objects/led_controller.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <dirent.h>
#include <systemd/sd-bus.h>

/*
 * These are control files that are present for each led under
 *'/sys/class/leds/<led_name>/' which are used to trigger action
 * on the respective leds by writing predefined data.
 */
const char *power_ctrl = "brightness";
const char *blink_ctrl = "trigger";
const char *duty_on    = "delay_on";
const char *duty_off   = "delay_off";

/*
 * --------------------------------------------------
 * Given the dbus path, returns the name of the LED
 * --------------------------------------------------
 */
char *get_led_name(const char *dbus_path)
{
    char *led_name = NULL;

    /* Get the led name from /org/openbmc/control/led/<name> */
    led_name = strrchr(dbus_path, '/');
    if(led_name)
    {
        led_name++;
    }

    return led_name;
}

/*
 * -------------------------------------------------------------------------
 * Writes the 'on / off / blink' trigger to leds.
 * -------------------------------------------------------------------------
 */
int write_to_led(const char *name, const char *ctrl_file, const char *value)
{
    /* Generic error reporter. */
    int rc = -1;

    /* To get /sys/class/leds/<name>/<control file> */
    char led_path[128] = {0};

    int len = 0;
    len = snprintf(led_path, sizeof(led_path), 
                   "/sys/class/leds/%s/%s",name, ctrl_file);
    if(len >= sizeof(led_path))
    {
        fprintf(stderr, "Error. LED path is too long. :[%d]\n",len);
        return rc;
    }

    FILE *fp = fopen(led_path,"w");
    if(fp == NULL)
    {
        perror("Error:");
        fprintf(stderr,"Error opening:[%s]\n",led_path);
        return rc;
    }

    rc = fwrite(value, strlen(value), 1, fp);
    if(rc != 1)
    {
        perror("Error:");
        fprintf(stderr, "Error writing to :[%s]\n",led_path);
    }

    fclose(fp);

    /* When we get here, rc would be what it was from writing to the file */
    return (rc == 1) ? 0 : -1;
}

/*
 * ----------------------------------------------------------------
 * Router function for any LED operations that come via dbus
 *----------------------------------------------------------------
 */
static int led_function_router(sd_bus_message *msg, void *user_data,
                               sd_bus_error *ret_error)
{
    /* Generic error reporter. */
    int rc = -1;

    /* Extract the led name from the full dbus path */
    const char *led_path = sd_bus_message_get_path(msg);
    if(led_path == NULL)
    {
        fprintf(stderr, "Error. LED path is empty");
        return sd_bus_reply_method_return(msg, "i", rc);
    }

    char *led_name = get_led_name(led_path);
    if(led_name == NULL)
    {
        fprintf(stderr, "Invalid LED name for path :[%s]\n",led_path);
        return sd_bus_reply_method_return(msg, "i", rc);
    }

    /* Now that we have the LED name, get the Operation. */
    const char *led_function = sd_bus_message_get_member(msg);
    if(led_function == NULL)
    {
        fprintf(stderr, "Null LED function specificed for : [%s]\n",led_name);
        return sd_bus_reply_method_return(msg, "i", rc);
    }

    /* Route the user action to appropriate handlers. */
    if( (strcmp(led_function, "setOn") == 0) ||
        (strcmp(led_function, "setOff") == 0))
    {
        rc = led_stable_state_function(led_name, led_function);
        return sd_bus_reply_method_return(msg, "i", rc);
    }
    else if( (strcmp(led_function, "setBlinkFast") == 0) ||
             (strcmp(led_function, "setBlinkSlow") == 0))
    {
        rc = led_default_blink(led_name, led_function);
        return sd_bus_reply_method_return(msg, "i", rc);
    }
    else if(strcmp(led_function, "GetLedState") == 0)
    {
        char value_str[10] = {0};
        const char *led_state = NULL;

        rc = read_led(led_name, power_ctrl, value_str, sizeof(value_str));
        if(rc >= 0)
        {
            /* LED is active low */
            led_state = strtoul(value_str, NULL, 0) ? "Off" : "On";
        }
        return sd_bus_reply_method_return(msg, "is", rc, led_state);
    }
    else
    {
        fprintf(stderr,"Invalid LED function:[%s]\n",led_function);
    }

    return sd_bus_reply_method_return(msg, "i", rc);
}

/*
 * --------------------------------------------------------------
 * Turn On or Turn Off the LED
 * --------------------------------------------------------------
 */
int led_stable_state_function(char *led_name, char *led_function)
{
    /* Generic error reporter. */
    int rc = -1;

    const char *value = NULL;
    if(strcmp(led_function, "setOn") == 0)
    {
        /* LED active low */
        value = "0";
    }
    else if(strcmp(led_function, "setOff") == 0)
    {
        value  = "255";
    }
    else
    {
        fprintf(stderr,"Invalid LED stable state operation:[%s] \n",led_function);
        return rc;
    }

