ds2482: i2c to 1-wire bridge

This patch adds support for the Maxim DS2482-100 and DS2482-800 chips, which are i2c devices that provide 1 or 8 1-wire masters.

I put the code under drivers/i2c/chips, but perhaps it should go under drivers/w1.

Signed-off-by Ben Gardner <[email protected]>

 drivers/i2c/chips/Kconfig  |   12 
 drivers/i2c/chips/Makefile |    1 
 drivers/i2c/chips/ds2482.c |  557 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 570 insertions(+)

Index: linux-2.6.15-rc3-mm1/drivers/i2c/chips/Makefile =================================> --- linux-2.6.15-rc3-mm1.orig/drivers/i2c/chips/Makefile +++ linux-2.6.15-rc3-mm1/drivers/i2c/chips/Makefile

(quoted diff) +1 -0

@@ -12,6 +12,7 @@ obj-$(CONFIG_SENSORS_PCF8574)	+= pcf8574
 obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o
 obj-$(CONFIG_SENSORS_RTC8564)	+= rtc8564.o
 obj-$(CONFIG_ISP1301_OMAP)	+= isp1301_omap.o
+obj-$(CONFIG_SENSORS_DS2482)	+= ds2482.o
 obj-$(CONFIG_TPS65010)		+= tps65010.o
 obj-$(CONFIG_RTC_X1205_I2C)	+= x1205.o
 

Index: linux-2.6.15-rc3-mm1/drivers/i2c/chips/ds2482.c =================================> --- /dev/null +++ linux-2.6.15-rc3-mm1/drivers/i2c/chips/ds2482.c

(quoted diff) +39 -0

@@ -0,0 +1,557 @@
+/**
+ * ds2482.c - provides i2c to w1-master bridge(s)
+ * Copyright (C) 2005  Ben Gardner <[email protected]>
+ *
+ * The DS2482 is a sensor chip made by Dallis Semiconductor (Maxim).
+ * It is a I2C to 1-wire bridge.
+ * There are two variations: -100 and -800, which have 1 or 8 1-wire ports.
+ * The complete datasheet can be obtained from MAXIM's website at:
+ *   http://www.maxim-ic.com
+ *
+ * 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 of the License.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <asm/delay.h>
+
+#include "../../w1/w1.h"
+#include "../../w1/w1_int.h"
+
+/**
+ * Address is selected using 2 pins, resulting in 4 possible addresses.
+ *  0x18, 0x19, 0x1a, 0x1b
+ * However, this chip is rare and should not be detected, so use the force
+ * module parameter.
+ */
+static unsigned short normal_i2c[] = {I2C_CLIENT_END};
+
+/**
+ * Insmod parameters
+ */
+I2C_CLIENT_INSMOD_1(ds2482);
+
+/**
+ * The DS2482 registers - there are 3 registers that are addressed by a read

