acdcontrol.py

#! /usr/bin/env python3
"""This program allows changing brightness on some Apple displays.
"""
__author__ = 'Victor Varvariuc <victor.varvariuc@gmail.com>'

import argparse
import struct
import ctypes
import fcntl
import os
import sys
from collections import OrderedDict

import ioctl


SUPPORTED_DEVICES = {
    (0x05ac, 'Apple'): (
        # prod id, name, (min brightness, max brightness) or None if unknown
        (0x9215, 'Apple Studio Display 15"', None),
        (0x9217, 'Apple Studio Display 17"', None),
        (0x9218, 'Apple Cinema Display 23"', None),
        (0x9219, 'Apple Cinema Display 20"', None),
        (0x921e, 'Apple Cinema Display 24"', None),
        (0x9226, 'Apple Cinema HD Display 27"', None),
        (0x9227, 'Apple Cinema HD Display 27" 2013', None),
        (0x9232, 'Apple Cinema HD Display 30"', None),
        (0x9236, 'Apple LED Cinema Display 24"', (0, 255)),
    ),
    (0x0419, 'Samsung Electronics'): (
        (0x8002, 'Samsung SyncMaster 757NF'),
    ),
}

# -------------------------------------------------------------------------------------------------
class StructMeta(type(ctypes.Structure)):
    @classmethod
    def __prepare__(metacls, cls_name, cls_bases):
        """Use this ordered dict as class dictionary during class definition.
        """
        return OrderedDict()

    def __new__(metacls, cls_name, cls_bases, cls_dict):
        fields = []
        for field_name, field in list(cls_dict.items()):
            if isinstance(field, type) and issubclass(field, ctypes._SimpleCData):
                fields.append((field_name, field))
                del cls_dict[field_name]
        cls_dict['_fields_'] = fields
        result = super(StructMeta, metacls).__new__(
            metacls, cls_name, cls_bases, dict(cls_dict))
        return result

    def __len__(self):
        """Byte length."""
        _format = ''.join(field[1]._type_ for field in self._fields_)
        return struct.calcsize(_format)


class Struct(ctypes.Structure, metaclass=StructMeta):
    def __repr__(self):
        values = []
        for field_name, _ in self._fields_:
            value = getattr(self, field_name)
            value = hex(value) if isinstance(value, int) else repr(value)
            values.append('%s=%s' % (field_name, value))
        return '%s(%s)' % (self.__class__.__name__, ', '.join(values))


# /usr/src/linux-headers-3.11.0-14/include/uapi/linux/hiddev.h
# -------------------------------------------------------------------------------------------------
# Structures

class hid_version(Struct):
    v3 = ctypes.c_ubyte
    v2 = ctypes.c_ubyte
    v1 = ctypes.c_ushort


class hiddev_devinfo(Struct):
    bustype = ctypes.c_uint
    busnum = ctypes.c_uint
    devnum = ctypes.c_uint
    ifnum = ctypes.c_uint
    vendor = ctypes.c_ushort
    product = ctypes.c_ushort
    version = ctypes.c_ushort
    num_applications = ctypes.c_uint


class hiddev_usage_ref(Struct):
    report_type = ctypes.c_uint
    report_id = ctypes.c_uint
    field_index = ctypes.c_uint
    usage_index = ctypes.c_uint
    usage_code = ctypes.c_uint
    value = ctypes.c_int


class hiddev_report_info(Struct):
    report_type = ctypes.c_uint
    report_id = ctypes.c_uint
    num_fields = ctypes.c_uint


HID_REPORT_ID_UNKNOWN = 0xffffffff
HID_REPORT_ID_FIRST = 0x00000100
HID_REPORT_ID_NEXT = 0x00000200
HID_REPORT_ID_MASK = 0x000000ff
HID_REPORT_ID_MAX = 0x000000ff