    /*
     * Before doing anything, need to turn off the blinking
     * if there is one in progress by writing 'none' to trigger
     */
    rc = write_to_led(led_name, blink_ctrl, "none");
    if(rc < 0)
    {
        fprintf(stderr,"Error disabling blink. Function:[%s]\n", led_function);
        return rc;
    }

    /*
     * Open the brightness file and write corresponding values.
     */
    rc = write_to_led(led_name, power_ctrl, value);
    if(rc < 0)
    {
        fprintf(stderr,"Error driving LED. Function:[%s]\n", led_function);
    }

    return rc;
}

//-----------------------------------------------------------------------------------
// Given the on and off duration, applies the action on the specified LED.
//-----------------------------------------------------------------------------------
int blink_led(const char *led_name, const char *on_duration, const char *off_duration)
{
    /* Generic error reporter */
    int rc = -1;

    /* Protocol demands that 'timer' be echoed to 'trigger' */
    rc = write_to_led(led_name, blink_ctrl, "timer");
    if(rc < 0)
    {
        fprintf(stderr,"Error writing timer to Led:[%s]\n", led_name);
        return rc;
    }

    /*
     * After writing 'timer to 'trigger', 2 new files get generated namely
     *'delay_on' and 'delay_off' which are telling the time duration for a
     * particular LED on and off.
     */
    rc = write_to_led(led_name, duty_on, on_duration);
    if(rc < 0)
    {
        fprintf(stderr,"Error writing [%s] to delay_on:[%s]\n",on_duration,led_name);
        return rc;
    }

    rc = write_to_led(led_name, duty_off, off_duration);
    if(rc < 0)
    {
        fprintf(stderr,"Error writing [%s] to delay_off:[%s]\n",off_duration,led_name);
    }

    return rc;
}

/*
 * ----------------------------------------------------
 * Default blink action on the LED.
 * ----------------------------------------------------
 */
int led_default_blink(char *led_name, char *blink_type)
{
    /* Generic error reporter */
    int rc = -1;

    /* How long the LED needs to be in on and off state while blinking */
    const char *on_duration = NULL;
    const char *off_duration = NULL;
    if(strcmp(blink_type, "setBlinkSlow") == 0)
    {
        //*Delay 900 millisec before 'on' and delay 900 millisec before off */
        on_duration = "900";
        off_duration = "900";
    }
    else if(strcmp(blink_type, "setBlinkFast") == 0)
    {
        /* Delay 200 millisec before 'on' and delay 200 millisec before off */
        on_duration = "200";
        off_duration = "200";
    }
    else
    {
        fprintf(stderr,"Invalid blink operation:[%s]\n",blink_type);
        return rc;
    }

    rc = blink_led(led_name, on_duration, off_duration);

    return rc;
}

/*
 * ---------------------------------------------------------------
 * Gets the current value of passed in LED file
 * Mainly used for reading 'brightness'
 * NOTE : It is the responsibility of the caller to allocate
 * sufficient space for buffer. This will read upto user supplied 
 * size -or- entire contents of file whichever is smaller
 * ----------------------------------------------------------------
 */
int read_led(const char *name, const char *ctrl_file, 
             void *value, const size_t len)
{
    /* Generic error reporter. */
    int rc = -1;
    int count = 0;

    if(value == NULL || len <= 0)
    {
        fprintf(stderr, "Invalid buffer passed to LED read\n");
        return rc;
    }

    /* To get /sys/class/leds/<name>/<control file> */
    char led_path[128] = {0};

    int led_len = 0;
    led_len = snprintf(led_path, sizeof(led_path), 
                   "/sys/class/leds/%s/%s",name, ctrl_file);
    if(led_len >= sizeof(led_path))
    {
        fprintf(stderr, "Error. LED path is too long. :[%d]\n",led_len);
        return rc;
    }

