/*
 * Copyright © 2007, 2011, 2013, 2014, 2015 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Eric Anholt <eric@anholt.net>
 *    Daniel Vetter <daniel.vetter@ffwll.ch>
 *
 */

#ifndef ANDROID
#define _GNU_SOURCE
#else
#include <libgen.h>
#endif
#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <string.h>
#include <sys/mman.h>
#include <signal.h>
#include <pciaccess.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/syscall.h>
#include <sys/utsname.h>
#include <termios.h>
#include <assert.h>

#include "drmtest.h"
#include "i915_drm.h"
#include "intel_chipset.h"
#include "igt_aux.h"
#include "igt_debugfs.h"
#include "igt_gt.h"
#include "config.h"
#include "intel_reg.h"
#include "ioctl_wrappers.h"
#include "igt_kms.h"
#include "igt_pm.h"

/**
 * SECTION:igt_aux
 * @short_description: Auxiliary libraries and support functions
 * @title: aux
 * @include: igt.h
 *
 * This library provides various auxiliary helper functions that don't really
 * fit into any other topic.
 */


/* signal interrupt helpers */
static struct igt_helper_process signal_helper;
long long int sig_stat;
static void __attribute__((noreturn)) signal_helper_process(pid_t pid)
{
	/* Interrupt the parent process at 500Hz, just to be annoying */
	while (1) {
		usleep(1000 * 1000 / 500);
		if (kill(pid, SIGCONT)) /* Parent has died, so must we. */
			exit(0);
	}
}

static void sig_handler(int i)
{
	sig_stat++;
}

/**
 * igt_fork_signal_helper:
 *
 * Fork a child process using #igt_fork_helper to interrupt the parent process
 * with a SIGCONT signal at regular quick intervals. The corresponding dummy
 * signal handler is installed in the parent process.
 *
 * This is useful to exercise ioctl error paths, at least where those can be
 * exercises by interrupting blocking waits, like stalling for the gpu. This
 * helper can also be used from children spawned with #igt_fork.
 *
 * In tests with subtests this function can be called outside of failure
 * catching code blocks like #igt_fixture or #igt_subtest.
 */
void igt_fork_signal_helper(void)
{
	if (igt_only_list_subtests())
		return;

	/* We pick SIGCONT as it is a "safe" signal - if we send SIGCONT to
	 * an unexpecting process it spuriously wakes up and does nothing.
	 * Most other signals (e.g. SIGUSR1) cause the process to die if they
	 * are not handled. This is an issue in case the sighandler is not
	 * inherited correctly (or if there is a race in the inheritance
	 * and we send the signal at exactly the wrong time).
	 */
	signal(SIGCONT, sig_handler);
	setpgrp(); /* define a new process group for the tests */

	igt_fork_helper(&signal_helper) {
		setpgrp(); /* Escape from the test process group */

		/* Pass along the test process group identifier,
		 * negative pid => send signal to everyone in the group.
		 */
		signal_helper_process(-getppid());
	}
}

/**
 * igt_stop_signal_helper:
 *
 * Stops the child process spawned with igt_fork_signal_helper() again.
 *
 * In tests with subtests this function can be called outside of failure
 * catching code blocks like #igt_fixture or #igt_subtest.
 */
void igt_stop_signal_helper(void)
{
	if (igt_only_list_subtests())
		return;

	igt_stop_helper(&signal_helper);

	sig_stat = 0;
}

/**
 * igt_check_boolean_env_var:
 * @env_var: environment variable name
 * @default_value: default value for the environment variable
 *
 * This function should be used to parse boolean environment variable options.
 *
 * Returns:
 * The boolean value of the environment variable @env_var as decoded by atoi()
 * if it is set and @default_value if the variable is not set.
 */
bool igt_check_boolean_env_var(const char *env_var, bool default_value)
{
	char *val;

	val = getenv(env_var);
	if (!val)
		return default_value;

	return atoi(val) != 0;
}

/**
 * igt_aub_dump_enabled:
 *
 * Returns:
 * True if AUB dumping is enabled with IGT_DUMP_AUB=1 in the environment, false
 * otherwise.
 */
bool igt_aub_dump_enabled(void)
{
	static int dump_aub = -1;

	if (dump_aub == -1)
		dump_aub = igt_check_boolean_env_var("IGT_DUMP_AUB", false);

