rpi-rgb-led-matrix/lib/options-initialize.cc

// -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
// Copyright (C) 2013, 2016 Henner Zeller <h.zeller@acm.org>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation version 2.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://gnu.org/licenses/gpl-2.0.txt>

#include "led-matrix.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <grp.h>
#include <pwd.h>

#include <vector>

namespace rgb_matrix {
RuntimeOptions::RuntimeOptions() :
#ifdef RGB_SLOWDOWN_GPIO
  gpio_slowdown(RGB_SLOWDOWN_GPIO),
#else
  gpio_slowdown(1),
#endif
  daemon(0), drop_privileges(0)
{
  // Nothing to see here.
}

namespace {
typedef char** argv_iterator;

#define OPTION_PREFIX     "--led-"
#define OPTION_PREFIX_LEN strlen(OPTION_PREFIX)

static bool ConsumeBoolFlag(const char *flag_name, const argv_iterator &pos,
                            bool *result_value) {
  const char *option = *pos;
  if (strncmp(option, OPTION_PREFIX, OPTION_PREFIX_LEN) != 0)
    return false;
  option += OPTION_PREFIX_LEN;
  bool value_to_set = true;
  if (strncmp(option, "no-", 3) == 0) {
    value_to_set = false;
    option += 3;
  }
  if (strcmp(option, flag_name) != 0)
    return false;  // not consumed.
  *result_value = value_to_set;
  return true;
}

static bool ConsumeIntFlag(const char *flag_name,
                           argv_iterator &pos, const argv_iterator end,
                           int *result_value, int *error) {
  const char *option = *pos;
  if (strncmp(option, OPTION_PREFIX, OPTION_PREFIX_LEN) != 0)
    return false;
  option += OPTION_PREFIX_LEN;
  const size_t flag_len = strlen(flag_name);
  if (strncmp(option, flag_name, flag_len) != 0)
    return false;  // not consumed.
  const char *value;
  if (option[flag_len] == '=')  // --option=42  # value in same arg
    value = option + flag_len + 1;
  else if (pos + 1 < end) {     // --option 42  # value in next arg
    value = *(++pos);
  } else {
    fprintf(stderr, "Parameter expected after %s%s\n",
            OPTION_PREFIX, flag_name);
    ++*error;
    return true;  // consumed, but error.
  }
  char *end_value = NULL;
  int val = strtol(value, &end_value, 10);
  if (!*value || *end_value) {
    fprintf(stderr, "Couldn't parse parameter %s%s=%s "
            "(Expected decimal number but '%s' looks funny)\n",
            OPTION_PREFIX, flag_name, value, end_value);
    ++*error;
    return true;  // consumed, but error
  }
  *result_value = val;
  return true;  // consumed.
}

static bool FlagInit(int &argc, char **&argv,
                     RGBMatrix::Options *mopts,
                     RuntimeOptions *ropts) {
  argv_iterator it = &argv[0];
  argv_iterator end = it + argc;

  std::vector<char*> unused_options;
  unused_options.push_back(*it++);  // Not interested in program name

  bool bool_scratch;
  int err = 0;
  bool posix_end_option_seen = false;  // end of options '--'
  for (/**/; it < end; ++it) {
    posix_end_option_seen |= (strcmp(*it, "--") == 0);
    if (!posix_end_option_seen) {
      if (ConsumeIntFlag("rows", it, end, &mopts->rows, &err))
        continue;
      if (ConsumeIntFlag("chain", it, end, &mopts->chain_length, &err))
        continue;
      if (ConsumeIntFlag("parallel", it, end, &mopts->parallel, &err))
        continue;
      if (ConsumeIntFlag("brightness", it, end, &mopts->brightness, &err))
        continue;
      if (ConsumeIntFlag("pwm-bits", it, end, &mopts->pwm_bits, &err))
        continue;
      if (ConsumeBoolFlag("show-refresh", it, &mopts->show_refresh_rate))
        continue;
      if (ConsumeBoolFlag("inverse", it, &mopts->inverse_colors))
        continue;
      if (ConsumeBoolFlag("swap-green-blue", it, &mopts->swap_green_blue))
        continue;

      // Runtime options.
      if (ConsumeIntFlag("slowdown-gpio", it, end, &ropts->gpio_slowdown, &err))
        continue;
      if (ropts->daemon >= 0 && ConsumeBoolFlag("daemon", it, &bool_scratch)) {
        ropts->daemon = bool_scratch ? 1 : 0;
        continue;
      }
      if (ropts->drop_privileges >= 0 &&
          ConsumeBoolFlag("drop-privs", it, &bool_scratch)) {
        ropts->drop_privileges = bool_scratch ? 1 : 0;
        continue;
      }
      if (strncmp(*it, OPTION_PREFIX, OPTION_PREFIX_LEN) == 0) {
        fprintf(stderr, "Option %s starts with %s but it is unkown. Typo?\n",
                *it, OPTION_PREFIX);
      }
    }
    unused_options.push_back(*it);
  }

  if (err > 0) {
    return false;
  }

  // Success. Re-arrange flags to only include the ones not consumed.
  argc = (int) unused_options.size();
  for (int i = 0; i < argc; ++i) {
    argv[i] = unused_options[i];
  }
  return true;
}

static bool drop_privs(const char *priv_user, const char *priv_group) {
  uid_t ruid, euid, suid;
  if (getresuid(&ruid, &euid, &suid) >= 0) {
    if (euid != 0)   // not root anyway. No priv dropping.
      return true;
  }

  struct group *g = getgrnam(priv_group);
  if (g == NULL) {
    perror("group lookup.");
    return false;
  }
  if (setresgid(g->gr_gid, g->gr_gid, g->gr_gid) != 0) {
    perror("setresgid()");
    return false;
  }
  struct passwd *p = getpwnam(priv_user);
  if (p == NULL) {
    perror("user lookup.");
    return false;
  }
  if (setresuid(p->pw_uid, p->pw_uid, p->pw_uid) != 0) {
    perror("setresuid()");
    return false;
  }
  return true;
}

