Megapixels/libmegapixels/findconfig.c

#include <stdio.h>
#include <unistd.h>

#ifndef SYSCONFDIR
#define SYSCONFDIR "/etc"
#endif
#ifndef DATADIR
#define DATADIR "/usr/share"
#endif

static int
find_device_by_model(char *conffile, char *model)
{
        // Check config/%model.conf in the current working directory
        sprintf(conffile, "config/%s.conf", model);
        if (access(conffile, F_OK) != -1) {
                return 1;
        }

        // Check user overridden /etc/megapixels/config/%model.conf
        sprintf(conffile, "%s/megapixels/config/%s.conf", SYSCONFDIR, model);
        if (access(conffile, F_OK) != -1) {
                return 1;
        }

        // Check packaged /usr/share/megapixels/config/%model.conf
        sprintf(conffile, "%s/megapixels/config/%s.conf", DATADIR, model);
        if (access(conffile, F_OK) != -1) {
                return 1;
        }
        return 0;
}

int
libmegapixels_find_config(char *configfile)
{
        char model[512];
        FILE *fp;

        if (access("/proc/device-tree/compatible", F_OK) == -1) {
                return -1;
        }
        fp = fopen("/proc/device-tree/compatible", "r");
        char *modelptr = model;
        while (1) {
                int c = fgetc(fp);
                if (c == EOF) {
                        *(modelptr) = '\0';
                        return find_device_by_model(configfile, model);
                }
                *(modelptr++) = (char)c;
                if (c == 0) {
                        if (find_device_by_model(configfile, model)) {
                                return 0;
                        }
                        modelptr = model;
                }
        }
        return -1;
}