	return dump_aub;
}

/* other helpers */
/**
 * igt_exchange_int:
 * @array: pointer to the array of integers
 * @i: first position
 * @j: second position
 *
 * Exchanges the two values at array indices @i and @j. Useful as an exchange
 * function for igt_permute_array().
 */
void igt_exchange_int(void *array, unsigned i, unsigned j)
{
	int *int_arr, tmp;
	int_arr = array;

	tmp = int_arr[i];
	int_arr[i] = int_arr[j];
	int_arr[j] = tmp;
}

static uint32_t
hars_petruska_f54_1_random_unsafe(void)
{
	static uint32_t state = 0x12345678;
#define rol(x,k) ((x << k) | (x >> (32-k)))
	return state = (state ^ rol (state, 5) ^ rol (state, 24)) + 0x37798849;
#undef rol
}

/**
 * igt_permute_array:
 * @array: pointer to array
 * @size: size of the array
 * @exchange_func: function to exchange array elements
 *
 * This function randomly permutes the array using random() as the PRNG source.
 * The @exchange_func function is called to exchange two elements in the array
 * when needed.
 */
void igt_permute_array(void *array, unsigned size,
                       void (*exchange_func)(void *array,
                                             unsigned i,
                                             unsigned j))
{
	int i;

	for (i = size - 1; i > 1; i--) {
		/* yes, not perfectly uniform, who cares */
		long l = hars_petruska_f54_1_random_unsafe() % (i +1);
		if (i != l)
			exchange_func(array, i, l);
	}
}

__attribute__((format(printf, 1, 2)))
static void igt_interactive_info(const char *format, ...)
{
	va_list args;

	if (!isatty(STDERR_FILENO) || __igt_plain_output)
		return;

	if (igt_log_level > IGT_LOG_INFO)
		return;

	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
}


/**
 * igt_progress:
 * @header: header string to prepend to the progress indicator
 * @i: work processed thus far
 * @total: total amount of work
 *
 * This function draws a progress indicator, which is useful for running
 * long-winded tests manually on the console. To avoid spamming log files in
 * automated runs the progress indicator is suppressed when not running on a
 * terminal.
 */
void igt_progress(const char *header, uint64_t i, uint64_t total)
{
	int divider = 200;

	if (i+1 >= total) {
		igt_interactive_info("\r%s100%%\n", header);
		return;
	}

	if (total / 200 == 0)
		divider = 1;

	/* only bother updating about every 0.5% */
	if (i % (total / divider) == 0)
		igt_interactive_info("\r%s%3llu%%", header,
				     (long long unsigned)i * 100 / total);
}

/**
 * igt_print_activity:
 *
 * Print a '.' to indicate activity. This is printed without a newline and
 * only if output is to a terminal.
 */
void igt_print_activity(void)
{
	igt_interactive_info(".");
}

/* mappable aperture trasher helper */
drm_intel_bo **trash_bos;
int num_trash_bos;

/**
 * igt_init_aperture_trashers:
 * @bufmgr: libdrm buffer manager
 *
 * Initialize the aperture trasher using @bufmgr, which can then be run with
 * igt_trash_aperture().
 */
void igt_init_aperture_trashers(drm_intel_bufmgr *bufmgr)
{
	int i;

	num_trash_bos = gem_mappable_aperture_size() / (1024*1024);

	trash_bos = malloc(num_trash_bos * sizeof(drm_intel_bo *));
	igt_assert(trash_bos);

	for (i = 0; i < num_trash_bos; i++)
		trash_bos[i] = drm_intel_bo_alloc(bufmgr, "trash bo", 1024*1024, 4096);
}

/**
 * igt_trash_aperture:
 *
 * Trash the aperture by walking a set of GTT memory mapped objects.
 */
void igt_trash_aperture(void)
{
	int i;
	uint8_t *gtt_ptr;

	for (i = 0; i < num_trash_bos; i++) {
		drm_intel_gem_bo_map_gtt(trash_bos[i]);
		gtt_ptr = trash_bos[i]->virtual;
		*gtt_ptr = 0;
		drm_intel_gem_bo_unmap_gtt(trash_bos[i]);
	}
}

/**
 * igt_cleanup_aperture_trashers:
 *
 * Clean up all aperture trasher state set up with igt_init_aperture_trashers().
 */
void igt_cleanup_aperture_trashers(void)
{
	int i;

	for (i = 0; i < num_trash_bos; i++)
		drm_intel_bo_unreference(trash_bos[i]);

	free(trash_bos);
}

/**
 * igt_system_suspend_autoresume:
 *
 * Execute a system suspend-to-mem cycle and automatically wake up again using
 * the firmware's resume timer.
 *
 * This is very handy for implementing any kind of suspend/resume test.
 */
void igt_system_suspend_autoresume(void)
{
	int ret;