(quoted diff) +84 -0

+#define DS2482_CMD_CHANNEL_SELECT      0xC3	/* Param: Channel byte - DS2482-800 only */
+#define DS2482_CMD_WRITE_CONFIG        0xD2	/* Param: Config byte */
+#define DS2482_CMD_1WIRE_RESET         0xB4	/* Param: None */
+#define DS2482_CMD_1WIRE_SINGLE_BIT    0x87	/* Param: Bit byte (bit7) */
+#define DS2482_CMD_1WIRE_WRITE_BYTE    0xA5	/* Param: Data byte */
+#define DS2482_CMD_1WIRE_READ_BYTE     0x96	/* Param: None */
+/* Note to read the byte, Set the ReadPtr to Data then read (any addr) */
+#define DS2482_CMD_1WIRE_TRIPLET       0x78	/* Param: Dir byte (bit7) */
+
+/**
+ * Configure Register bit definitions
+ * The top 4 bits always read 0.
+ * To write, the top nibble must be the 1's compl. of the low nibble.
+ */
+#define DS2482_REG_CFG_1WS             0x08
+#define DS2482_REG_CFG_SPU             0x04
+#define DS2482_REG_CFG_PPM             0x02
+#define DS2482_REG_CFG_APU             0x01
+
+/* Write and verify codes for the CHANNEL_SELECT command (DS2482-800 only) */
+static u8 ds2482_chan_wr[8] = { 0xF0, 0xE1, 0xD2, 0xC3, 0xB4, 0xA5, 0x96, 0x87};
+static u8 ds2482_chan_rd[8] = { 0xB8, 0xB1, 0xAA, 0xA3, 0x9C, 0x95, 0x8E, 0x87};
+
+
+/**
+ * Status Register bit definitions (read only)
+ */
+#define DS2482_REG_STS_DIR             0x80
+#define DS2482_REG_STS_TSB             0x40
+#define DS2482_REG_STS_SBR             0x20
+#define DS2482_REG_STS_RST             0x10
+#define DS2482_REG_STS_LL              0x08
+#define DS2482_REG_STS_SD              0x04
+#define DS2482_REG_STS_PPD             0x02
+#define DS2482_REG_STS_1WB             0x01
+
+
+static int ds2482_attach_adapter(struct i2c_adapter *adapter);
+static int ds2482_detect(struct i2c_adapter *adapter, int address, int kind);
+static int ds2482_detach_client(struct i2c_client *client);
+
+
+/**
+ * Driver data (common to all clients)
+ */
+static struct i2c_driver ds2482_driver = {
+	.owner		= THIS_MODULE,
+	.name		= "ds2482",
+	.flags		= I2C_DF_NOTIFY,
+	.attach_adapter	= ds2482_attach_adapter,
+	.detach_client	= ds2482_detach_client,
+};
+
+/*
+ * Client data (each client gets its own)
+ */
+
+struct ds2482_data;
+
+struct ds2482_w1_chan {
+	struct ds2482_data	*pdev;
+	u8			channel;
+	struct w1_bus_master	w1_bus_master;
+};
+
+struct ds2482_data {
+	struct i2c_client	client;
+	struct semaphore	access_lock;
+
+	/* 1-wire interface(s) */
+	int			w1_count;	/* 1 or 8 */
+	struct ds2482_w1_chan	w1_ch[8];
+
+	/* per-device values */
+	u8			channel;
+	u8			read_prt;	/* see DS2482_PTR_CODE_xxx */
+	u8			reg_config;
+};
+
+
+/**
+ * Sets the read pointer.
+ * @param pdev       The ds2482 client pointer
+ * @param read_ptr   see DS2482_PTR_CODE_xxx above

(quoted diff) +55 -0

+		pdev->read_prt = read_ptr;
+	}
+	return(0);
+}
+
+/**
+ * Sends a command without a parameter
+ * @param pdev       The ds2482 client pointer
+ * @param cmd        DS2482_CMD_RESET,
+ *                   DS2482_CMD_1WIRE_RESET,
+ *                   DS2482_CMD_1WIRE_READ_BYTE
+ * @return -1 on failure, 0 on success
+ */
+static inline int ds2482_send_cmd(struct ds2482_data *pdev, u8 cmd)
+{
+	if ( i2c_smbus_write_byte(&pdev->client, cmd) < 0 ) {
+		return(-1);
+	}
+	pdev->read_prt = DS2482_PTR_CODE_STATUS;
+	return(0);
+}
+
+/**
+ * Sends a command with a parameter
+ * @param pdev       The ds2482 client pointer
+ * @param cmd        DS2482_CMD_WRITE_CONFIG,
+ *                   DS2482_CMD_1WIRE_SINGLE_BIT,
+ *                   DS2482_CMD_1WIRE_WRITE_BYTE,
+ *                   DS2482_CMD_1WIRE_TRIPLET
+ * @param byte       The data to send
+ * @return -1 on failure, 0 on success
+ */
+static inline int ds2482_send_cmd_data(struct ds2482_data *pdev, u8 cmd, u8 byte)
+{
+	if ( i2c_smbus_write_byte_data(&pdev->client, cmd, byte) < 0 ) {
+		return(-1);
+	}
+	/* all cmds leave in STATUS, except CONFIG */
+	pdev->read_prt = (cmd != DS2482_CMD_WRITE_CONFIG) ?
+			 DS2482_PTR_CODE_STATUS : DS2482_PTR_CODE_CONFIG;
+	return(0);
+}
+
+
+/*
+ * 1-Wire interface code
+ */
+
+
+/**
+ * Waits until the 1-wire interface is idle (not busy)
+ *
+ * @param pdev Pointer to the device structure
+ * @return the last value read from status or -1 (failure)
+ */