HID_REPORT_TYPE_INPUT = 1
HID_REPORT_TYPE_OUTPUT = 2
HID_REPORT_TYPE_FEATURE = 3
HID_REPORT_TYPE_MIN = 1
HID_REPORT_TYPE_MAX = 3

# -------------------------------------------------------------------------------------------------
# IOCTLs (0x00 - 0x7f)

HIDIOCGVERSION = ioctl.IOR(ord('H'), 0x01, len(hid_version))
HIDIOCAPPLICATION = ioctl.IO(ord('H'), 0x02)
HIDIOCGDEVINFO = ioctl.IOR(ord('H'), 0x03, len(hiddev_devinfo))
# HIDIOCGSTRING = ioctl.IOR(ord('H'), 0x04, len(hiddev_string_descriptor))
HIDIOCINITREPORT = ioctl.IO(ord('H'), 0x05)
# HIDIOCGNAME(len)	_IOC(_IOC_READ, 'H', 0x06, len)
HIDIOCGREPORT = ioctl.IOW(ord('H'), 0x07, len(hiddev_report_info))
HIDIOCSREPORT = ioctl.IOW(ord('H'), 0x08, len(hiddev_report_info))
HIDIOCGREPORTINFO = ioctl.IOWR(ord('H'), 0x09, len(hiddev_report_info))
# HIDIOCGFIELDINFO	_IOWR('H', 0x0A, struct hiddev_field_info)
HIDIOCGUSAGE = ioctl.IOWR(ord('H'), 0x0B, len(hiddev_usage_ref))  # get
HIDIOCSUSAGE = ioctl.IOW(ord('H'), 0x0C, len(hiddev_usage_ref))  # set
HIDIOCGUCODE = ioctl.IOWR(ord('H'), 0x0D, len(hiddev_usage_ref))
HIDIOCGFLAG = ioctl.IOR(ord('H'), 0x0E, struct.calcsize(ctypes.c_ushort._type_))
# HIDIOCSFLAG		_IOW('H', 0x0F, int)
HIDIOCGCOLLECTIONINDEX = ioctl.IOW(ord('H'), 0x10, len(hiddev_usage_ref))
# HIDIOCGCOLLECTIONINFO	_IOWR('H', 0x11, struct hiddev_collection_info)
# HIDIOCGPHYS(len)	_IOC(_IOC_READ, 'H', 0x12, len)

# -------------------------------------------------------------------------------------------------
BRIGHTNESS_CONTROL = 16
USAGE_CODE = 0x820010
# -------------------------------------------------------------------------------------------------

class DeviceNotSupported(Exception):
    pass

class AppleCinemaDisplay:
    def __init__(self, device):
        self.device_handle = os.open(device, os.O_RDWR)

        self.device_info = hiddev_devinfo()
        fcntl.ioctl(self.device_handle, HIDIOCGDEVINFO, self.device_info)

        for (vendor_id, vendor_name), products in SUPPORTED_DEVICES.items():
            if self.device_info.vendor == vendor_id:
                break
        else:
            raise DeviceNotSupported('Vendor %04x is not '
                                     'supported.' % self.device_info.vendor)

        self.vendor_name = vendor_name
        self.vendor_id = vendor_id

        for product_id, product_name, clamp in products:
            if self.device_info.product == product_id:
                break
        else:
            raise DeviceNotSupported('Product %04x is not '
                                     'supported.' % self.device_info.product)

        self.product_name = product_name
        self.product_id = product_id
        self.clamp = clamp or (-sys.maxsize, sys.maxsize)


        # Now that we have the number of applications, we can retrieve them
        # using the HIDIOCAPPLICATION ioctl() call
        # applications are indexed from 0..{num_applications-1}
        for app_num in range(self.device_info.num_applications):
            application = fcntl.ioctl(self.device_handle, HIDIOCAPPLICATION,
                                      app_num)
            # The magic values come from various usage table specs
            if (application >> 16) & 0xFF == 0x80:
                break
        else:
            raise DeviceNotSupported('The device is not a USB monitor.')