	/* FIXME: Simulation doesn't like suspend/resume, and not even a lighter
	 * approach using /sys/power/pm_test to just test our driver's callbacks
	 * seems to fare better. We need to investigate what's going on. */
	igt_skip_on_simulation();

	/* skip if system doesn't support suspend-to-mem */
	igt_skip_on(system("rtcwake -n -s 30 -m mem") != 0);

	ret = system("rtcwake -s 30 -m mem");
	igt_assert_f(ret == 0,
		     "This failure means that something is wrong with the "
		     "rtcwake tool or how your distro is set up. This is not "
		     "a i915.ko or i-g-t bug.\n");
}

/**
 * igt_system_hibernate_autoresume:
 *
 * Execute a system suspend-to-disk cycle and automatically wake up again using
 * the firmware's resume timer.
 *
 * This is very handy for implementing any kind of hibernate/resume test.
 */
void igt_system_hibernate_autoresume(void)
{
	int ret;

	/* FIXME: I'm guessing simulation behaves the same way as with
	 * suspend/resume, but it might be prudent to make sure
	 */
	/* FIXME: Simulation doesn't like suspend/resume, and not even a lighter
	 * approach using /sys/power/pm_test to just test our driver's callbacks
	 * seems to fare better. We need to investigate what's going on. */
	igt_skip_on_simulation();

	/* skip if system doesn't support suspend-to-disk */
	igt_skip_on(system("rtcwake -n -s 90 -m disk") != 0);

	/* The timeout might need to be adjusted if hibernation takes too long
	 * or if we have to wait excessively long before resume
	 */
	ret = system("rtcwake -s 90 -m disk");
	igt_assert_f(ret == 0,
		     "This failure means that something is wrong with the "
		     "rtcwake tool or how your distro is set up. This is not "
		     "a i915.ko or i-g-t bug.\n");
}

/**
 * igt_drop_root:
 *
 * Drop root privileges and make sure it actually worked. Useful for tests
 * which need to check security constraints. Note that this should only be
 * called from manually forked processes, since the lack of root privileges
 * will wreak havoc with the automatic cleanup handlers.
 */
void igt_drop_root(void)
{
	igt_assert(getuid() == 0);

	igt_assert(setgid(2) == 0);
	igt_assert(setuid(2) == 0);

	igt_assert(getgid() == 2);
	igt_assert(getuid() == 2);
}

/**
 * igt_debug_wait_for_keypress:
 * @var: var lookup to to enable this wait
 *
 * Waits for a key press when run interactively and when the corresponding debug
 * var is set in the --interactive-debug=<var> variable. Multiple keys
 * can be specified as a comma-separated list or alternatively "all" if a wait
 * should happen for all cases.
 *
 * When not connected to a terminal interactive_debug is ignored
 * and execution immediately continues.
 *
 * This is useful for display tests where under certain situation manual
 * inspection of the display is useful. Or when running a testcase in the
 * background.
 */
void igt_debug_wait_for_keypress(const char *var)
{
	struct termios oldt, newt;

	if (!isatty(STDIN_FILENO))
		return;

	if (!igt_interactive_debug)
		return;

	if (!strstr(igt_interactive_debug, var) &&
	    !strstr(igt_interactive_debug, "all"))
		return;

	igt_info("Press any key to continue ...\n");

	tcgetattr ( STDIN_FILENO, &oldt );
	newt = oldt;
	newt.c_lflag &= ~( ICANON | ECHO );
	tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
	getchar();
	tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );
}