(quoted diff) +348 -0

+/**
+ * Selects a w1 channel.
+ * The 1-wire interface must be idle before calling this function.
+ *
+ * @param pdev       The ds2482 client pointer
+ * @param channel    0-7
+ * @return           -1 (failure) or 0 (success)
+ */
+static inline int ds2482_set_channel(struct ds2482_data *pdev, u8 channel)
+{
+	if (channel >= 8)
+		return -1;
+
+	if ( i2c_smbus_write_byte_data(&pdev->client, DS2482_CMD_CHANNEL_SELECT,
+				       ds2482_chan_wr[channel]) < 0 )
+		return -1;
+
+	pdev->read_prt = DS2482_PTR_CODE_CHANNEL;
+	pdev->channel = -1;
+	if (i2c_smbus_read_byte(&pdev->client) = ds2482_chan_rd[channel]) {
+		pdev->channel = channel;
+		return 0;
+	}
+	return -1;
+}
+
+
+/**
+ * Performs the touch-bit function, which writes a 0 or 1 and reads the level.
+ *
+ * @param data       The ds2482 channel pointer
+ * @param bit        The level to write: 0 or non-zero
+ * @return           The level read: 0 or 1
+ */
+static u8 ds2482_w1_touch_bit(unsigned long data, u8 bit)
+{
+	struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;
+	struct ds2482_data    *pdev = pchan->pdev;
+	int status = -1;
+
+	down(&pdev->access_lock);
+
+	/* Select the channel */
+	ds2482_wait_1wire_idle(pdev);
+	if (pdev->w1_count > 1) {
+		ds2482_set_channel(pdev, pchan->channel);
+	}
+
+	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_SINGLE_BIT,
+                                  bit ? 0xFF : 0)) {
+		/* Wait until 1WB = 0, return the status */
+		status = ds2482_wait_1wire_idle(pdev);
+	}
+	up(&pdev->access_lock);
+
+	return((status & DS2482_REG_STS_SBR) ? 1 : 0);
+}
+
+/**
+ * Performs the triplet function, which reads two bits and writes a bit.
+ * The bit written is determined by the two reads:
+ *   00 => dbit, 01 => 0, 10 => 1
+ *
+ * @param data       The ds2482 channel pointer
+ * @param dbit       The direction to choose if both branches are valid
+ * @return           b0=read1 b1=read2 b3=bit written
+ */
+static u8 ds2482_w1_triplet(unsigned long data, u8 dbit)
+{
+	struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;
+	struct ds2482_data    *pdev = pchan->pdev;
+	int status=3, result;
+
+	down(&pdev->access_lock);
+
+	/* Select the channel */
+	ds2482_wait_1wire_idle(pdev);
+	if (pdev->w1_count > 1) {
+		ds2482_set_channel(pdev, pchan->channel);
+	}
+
+	/* Send the triplet command */
+	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_TRIPLET,
+                                  dbit ? 0xFF : 0)) {
+		/* Wait until 1WB = 0, grab the status */
+		status = ds2482_wait_1wire_idle(pdev);
+	}
+	up(&pdev->access_lock);
+
+	/* Decode the status */
+	result = (status >> 5);
+	return(result);
+}
+
+/**
+ * Performs the write byte function.
+ *
+ * @param data       The ds2482 channel pointer
+ * @param byte       The value to write
+ */
+static void ds2482_w1_write_byte(unsigned long data, u8 byte)
+{
+	struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;
+	struct ds2482_data    *pdev = pchan->pdev;
+
+	down(&pdev->access_lock);
+
+	/* Select the channel */
+	ds2482_wait_1wire_idle(pdev);
+	if (pdev->w1_count > 1) {
+		ds2482_set_channel(pdev, pchan->channel);
+	}
+
+	/* Send the write byte command */
+	ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_WRITE_BYTE, byte);
+
+	up(&pdev->access_lock);
+}
+
+/**
+ * Performs the read byte function.
+ *
+ * @param data       The ds2482 channel pointer
+ * @return           The value read
+ */
+static u8 ds2482_w1_read_byte(unsigned long data)
+{
+	struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;
+	struct ds2482_data    *pdev = pchan->pdev;
+	int result;
+
+	down(&pdev->access_lock);
+
+	/* Select the channel */
+	ds2482_wait_1wire_idle(pdev);
+	if (pdev->w1_count > 1) {
+		ds2482_set_channel(pdev, pchan->channel);
+	}
+
+	/* Send the read byte command */
+	ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_READ_BYTE);
+
+	/* Wait until 1WB = 0 */
+	ds2482_wait_1wire_idle(pdev);
+
+	/* Select the data register */
+	ds2482_select_register(pdev, DS2482_PTR_CODE_DATA);
