = value;
    vals.mask = 1;

    if (ioctl(fd, GPIO_V2_LINE_SET_VALUES_IOCTL, &vals) < 0)
        return -errno;

    return 0;
}

static uint64_t config_to_flags(const struct gpio_pin *pin)
{
    uint64_t flags = pin->config.is_output ? GPIO_V2_LINE_FLAG_OUTPUT : GPIO_V2_LINE_FLAG_INPUT;

    switch (pin->config.pull) {
    case PULL_UP:
        flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_UP;
        break;
    case PULL_DOWN:
        flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN;
        break;
    case PULL_NONE:
        flags |= GPIO_V2_LINE_FLAG_BIAS_DISABLED;
        break;
    default:
        break;
    }

    switch (pin->config.trigger) {
    case TRIGGER_RISING:
        flags |= GPIO_V2_LINE_FLAG_EDGE_RISING;
        break;
    case TRIGGER_FALLING:
        flags |= GPIO_V2_LINE_FLAG_EDGE_FALLING;
        break;
    case TRIGGER_BOTH:
        flags |= GPIO_V2_LINE_FLAG_EDGE_RISING | GPIO_V2_LINE_FLAG_EDGE_FALLING;
        break;
    case TRIGGER_NONE:
    default:
        break;
    }

    return flags;
}

static int set_config_v2(int fd, uint64_t flags)
{
    struct gpio_v2_line_config config;
    memset(&config, 0, sizeof(config));

    config.flags = flags;
    if (ioctl(fd, GPIO_V2_LINE_SET_CONFIG_IOCTL, &config) < 0) {
        return -errno;
    }

    return 0;
}

static int request_line_v2(int fd, unsigned int offset, uint64_t flags, int val)
{
    struct gpio_v2_line_request req;
    memset(&req, 0, sizeof(req));

    req.num_lines = 1;
    req.offsets[0] = offset;
    req.config.flags = flags;
    strcpy(req.consumer, CONSUMER);
    if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
        if (val >= 0) {
            debug("Initializing %d's value to %d on open", offset, val);
            req.config.num_attrs = 1;
            req.config.attrs[0].mask = 1;
            req.config.attrs[0].attr.id = GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES;
            req.config.attrs[0].attr.values = (unsigned int) val;
        } else {
            debug("Not initializing %d's value on open", offset);
        }
    }

    if (ioctl(fd, GPIO_V2_GET_LINE_IOCTL, &req) < 0) {
        return -errno;
    }
    return req.fd;
}

size_t hal_priv_size()
{
    return sizeof(struct hal_cdev_gpio_priv);
}

ERL_NIF_TERM hal_info(ErlNifEnv *env, void *hal_priv, ERL_NIF_TERM info)
{
    enif_make_map_put(env, info, atom_name, enif_make_atom(env, "cdev"), &info);
    (void) hal_priv;
    return info;
}

int hal_load(void *hal_priv)
{
    struct hal_cdev_gpio_priv *priv = hal_priv;
    memset(priv, 0, sizeof(struct hal_cdev_gpio_priv));
    check_bbb_linux_5_15_gpio_change();

    if (pipe(priv->pipe_fds) < 0) {
        error("pipe failed");
        return 1;
    }

    if (enif_thread_create("gpio_poller", &priv->poller_tid, gpio_poller_thread, &priv->pipe_fds[0], NULL) != 0) {
        error("enif_thread_create failed");
        return 1;
    }
    return 0;
}

void hal_unload(void *hal_priv)
{
    debug("hal_unload");
    struct hal_cdev_gpio_priv *priv = hal_priv;

    // Close everything related to the listening thread so that it exits
    close(priv->pipe_fds[0]);
    close(priv->pipe_fds[1]);
    // If the listener thread hasn't exited already, it should do so soon.
    enif_thread_join(priv->poller_tid, NULL);
}

int hal_open_gpio(struct gpio_pin *pin,
                  ErlNifEnv *env)
{
    int gpiochip_fd = open(pin->gpiochip, O_RDWR|O_CLOEXEC);
    if (gpiochip_fd < 0)
        return -errno;

    uint64_t flags = config_to_flags(pin);
    int value = pin->config.is_output ? pin->config.initial_value : -1;

    pin->fd = request_line_v2(gpiochip_fd, pin->offset, flags, value);
    close(gpiochip_fd);
    debug("requesting pin %s:%d -> %d", pin->gpiochip, pin->offset, pin->fd);
    if (pin->fd < 0)
        return pin->fd;