/**
 * igt_debug_manual_check:
 * @var: var lookup to to enable this wait
 * @expected: message to be printed as expected behaviour before wait for keys Y/n
 *
 * Waits for a key press when run interactively and when the corresponding debug
 * var is set in the --interactive-debug=<var> variable. Multiple vars
 * can be specified as a comma-separated list or alternatively "all" if a wait
 * should happen for all cases.
 *
 * This is useful for display tests where under certain situation manual
 * inspection of the display is useful. Or when running a testcase in the
 * background.
 *
 * When not connected to a terminal interactive_debug is ignored
 * and execution immediately continues. For this reason by default this function
 * returns true. It returns false only when N/n is pressed indicating the
 * user isn't seeing what was expected.
 *
 * Force test fail when N/n is pressed.
 */
void igt_debug_manual_check(const char *var, const char *expected)
{
	struct termios oldt, newt;
	char key;

	if (!isatty(STDIN_FILENO))
		return;

	if (!igt_interactive_debug)
		return;

	if (!strstr(igt_interactive_debug, var) &&
	    !strstr(igt_interactive_debug, "all"))
		return;

	igt_info("Is %s [Y/n]", expected);

	tcgetattr ( STDIN_FILENO, &oldt );
	newt = oldt;
	newt.c_lflag &= ~ICANON;
	tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
	key = getchar();
	tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );

	igt_info("\n");

	igt_assert(key != 'n' && key != 'N');
}

#define POWER_DIR "/sys/devices/pci0000:00/0000:00:02.0/power"
/* We just leak this on exit ... */
int pm_status_fd = -1;

/**
 * igt_setup_runtime_pm:
 *
 * Sets up the runtime PM helper functions and enables runtime PM. To speed up
 * tests the autosuspend delay is set to 0.
 *
 * Returns:
 * True if runtime pm is available, false otherwise.
 */
bool igt_setup_runtime_pm(void)
{
	int fd;
	ssize_t size;
	char buf[6];

	if (pm_status_fd >= 0)
		return true;

	igt_pm_enable_audio_runtime_pm();

	/* Our implementation uses autosuspend. Try to set it to 0ms so the test
	 * suite goes faster and we have a higher probability of triggering race
	 * conditions. */
	fd = open(POWER_DIR "/autosuspend_delay_ms", O_WRONLY);
	igt_assert_f(fd >= 0,
		     "Can't open " POWER_DIR "/autosuspend_delay_ms\n");

	/* If we fail to write to the file, it means this system doesn't support
	 * runtime PM. */
	size = write(fd, "0\n", 2);

	close(fd);

	if (size != 2)
		return false;

	/* We know we support runtime PM, let's try to enable it now. */
	fd = open(POWER_DIR "/control", O_RDWR);
	igt_assert_f(fd >= 0, "Can't open " POWER_DIR "/control\n");

	size = write(fd, "auto\n", 5);
	igt_assert(size == 5);

	lseek(fd, 0, SEEK_SET);
	size = read(fd, buf, ARRAY_SIZE(buf));
	igt_assert(size == 5);
	igt_assert(strncmp(buf, "auto\n", 5) == 0);

	close(fd);

	pm_status_fd = open(POWER_DIR "/runtime_status", O_RDONLY);
	igt_assert_f(pm_status_fd >= 0,
		     "Can't open " POWER_DIR "/runtime_status\n");

	return true;
}

/**
 * igt_get_runtime_pm_status:
 *
 * Returns: The current runtime PM status.
 */
enum igt_runtime_pm_status igt_get_runtime_pm_status(void)
{
	ssize_t n_read;
	char buf[32];

	lseek(pm_status_fd, 0, SEEK_SET);
	n_read = read(pm_status_fd, buf, ARRAY_SIZE(buf));
	igt_assert(n_read >= 0);
	buf[n_read] = '\0';

	if (strncmp(buf, "suspended\n", n_read) == 0)
		return IGT_RUNTIME_PM_STATUS_SUSPENDED;
	else if (strncmp(buf, "active\n", n_read) == 0)
		return IGT_RUNTIME_PM_STATUS_ACTIVE;
	else if (strncmp(buf, "suspending\n", n_read) == 0)
		return IGT_RUNTIME_PM_STATUS_SUSPENDING;
	else if (strncmp(buf, "resuming\n", n_read) == 0)
		return IGT_RUNTIME_PM_STATUS_RESUMING;

	igt_assert_f(false, "Unknown status %s\n", buf);
	return IGT_RUNTIME_PM_STATUS_UNKNOWN;
}

/**
 * igt_wait_for_pm_status:
 * @status: desired runtime PM status
 *
 * Waits until for the driver to switch to into the desired runtime PM status,
 * with a 10 second timeout.
 *
 * Returns:
 * True if the desired runtime PM status was attained, false if the operation
 * timed out.
 */
bool igt_wait_for_pm_status(enum igt_runtime_pm_status status)
{
	return igt_wait(igt_get_runtime_pm_status() == status, 10000, 100);
}

