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COMEDI - Linux Control and Measurement Device Interface
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Copyright (C) 1998 David A. Schleef <ds@schleef.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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Description: generic 8255 support
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Devices: [standard] 8255 (8255)
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Updated: Fri, 7 Jun 2002 12:56:45 -0700
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The classic in digital I/O. The 8255 appears in Comedi as a single
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digital I/O subdevice with 24 channels. The channel 0 corresponds
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to the 8255's port A, bit 0; channel 23 corresponds to port C, bit
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7. Direction configuration is done in blocks, with channels 0-7,
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8-15, 16-19, and 20-23 making up the 4 blocks. The only 8255 mode
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You should enable compilation this driver if you plan to use a board
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that has an 8255 chip. For multifunction boards, the main driver will
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configure the 8255 subdevice automatically.
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This driver also works independently with ISA and PCI cards that
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directly map the 8255 registers to I/O ports, including cards with
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multiple 8255 chips. To configure the driver for such a card, the
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option list should be a list of the I/O port bases for each of the
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8255 chips. For example,
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comedi_config /dev/comedi0 8255 0x200,0x204,0x208,0x20c
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Note that most PCI 8255 boards do NOT work with this driver, and
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need a separate driver as a wrapper. For those that do work, the
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I/O port base address can be found in the output of 'lspci -v'.
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This file contains an exported subdevice for driving an 8255.
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To use this subdevice as part of another driver, you need to
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set up the subdevice in the attach function of the driver by
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subdev_8255_init(device, subdevice, callback_function, arg)
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device and subdevice are pointers to the device and subdevice
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structures. callback_function will be called to provide the
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low-level input/output to the device, i.e., actual register
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access. callback_function will be called with the value of arg
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as the last parameter. If the 8255 device is mapped as 4
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consecutive I/O ports, you can use NULL for callback_function
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and the I/O port base for arg, and an internal function will
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handle the register access.
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In addition, if the main driver handles interrupts, you can
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enable commands on the subdevice by calling subdev_8255_init_irq()
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instead. Then, when you get an interrupt that is likely to be
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from the 8255, you should call subdev_8255_interrupt(), which
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will copy the latched value to a Comedi buffer.
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#include "../comedidev.h"
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#include <linux/ioport.h>
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#include <linux/slab.h>
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#define CR_C_LO_IO 0x01
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#define CR_B_MODE 0x04
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#define CR_C_HI_IO 0x08
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#define CR_A_MODE(a) ((a)<<5)
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struct subdev_8255_struct {
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unsigned long cb_arg;
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int (*cb_func) (int, int, int, unsigned long);
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#define CALLBACK_ARG (((struct subdev_8255_struct *)s->private)->cb_arg)
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#define CALLBACK_FUNC (((struct subdev_8255_struct *)s->private)->cb_func)
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#define subdevpriv ((struct subdev_8255_struct *)s->private)
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static int dev_8255_attach(struct comedi_device *dev,
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struct comedi_devconfig *it);
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static int dev_8255_detach(struct comedi_device *dev);
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static struct comedi_driver driver_8255 = {
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.driver_name = "8255",
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.module = THIS_MODULE,
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.attach = dev_8255_attach,
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.detach = dev_8255_detach,
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static int __init driver_8255_init_module(void)
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return comedi_driver_register(&driver_8255);
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static void __exit driver_8255_cleanup_module(void)
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comedi_driver_unregister(&driver_8255);
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module_init(driver_8255_init_module);
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module_exit(driver_8255_cleanup_module);
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static void do_config(struct comedi_device *dev, struct comedi_subdevice *s);
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void subdev_8255_interrupt(struct comedi_device *dev,
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struct comedi_subdevice *s)
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d = CALLBACK_FUNC(0, _8255_DATA, 0, CALLBACK_ARG);
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d |= (CALLBACK_FUNC(0, _8255_DATA + 1, 0, CALLBACK_ARG) << 8);
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comedi_buf_put(s->async, d);
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s->async->events |= COMEDI_CB_EOS;
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comedi_event(dev, s);
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EXPORT_SYMBOL(subdev_8255_interrupt);
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static int subdev_8255_cb(int dir, int port, int data, unsigned long arg)
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unsigned long iobase = arg;
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outb(data, iobase + port);
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return inb(iobase + port);
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static int subdev_8255_insn(struct comedi_device *dev,
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struct comedi_subdevice *s,
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struct comedi_insn *insn, unsigned int *data)
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s->state &= ~data[0];
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s->state |= (data[0] & data[1]);
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CALLBACK_FUNC(1, _8255_DATA, s->state & 0xff,
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if (data[0] & 0xff00)
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CALLBACK_FUNC(1, _8255_DATA + 1, (s->state >> 8) & 0xff,
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if (data[0] & 0xff0000)
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CALLBACK_FUNC(1, _8255_DATA + 2,
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(s->state >> 16) & 0xff, CALLBACK_ARG);
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data[1] = CALLBACK_FUNC(0, _8255_DATA, 0, CALLBACK_ARG);
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data[1] |= (CALLBACK_FUNC(0, _8255_DATA + 1, 0, CALLBACK_ARG) << 8);