}  // namespace

// Public interface.
RGBMatrix *CreateMatrixFromFlags(int *argc, char ***argv,
                                 RGBMatrix::Options *m_opt_in,
                                 RuntimeOptions *rt_opt_in) {
  RGBMatrix::Options scratch_matrix;
  RGBMatrix::Options *mopt = (m_opt_in != NULL) ? m_opt_in : &scratch_matrix;

  RuntimeOptions scratch_rt;
  RuntimeOptions *ropt = (rt_opt_in != NULL) ? rt_opt_in : &scratch_rt;
  if (!FlagInit(*argc, *argv, mopt, ropt)) {
    return NULL;
  }

  std::string error;
  if (!mopt->Validate(&error)) {
    fprintf(stderr, "%s\n", error.c_str());
    return NULL;
  }

  if (getuid() != 0) {
    fprintf(stderr, "Must run as root to be able to access /dev/mem\n"
            "Prepend 'sudo' to the command:\n\tsudo %s ...\n", (*argv)[0]);
    return NULL;
  }

  if (ropt->gpio_slowdown < 0 || ropt->gpio_slowdown > 4) {
    fprintf(stderr, "--led-slowdown-gpio=%d is outside usable range\n",
            ropt->gpio_slowdown);
    return NULL;
  }
  static GPIO io;  // This static var is a little bit icky.
  if (!io.Init(ropt->gpio_slowdown)) {
    return NULL;
  }

  if (ropt->daemon > 0 && daemon(1, 0) != 0) {
    perror("Failed to become daemon");
  }

  RGBMatrix *result = new RGBMatrix(NULL, *mopt);
  // Allowing daemon also means we are allowed to start the thread now.
  const bool allow_daemon = !(ropt->daemon < 0);
  result->SetGPIO(&io, allow_daemon);

  if (ropt->drop_privileges > 0) {
    drop_privs("daemon", "daemon");
  }

  return result;
}

void PrintMatrixFlags(FILE *out, const RGBMatrix::Options &d,
                      const RuntimeOptions &r) {
  fprintf(out,
          "\t--led-rows=<rows>         : Panel rows. 8, 16, 32 or 64. "
          "(Default: %d).\n"
          "\t--led-chain=<chained>     : Number of daisy-chained panels. "
          "(Default: %d).\n"
          "\t--led-parallel=<parallel> : For A/B+ models or RPi2,3b: parallel "
          "chains. range=1..3 (Default: %d).\n"
          "\t--led-pwm-bits=<1..11>    : PWM bits (Default: %d).\n"
          "\t--led-brightness=<percent>: Brightness in percent (Default: %d).\n"
          "\t--led-%sshow-refresh        : %show refresh rate.\n"
          "\t--led-%sinverse             "
          ": Switch if your matrix has inverse colors %s.\n "
          "\t--led-%sswap-green-blue     : Switch if your matrix has green/blue "
          "swapped %s.\n",
          d.rows, d.chain_length, d.parallel,
          d.pwm_bits, d.brightness,
          d.show_refresh_rate ? "no-" : "", d.show_refresh_rate ? "Don't s" : "S",
          d.inverse_colors ? "no-" : "",    d.inverse_colors ? "off" : "on",
          d.swap_green_blue ? "no-" : "",    d.swap_green_blue ? "off" : "on"
          );
  fprintf(out, "\t--led-slowdown-gpio=<0..2>: "
          "Slowdown GPIO. Needed for faster Pis and/or slower panels "
          "(Default: %d).\n", r.gpio_slowdown);
  if (r.daemon >= 0) {
    const bool on = (r.daemon > 0);
    fprintf(out,
            "\t--led-%sdaemon              : "
            "%sake the process run in the background as daemon.\n",
            on ? "no-" : "", on ? "Don't m" : "M");
  }
  if (r.drop_privileges >= 0) {
    const bool on = (r.drop_privileges > 0);
    fprintf(out,
            "\t--led-%sdrop-privs          : %srop privileges from 'root' "
            "after initializing the hardware.\n",
            on ? "no-" : "", on ? "Don't d" : "D");
  }
}

bool RGBMatrix::Options::Validate(std::string *err) {
  bool success = true;
  if (rows != 8 && rows != 16 && rows != 32 && rows != 64) {
    err->append("Invalid number or panel rows. "
                "Should be one of 8, 16, 32 or 64\n");
    success = false;
  }

  if (chain_length < 1) {
    err->append("Chain-length outside usable range\n");
    success = false;
  }

  if (parallel < 1 || parallel > 3) {
    err->append("Parallel outside usable range.\n");
    success = false;
  }

  if (brightness < 1 || brightness > 100) {
    err->append("Brightness is outside usable range.\n");
    success = false;
  }

  if (pwm_bits <= 0 || pwm_bits > 11) {
    err->append("Invalid range of pwm-bits\n");
    success = false;
  }

  return success;
}

}  // namespace rgb_matrix