    // Only call hal_apply_interrupts if there's a trigger
    if (pin->config.trigger != TRIGGER_NONE) {
        int rc = hal_apply_interrupts(pin, env);
        if (rc < 0) {
            close(pin->fd);
            return rc;
        }
    }

    return 0;
}

void hal_close_gpio(struct gpio_pin *pin)
{
    debug("hal_close_gpio %s:%d", pin->gpiochip, pin->offset);
    if (pin->fd >= 0) {
        // Turn off interrupts if they're on.
        if (pin->config.trigger != TRIGGER_NONE) {
            pin->config.trigger = TRIGGER_NONE;
            update_polling_thread(pin);
        }
        close(pin->fd);
    }
}

int hal_read_gpio(struct gpio_pin *pin)
{
    debug("hal_read_gpio %s:%d", pin->gpiochip, pin->offset);
    return get_value_v2(pin->fd);
}

int hal_write_gpio(struct gpio_pin *pin, int value, ErlNifEnv *env)
{
    (void) env;
    debug("hal_write_gpio %s:%d -> %d", pin->gpiochip, pin->offset, value);
    return set_value_v2(pin->fd, value);
}

static int refresh_config(const struct gpio_pin *pin)
{
    uint64_t flags = config_to_flags(pin);
    return set_config_v2(pin->fd, flags);
}

int hal_apply_interrupts(struct gpio_pin *pin, ErlNifEnv *env)
{
    (void) env;
    debug("hal_apply_interrupts %s:%d", pin->gpiochip, pin->offset);
    // Update the configuration and start or stop polling
    if (refresh_config(pin) < 0 ||
            update_polling_thread(pin) < 0)
        return -1;

    return 0;
}

int hal_apply_direction(struct gpio_pin *pin)
{
    debug("hal_apply_direction %s:%d", pin->gpiochip, pin->offset);
    return refresh_config(pin);
}

int hal_apply_pull_mode(struct gpio_pin *pin)
{
    debug("hal_apply_pull_mode %s:%d", pin->gpiochip, pin->offset);
    return refresh_config(pin);
}

ERL_NIF_TERM hal_enumerate(ErlNifEnv *env, void *hal_priv)
{
    int i;

    // This code scans GPIOs in reverse order so that the resulting list that
    // is built is in order. Order matters because it looks nice and pin number
    // compatibility with Circuits.GPIO v1 depends on it.
    ERL_NIF_TERM gpio_list = enif_make_list(env, 0);
    for (i = 0; i < 16; i++) {
        char path[32];
        sprintf(path, "/dev/gpiochip%d", gpiochip_order_r[i]);

        int fd = open(path, O_RDONLY|O_CLOEXEC);
        if (fd < 0)
            continue;

        struct gpiochip_info info;
        memset(&info, 0, sizeof(struct gpiochip_info));
        if (ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &info) < 0)
            continue;

        ERL_NIF_TERM chip_label = make_string_binary(env, info.label);
        ERL_NIF_TERM chip_name = make_string_binary(env, info.name);

        int j;
        for (j = info.lines - 1; j >= 0; j--) {
            struct gpio_v2_line_info line;
            memset(&line, 0, sizeof(struct gpio_v2_line_info));
            line.offset = j;
            if (ioctl(fd, GPIO_V2_GET_LINEINFO_IOCTL, &line) >= 0) {
                ERL_NIF_TERM line_map = enif_make_new_map(env);
                ERL_NIF_TERM line_offset = enif_make_int(env, j);
                ERL_NIF_TERM line_label = make_string_binary(env, line.name);

                enif_make_map_put(env, line_map, atom_controller, chip_label, &line_map);
                enif_make_map_put(env, line_map, atom_label, line_label, &line_map);
                enif_make_map_put(env, line_map, atom_location, enif_make_tuple2(env, chip_name, line_offset), &line_map);

                gpio_list = enif_make_list_cell(env, line_map, gpio_list);
            }
        }
        close(fd);
    }
    return gpio_list;
}

int hal_get_status(void *hal_priv, ErlNifEnv *env, const char *gpiochip, int offset, ERL_NIF_TERM *result)
{
    int gpiochip_fd = open(gpiochip, O_RDWR|O_CLOEXEC);
    if (gpiochip_fd < 0)
        return -errno;

    struct gpio_v2_line_info line;
    memset(&line, 0, sizeof(struct gpio_v2_line_info));
    line.offset = offset;
    if (ioctl(gpiochip_fd, GPIO_V2_GET_LINEINFO_IOCTL, &line) < 0) {
        int errno_value = errno;
        close(gpiochip_fd);
        return -errno_value;
    }
    close(gpiochip_fd);

    int is_output = line.flags & GPIO_V2_LINE_FLAG_OUTPUT;
    const char *pull_mode_str;
    if (line.flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP)
        pull_mode_str = "pullup";
    else if (line.flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN)
        pull_mode_str = "pulldown";
    else
        pull_mode_str = "none";

    ERL_NIF_TERM map = enif_make_new_map(env);
    ERL_NIF_TERM consumer = make_string_binary(env, line.consumer);
    enif_make_map_put(env, map, atom_consumer, consumer, &map);
    enif_make_map_put(env, map, enif_make_atom(env, "direction"), enif_make_atom(env, is_output ? "output" : "input"), &map);
    enif_make_map_put(env, map, enif_make_atom(env, "pull_mode"), enif_make_atom(env, pull_mode_str), &map);

    *result = map;
    return 0;
}