/* Functions with prefix kmstest_ independent of cairo library are pulled out
 * from file igt_kms.c since this file is skipped in lib/Android.mk when flag
 * ANDROID_HAS_CAIRO is 0. This ensures the usability of these functions even
 * when cairo library is not present on Android.
 */

struct type_name {
	int type;
	const char *name;
};

#define type_name_fn(res) \
const char * kmstest_##res##_str(int type) {		\
	unsigned int i;					\
	for (i = 0; i < ARRAY_SIZE(res##_names); i++) { \
		if (res##_names[i].type == type)	\
			return res##_names[i].name;	\
	}						\
	return "(invalid)";				\
}

struct type_name encoder_type_names[] = {
	{ DRM_MODE_ENCODER_NONE, "none" },
	{ DRM_MODE_ENCODER_DAC, "DAC" },
	{ DRM_MODE_ENCODER_TMDS, "TMDS" },
	{ DRM_MODE_ENCODER_LVDS, "LVDS" },
	{ DRM_MODE_ENCODER_TVDAC, "TVDAC" },
};

type_name_fn(encoder_type)

struct type_name connector_status_names[] = {
	{ DRM_MODE_CONNECTED, "connected" },
	{ DRM_MODE_DISCONNECTED, "disconnected" },
	{ DRM_MODE_UNKNOWNCONNECTION, "unknown" },
};

type_name_fn(connector_status)

struct type_name connector_type_names[] = {
	{ DRM_MODE_CONNECTOR_Unknown, "unknown" },
	{ DRM_MODE_CONNECTOR_VGA, "VGA" },
	{ DRM_MODE_CONNECTOR_DVII, "DVI-I" },
	{ DRM_MODE_CONNECTOR_DVID, "DVI-D" },
	{ DRM_MODE_CONNECTOR_DVIA, "DVI-A" },
	{ DRM_MODE_CONNECTOR_Composite, "composite" },
	{ DRM_MODE_CONNECTOR_SVIDEO, "s-video" },
	{ DRM_MODE_CONNECTOR_LVDS, "LVDS" },
	{ DRM_MODE_CONNECTOR_Component, "component" },
	{ DRM_MODE_CONNECTOR_9PinDIN, "9-pin DIN" },
	{ DRM_MODE_CONNECTOR_DisplayPort, "DP" },
	{ DRM_MODE_CONNECTOR_HDMIA, "HDMI-A" },
	{ DRM_MODE_CONNECTOR_HDMIB, "HDMI-B" },
	{ DRM_MODE_CONNECTOR_TV, "TV" },
	{ DRM_MODE_CONNECTOR_eDP, "eDP" },
};

type_name_fn(connector_type)


/**
 * igt_lock_mem:
 * @size: the amount of memory to lock into RAM, in MB
 *
 * Allocate @size MB of memory and lock it into RAM. This releases any
 * previously locked memory.
 *
 * Use #igt_unlock_mem to release the currently locked memory.
 */
static char *locked_mem;
static size_t locked_size;

void igt_lock_mem(size_t size)
{
	long pagesize = sysconf(_SC_PAGESIZE);
	size_t i;
	int ret;

	if (size == 0) {
		return;
	}

	if (locked_mem) {
		igt_unlock_mem();
		igt_warn("Unlocking previously locked memory.\n");
	}

	locked_size = size * 1024 * 1024;

	locked_mem = malloc(locked_size);
	igt_require_f(locked_mem,
		      "Could not allocate enough memory to lock.\n");

	/* write into each page to ensure it is allocated */
	for (i = 0; i < locked_size; i += pagesize)
		locked_mem[i] = i;

	ret = mlock(locked_mem, locked_size);
	igt_assert_f(ret == 0, "Could not lock memory into RAM.\n");
}

/**
 * igt_unlock_mem:
 *
 * Release and free the RAM used by #igt_lock_mem.
 */
void igt_unlock_mem(void)
{
	if (!locked_mem)
		return;

	munlock(locked_mem, locked_size);

	free(locked_mem);
	locked_mem = NULL;
}


#define MODULE_PARAM_DIR "/sys/module/i915/parameters/"
#define PARAM_NAME_MAX_SZ 32
#define PARAM_VALUE_MAX_SZ 16
#define PARAM_FILE_PATH_MAX_SZ (strlen(MODULE_PARAM_DIR) + PARAM_NAME_MAX_SZ)

struct module_param_data {
	char name[PARAM_NAME_MAX_SZ];
	char original_value[PARAM_VALUE_MAX_SZ];

	struct module_param_data *next;
};
struct module_param_data *module_params = NULL;

static void igt_module_param_exit_handler(int sig)
{
	const size_t dir_len = strlen(MODULE_PARAM_DIR);
	char file_path[PARAM_FILE_PATH_MAX_SZ];
	struct module_param_data *data;
	int fd;