    FILE *fp = fopen(led_path,"rb");
    if(fp == NULL)
    {
        perror("Error:");
        fprintf(stderr,"Error opening:[%s]\n",led_path);
        return rc;
    }

    char *sysfs_value = (char *)value;
    while(!feof(fp) && (count < len))
    {
        sysfs_value[count++] = fgetc(fp);
    }
    sysfs_value[count]='\0';

    fclose(fp);
    return 0;
}

/*
 * -----------------------------------------------
 * Dbus Services offered by this LED controller
 * -----------------------------------------------
 */
static const sd_bus_vtable led_control_vtable[] =
{
    SD_BUS_VTABLE_START(0),
    SD_BUS_METHOD("setOn", "", "i", &led_function_router, SD_BUS_VTABLE_UNPRIVILEGED),
    SD_BUS_METHOD("setOff", "", "i", &led_function_router, SD_BUS_VTABLE_UNPRIVILEGED),
    SD_BUS_METHOD("setBlinkFast", "", "i", &led_function_router, SD_BUS_VTABLE_UNPRIVILEGED),
    SD_BUS_METHOD("setBlinkSlow", "", "i", &led_function_router, SD_BUS_VTABLE_UNPRIVILEGED),
    SD_BUS_METHOD("GetLedState", "", "is", &led_function_router, SD_BUS_VTABLE_UNPRIVILEGED),
    SD_BUS_VTABLE_END,
};

/*
 * ---------------------------------------------
 * Interested in all files except standard ones
 * ---------------------------------------------
 */
int led_select(const struct dirent *entry)
{
    if( (strcmp(entry->d_name, ".") == 0) ||
        (strcmp(entry->d_name, "..") == 0))
    {
        return 0;
    }
    return 1;
}

/*
 * ------------------------------------------------
 * Called as part of setting up skeleton services.
 * -----------------------------------------------
 */
int start_led_services()
{
    /* Generic error reporter. */
    int rc = -1;
    int num_leds = 0;
    int count_leds = 0;

    /* Bus and slot where we are offering the LED dbus service. */
    sd_bus *bus_type = NULL;
    sd_bus_slot *led_slot = NULL;

    /* For walking '/sys/class/leds/' looking for names of LED.*/
    struct dirent **led_list;

    /* Get a hook onto system bus. */
    rc = sd_bus_open_system(&bus_type);
    if(rc < 0)
    {
        fprintf(stderr,"Error opening system bus.\n");
        return rc;
    }

    count_leds = num_leds = scandir("/sys/class/leds/", 
                                    &led_list, led_select, alphasort);
    if(num_leds <= 0)
    {
        fprintf(stderr,"No LEDs present in the system\n");

        sd_bus_slot_unref(led_slot);
        sd_bus_unref(bus_type);
        return rc;
    }

    /* Fully qualified Dbus object for a particular LED */
    char led_object[128] = {0};
    int len = 0;

    /* For each led present, announce the service on dbus. */
    while(num_leds--)
    {
        memset(led_object, 0x0, sizeof(led_object));

        len = snprintf(led_object, sizeof(led_object), "%s%s",
                "/org/openbmc/control/led/", led_list[num_leds]->d_name);

        if(len >= sizeof(led_object))
        {
            fprintf(stderr, "Error. LED object is too long:[%d]\n",len);
            rc = -1;
            break;
        }

        /* Install the object */
        rc = sd_bus_add_object_vtable(bus_type,
                                      &led_slot,
                                      led_object,                     /* object path */
                                      "org.openbmc.Led",   /* interface name */
                                      led_control_vtable,
                                      NULL);

        if (rc < 0)
        {
            fprintf(stderr, "Failed to add object to dbus: %s\n", strerror(-rc));
            break;
        }
    }

    /* Done with all registration. */
    while (count_leds > 0)
    {
        free(led_list[--count_leds]);
        if(count_leds == 0)
        {
            free(led_list);
        }
    }

    /* If we had success in adding the providers, request for a bus name. */
    if(rc == 0)
    {
        /* Take one in OpenBmc */
        rc = sd_bus_request_name(bus_type, "org.openbmc.control.led", 0);
        if (rc < 0)
        {
            fprintf(stderr, "Failed to acquire service name: %s\n", strerror(-rc));
        }
        else
        {
            for (;;)
            {
                /* Process requests */
                rc = sd_bus_process(bus_type, NULL);
                if (rc < 0)
                {
                    fprintf(stderr, "Failed to process bus: %s\n", strerror(-rc));
                    break;
                }
                if (rc > 0)
                {
                    continue;
                }

                rc = sd_bus_wait(bus_type, (uint64_t) - 1);
                if (rc < 0)
                {
                    fprintf(stderr, "Failed to wait on bus: %s\n", strerror(-rc));
                    break;
                }
            }
        }
    }
    sd_bus_slot_unref(led_slot);
    sd_bus_unref(bus_type);

    return rc;
}

int main(void)
{
    int rc = 0;

    /* This call is not supposed to return. If it does, then an error */
    rc = start_led_services();
    if(rc < 0)
    {
        fprintf(stderr, "Error starting LED Services. Exiting");
    }

    return rc;
}