        # Initialise the internal report structures
        if fcntl.ioctl(self.device_handle, HIDIOCINITREPORT, 0) < 0:
            raise SystemExit("FATAL: Failed to initialize internal report "
                             "structures")

        self.usage_ref = hiddev_usage_ref(report_type=HID_REPORT_TYPE_FEATURE,
                                          report_id=BRIGHTNESS_CONTROL,
                                          field_index=0, usage_index=0,
                                          usage_code=USAGE_CODE)

        self.rep_info = hiddev_report_info(report_type=HID_REPORT_TYPE_FEATURE,
                                           report_id=BRIGHTNESS_CONTROL,
                                           num_fields=1)



    def get_hid_driver_version(self):
        version = hid_version()
        fcntl.ioctl(self.device_handle, HIDIOCGVERSION, version)
        return version.v1, version.v2, version.v3

    def get_product_information(self):
        return {'product_id': self.product_id,
                'product_name': self.product_name,
                'vendor_id': self.vendor_id, 'vendor_name': self.vendor_name}

    def get_brightness(self):
        """Return the current brightness value.
         """

        if fcntl.ioctl(self.device_handle, HIDIOCGUSAGE, self.usage_ref) < 0:
            raise SystemExit("Get usage failed")

        if fcntl.ioctl(self.device_handle, HIDIOCGREPORT, self.rep_info) < 0:
            raise SystemExit("Get report failed")

        return int(self.usage_ref.value)

    def set_brightness(self, value):
        """Set the brightness value.
        """
        value = int(value)

        if self.clamp:
            lo, hi = self.clamp
            if value > hi or value < lo:
                print("Warning: value out of range [%d, %d), "
                      "clamping." % (lo, hi+1))
            value = max(lo, min(hi, value))

        self.usage_ref.value = value
        if fcntl.ioctl(self.device_handle, HIDIOCSUSAGE, self.usage_ref) < 0:
            raise SystemExit("Set usage failed")

        if fcntl.ioctl(self.device_handle, HIDIOCSREPORT, self.rep_info) < 0:
            raise SystemExit("Set report failed")

        return value

    def adjust_brightness(self, increment):
        """Apply a brightness adjustment relative to the current setting.
        Returns the old value and the current value
        """
        old = self.get_brightness()
        current = old + increment
        current = self.set_brightness(current)

        return old, current


def main():
    arg_parser = argparse.ArgumentParser(
        description='Set brightness on Apple and some other USB monitors.')
    arg_parser.add_argument('device', nargs='?', help='Path to the HID device')
    arg_parser.add_argument('brightness', nargs='?', default='',
                            help='New brightness level. If starts with +/-, '
                                 'it will be increased/decreased.')
    args = arg_parser.parse_args()

    if not args.device:
        arg_parser.print_help()
        sys.exit(1)

    try:
        monitor = AppleCinemaDisplay(args.device)
    except DeviceNotSupported as e:
        print(e)
        sys.exit(1)

    print('hiddev driver version: %d.%d.%d' % monitor.get_hid_driver_version())
    print('Found supported product 0x{product_id:04x} ({product_name}) of '
          'vendor 0x{vendor_id:04x} ({vendor_name})'
          ''.format(**monitor.get_product_information()))

    if not args.brightness:
        brightness = monitor.get_brightness()
        print("Current brightness level is", brightness,
              "(%.0f%%)" % (100 * brightness / 256))
        sys.exit(0)

    if args.brightness.startswith(('+', '-')):
        # increase/decrease brightness
        old, current = monitor.adjust_brightness(int(args.brightness))
        print("Adjusted brightness from", old, "by", args.brightness, "to",
              current)

    else:
        brightness = monitor.set_brightness(int(args.brightness))
        print("Brightness set to %d" % brightness)


if __name__ == '__main__':
    main()