====== device_getinfo ======

The device_getinfo functions are used by MESS to get additional info about the devices used in a system. They are generally located in the systems/<drivername>.c file.

===== Syntax =====

All data that you want to return must be copied into the info union. A switch is used to selected the info MESS wants. Possible states are:

**DEVINFO_INT_TYPE**

The type of the device. Possible values are:

  * IO_FLOPPY (Floppy drives)
  * IO_PRINTER (Printer)
  * ...

**DEVINFO_INT_READABLE**

Boolean value whether this device can read data. Possible values:

  * 1 - Data can be read from the device (example: floppy drive)
  * 0 - Data cannot be read from the device (example: printer)

**DEVINFO_INT_WRITEABLE**

Boolean value whether this device can write data. Possible values:

  * 1 - Data can be written to the device (example: printer)
  * 0 - Data cannot be written to the device (example: CD-ROM)

**DEVINFO_INT_CREATABLE**

Boolean value whether new files can be created for use with this device or not. Possible values:

  * 1 - A new file can be created for use with this device (example: empty floppy)
  * 0 - New files cannot be created for the device (example: CD-ROM)

**DEVINFO_INT_COUNT**

The number of devices this system can possibly use.

**DEVINFO_INT_MUST_BE_LOADED**

Boolean value whether this system needs a file attached to this device to boot.

  * 1 - Device needs a valid file for this device and won't start without one
  * 0 - System can be started without a valid file attached to this device

**DEVINFO_PTR_LOAD**

This is a pointer to the function which is called when the user mounts a new file for use with this device.

**DEVINFO_STR_FILE_EXTENSIONS**

This is a comma separated list representing the possible file extensions for this device.

===== Example =====

This could be the function for a floppy drive:

<code c>
static void mydriver_floppy_getinfo(const device_class *devclass, UINT32 state, union devinfo *info)
{
	/* floppy */
	switch(state)
	{
		/* --- the following bits of info are returned as 64-bit signed integers --- */
		case DEVINFO_INT_TYPE:            info->i = IO_FLOPPY; break;
		case DEVINFO_INT_READABLE:        info->i = 1; break;
		case DEVINFO_INT_WRITEABLE:       info->i = 1; break;
		case DEVINFO_INT_CREATABLE:       info->i = 1; break;
		case DEVINFO_INT_COUNT:           info->i = 2; break;

		/* --- the following bits of info are returned as pointers to data or functions --- */
		case DEVINFO_PTR_LOAD:            info->load = device_load_mydriver_floppy; break;

		/* --- the following bits of info are returned as NULL-terminated strings --- */
		case DEVINFO_STR_FILE_EXTENSIONS: strcpy(info->s = device_temp_str(), "dsk"); break;
	}
}
</code>

In this example, we create a device of type IO_FLOPPY, that is readable, writable and creatable. The system supports two floppy drives. The function device_load_mydriver_floppy is called when the user mounts a new file (we don't actually write this function as is, we use the macro [[device_load|DEVICE_LOAD]]). The file extension is just ''dsk''.

===== See also =====

{{topic>reference +devices&list&nodate&nouser&notags}}

{{tag>reference mess devices}}