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data[1] |= (CALLBACK_FUNC(0, _8255_DATA + 2, 0, CALLBACK_ARG) << 16);
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static int subdev_8255_insn_config(struct comedi_device *dev,
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struct comedi_subdevice *s,
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struct comedi_insn *insn, unsigned int *data)
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mask = 1 << CR_CHAN(insn->chanspec);
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else if (mask & 0x00ff00)
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else if (mask & 0x0f0000)
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case INSN_CONFIG_DIO_INPUT:
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case INSN_CONFIG_DIO_OUTPUT:
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case INSN_CONFIG_DIO_QUERY:
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data[1] = (s->io_bits & bits) ? COMEDI_OUTPUT : COMEDI_INPUT;
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static void do_config(struct comedi_device *dev, struct comedi_subdevice *s)
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/* 1 in io_bits indicates output, 1 in config indicates input */
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if (!(s->io_bits & 0x0000ff))
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if (!(s->io_bits & 0x00ff00))
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if (!(s->io_bits & 0x0f0000))
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config |= CR_C_LO_IO;
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if (!(s->io_bits & 0xf00000))
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config |= CR_C_HI_IO;
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CALLBACK_FUNC(1, _8255_CR, config, CALLBACK_ARG);
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static int subdev_8255_cmdtest(struct comedi_device *dev,
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struct comedi_subdevice *s,
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struct comedi_cmd *cmd)
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tmp = cmd->start_src;
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cmd->start_src &= TRIG_NOW;
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if (!cmd->start_src || tmp != cmd->start_src)
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tmp = cmd->scan_begin_src;
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cmd->scan_begin_src &= TRIG_EXT;
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if (!cmd->scan_begin_src || tmp != cmd->scan_begin_src)
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tmp = cmd->convert_src;
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cmd->convert_src &= TRIG_FOLLOW;
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if (!cmd->convert_src || tmp != cmd->convert_src)
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tmp = cmd->scan_end_src;
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cmd->scan_end_src &= TRIG_COUNT;
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if (!cmd->scan_end_src || tmp != cmd->scan_end_src)
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cmd->stop_src &= TRIG_NONE;
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if (!cmd->stop_src || tmp != cmd->stop_src)
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if (cmd->start_arg != 0) {
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if (cmd->scan_begin_arg != 0) {
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cmd->scan_begin_arg = 0;
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if (cmd->convert_arg != 0) {
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cmd->convert_arg = 0;
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if (cmd->scan_end_arg != 1) {
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cmd->scan_end_arg = 1;
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if (cmd->stop_arg != 0) {
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static int subdev_8255_cmd(struct comedi_device *dev,
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struct comedi_subdevice *s)
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static int subdev_8255_cancel(struct comedi_device *dev,
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struct comedi_subdevice *s)
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int subdev_8255_init(struct comedi_device *dev, struct comedi_subdevice *s,
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int (*cb) (int, int, int, unsigned long),
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s->type = COMEDI_SUBD_DIO;
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s->subdev_flags = SDF_READABLE | SDF_WRITABLE;
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s->range_table = &range_digital;
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s->private = kmalloc(sizeof(struct subdev_8255_struct), GFP_KERNEL);
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CALLBACK_FUNC = subdev_8255_cb;
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s->insn_bits = subdev_8255_insn;
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s->insn_config = subdev_8255_insn_config;
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EXPORT_SYMBOL(subdev_8255_init);
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int subdev_8255_init_irq(struct comedi_device *dev, struct comedi_subdevice *s,
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int (*cb) (int, int, int, unsigned long),
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ret = subdev_8255_init(dev, s, cb, arg);
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s->do_cmdtest = subdev_8255_cmdtest;
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s->do_cmd = subdev_8255_cmd;
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s->cancel = subdev_8255_cancel;
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subdevpriv->have_irq = 1;
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EXPORT_SYMBOL(subdev_8255_init_irq);
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void subdev_8255_cleanup(struct comedi_device *dev, struct comedi_subdevice *s)
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EXPORT_SYMBOL(subdev_8255_cleanup);
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Start of the 8255 standalone device
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static int dev_8255_attach(struct comedi_device *dev,
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struct comedi_devconfig *it)
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unsigned long iobase;
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dev->board_name = "8255";
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for (i = 0; i < COMEDI_NDEVCONFOPTS; i++) {
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iobase = it->options[i];
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"comedi%d: 8255: no devices specified\n", dev->minor);
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ret = alloc_subdevices(dev, i);
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/* FIXME this printk call should give a proper message, the
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* below line just maintains previous functionality */
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printk("comedi%d: 8255:", dev->minor);
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printk(KERN_INFO "comedi%d: 8255:", dev->minor);
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for (i = 0; i < dev->n_subdevices; i++) {
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iobase = it->options[i];
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printk(" 0x%04lx", iobase);
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if (!request_region(iobase, _8255_SIZE, "8255")) {
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printk(" (I/O port conflict)");
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dev->subdevices[i].type = COMEDI_SUBD_UNUSED;
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subdev_8255_init(dev, dev->subdevices + i, NULL,
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static int dev_8255_detach(struct comedi_device *dev)
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unsigned long iobase;
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struct comedi_subdevice *s;
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printk(KERN_INFO "comedi%d: 8255: remove\n", dev->minor);
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for (i = 0; i < dev->n_subdevices; i++) {
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s = dev->subdevices + i;
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if (s->type != COMEDI_SUBD_UNUSED) {
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iobase = CALLBACK_ARG;
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release_region(iobase, _8255_SIZE);
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subdev_8255_cleanup(dev, s);
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MODULE_AUTHOR("Comedi http://www.comedi.org");
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MODULE_DESCRIPTION("Comedi low-level driver");
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MODULE_LICENSE("GPL");