	/* We don't need to assert string sizes on this function since they were
	 * already checked before being stored on the lists. Besides,
	 * igt_assert() is not AS-Safe. */
	strcpy(file_path, MODULE_PARAM_DIR);

	for (data = module_params; data != NULL; data = data->next) {
		strcpy(file_path + dir_len, data->name);

		fd = open(file_path, O_RDWR);
		if (fd >= 0) {
			int size = strlen (data->original_value);

			if (size != write(fd, data->original_value, size)) {
				const char msg[] = "WARNING: Module parameters "
					"may not have been reset to their "
					"original values\n";
				assert(write(STDERR_FILENO, msg, sizeof(msg))
				       == sizeof(msg));
			}

			close(fd);
		}
	}
	/* free() is not AS-Safe, so we can't call it here. */
}

/**
 * igt_save_module_param:
 * @name: name of the i915.ko module parameter
 * @file_path: full sysfs file path for the parameter
 *
 * Reads the current value of an i915.ko module parameter, saves it on an array,
 * then installs an exit handler to restore it when the program exits.
 *
 * It is safe to call this function multiple times for the same parameter.
 *
 * Notice that this function is called by igt_set_module_param(), so that one -
 * or one of its wrappers - is the only function the test programs need to call.
 */
static void igt_save_module_param(const char *name, const char *file_path)
{
	struct module_param_data *data;
	size_t n;
	int fd;

	/* Check if this parameter is already saved. */
	for (data = module_params; data != NULL; data = data->next)
		if (strncmp(data->name, name, PARAM_NAME_MAX_SZ) == 0)
			return;

	if (!module_params)
		igt_install_exit_handler(igt_module_param_exit_handler);

	data = calloc(1, sizeof (*data));
	igt_assert(data);

	strncpy(data->name, name, PARAM_NAME_MAX_SZ);

	fd = open(file_path, O_RDONLY);
	igt_assert(fd >= 0);

	n = read(fd, data->original_value, PARAM_VALUE_MAX_SZ);
	igt_assert_f(n > 0 && n < PARAM_VALUE_MAX_SZ,
		     "Need to increase PARAM_VALUE_MAX_SZ\n");

	igt_assert(close(fd) == 0);

	data->next = module_params;
	module_params = data;
}

/**
 * igt_set_module_param:
 * @name: i915.ko parameter name
 * @val: i915.ko parameter value
 *
 * This function sets the desired value for the given i915.ko parameter. It also
 * takes care of saving and restoring the values that were already set before
 * the test was run.
 *
 * Please consider using igt_set_module_param_int() for the integer and bool
 * parameters.
 */
void igt_set_module_param(const char *name, const char *val)
{
	char file_path[PARAM_FILE_PATH_MAX_SZ];
	size_t len = strlen(val);
	int fd;

	igt_assert_f(strlen(name) < PARAM_NAME_MAX_SZ,
		     "Need to increase PARAM_NAME_MAX_SZ\n");
	strcpy(file_path, MODULE_PARAM_DIR);
	strcpy(file_path + strlen(MODULE_PARAM_DIR), name);

	igt_save_module_param(name, file_path);

	fd = open(file_path, O_RDWR);
	igt_assert(write(fd, val, len) == len);
	igt_assert(close(fd) == 0);
}

/**
 * igt_set_module_param_int:
 * @name: i915.ko parameter name
 * @val: i915.ko parameter value
 *
 * This is a wrapper for igt_set_module_param() that takes an integer instead of
 * a string. Please see igt_set_module_param().
 */
void igt_set_module_param_int(const char *name, int val)
{
	char str[PARAM_VALUE_MAX_SZ];
	int n;

	n = snprintf(str, PARAM_VALUE_MAX_SZ, "%d\n", val);
	igt_assert_f(n < PARAM_VALUE_MAX_SZ,
		     "Need to increase PARAM_VALUE_MAX_SZ\n");

	igt_set_module_param(name, str);
}