+
+	/* Read the data byte */
+	result = i2c_smbus_read_byte(&pdev->client);
+
+	up(&pdev->access_lock);
+
+	return((u8)result);
+}
+
+
+/**
+ * Sends a reset on the 1-wire interface
+ *
+ * @param data    The ds2482 channel pointer
+ * @return        0Þvice present, 1=No device present or error
+ */
+static u8 ds2482_w1_reset_bus(unsigned long data)
+{
+	struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;
+	struct ds2482_data    *pdev = pchan->pdev;
+	int err;
+	u8 retval = 1;
+
+	down(&pdev->access_lock);
+
+	/* Select the channel */
+	ds2482_wait_1wire_idle(pdev);
+	if (pdev->w1_count > 1) {
+		ds2482_set_channel(pdev, pchan->channel);
+	}
+
+	/* Send the reset command */
+	err = ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_RESET);
+	if (err >= 0) {
+		/* Wait until the reset is complete */
+		err = ds2482_wait_1wire_idle(pdev);
+		retval = (err & DS2482_REG_STS_PPD) ? 0 : 1;
+
+		/* If the chip did reset since detect, re-config it */
+		if (err & DS2482_REG_STS_RST) {
+			ds2482_send_cmd_data(pdev, DS2482_CMD_WRITE_CONFIG,
+                                             0xF0);
+		}
+	}
+
+	up(&pdev->access_lock);
+
+	return(retval);
+}
+
+
+/**
+ * Called to see if the device exists on an i2c bus.
+ */
+static int ds2482_attach_adapter(struct i2c_adapter *adapter)
+{
+	return(i2c_probe(adapter, &addr_data, ds2482_detect));
+}
+
+
+/*
+ * The following function does more than just detection. If detection
+ * succeeds, it also registers the new chip.
+ */
+static int ds2482_detect(struct i2c_adapter *adapter, int address, int kind)
+{
+	struct ds2482_data *data;
+	struct i2c_client  *new_client;
+	int err = 0;
+	int temp1;
+	int idx;
+
+	if ( !i2c_check_functionality(adapter,
+				      I2C_FUNC_SMBUS_BYTE_DATA |
+				      I2C_FUNC_SMBUS_BYTE) ) {
+		goto exit;
+	}
+
+	if ( !(data = kmalloc(sizeof(struct ds2482_data), GFP_KERNEL)) ) {
+		err = -ENOMEM;
+		goto exit;
+	}
+	memset(data, 0, sizeof(struct ds2482_data));
+
+	new_client = &data->client;
+	i2c_set_clientdata(new_client, data);
+	new_client->addr = address;
+	new_client->adapter = adapter;
+	new_client->driver = &ds2482_driver;
+	new_client->flags = 0;
+
+	/* Reset the device (sets the read_ptr to status) */
+	if ( ds2482_send_cmd(data, DS2482_CMD_RESET) < 0 ) {
+		dev_dbg(&adapter->dev, "DS2482 reset failed at 0x%02x.\n",
+			address);
+		goto exit_free;
+	}
+
+	/* Sleep at least 525ns to allow the reset to complete */
+	ndelay(525);
+
+	/* Read the status byte - expect reset bit and line to be set */
+	temp1 = i2c_smbus_read_byte(new_client);
+	if (temp1 != (DS2482_REG_STS_LL | DS2482_REG_STS_RST)) {
+		dev_dbg(&adapter->dev, "DS2482 (0x%02x) reset status "
+			"0x%02X - not a DS2482\n", address, temp1);
+		goto exit_free;
+	}
+
+	/* Detect the 8-port version */
+	data->w1_count = 1;
+	if (ds2482_set_channel(data, 7) = 0) {
+		data->w1_count = 8;
+	}
+
+	/* Set all config items to 0 (off) */
+	ds2482_send_cmd_data(data, DS2482_CMD_WRITE_CONFIG, 0xF0);
+
+	/* We can fill in the remaining client fields */
+	sprintf(new_client->name, "ds2482-%d00", data->w1_count);
+
+	init_MUTEX(&data->access_lock);
+
+	/* Tell the I2C layer a new client has arrived */
+	if ( (err = i2c_attach_client(new_client)) )
+		goto exit_free;
+
+	/* Register 1-wire interface(s) */
+	for (idx = 0; idx < data->w1_count; idx++) {
+		data->w1_ch[idx].pdev = data;
+		data->w1_ch[idx].channel = idx;
+
+		/* Populate all the w1 bus master stuff */
+		data->w1_ch[idx].w1_bus_master.data = (unsigned long)&data->w1_ch[idx];
+		data->w1_ch[idx].w1_bus_master.read_byte  = ds2482_w1_read_byte;
+		data->w1_ch[idx].w1_bus_master.write_byte = ds2482_w1_write_byte;
+		data->w1_ch[idx].w1_bus_master.touch_bit  = ds2482_w1_touch_bit;
+		data->w1_ch[idx].w1_bus_master.triplet    = ds2482_w1_triplet;
+		data->w1_ch[idx].w1_bus_master.reset_bus  = ds2482_w1_reset_bus;
+
+		err = w1_add_master_device(&data->w1_ch[idx].w1_bus_master);
+		if ( err ) {
+			data->w1_ch[idx].pdev = NULL;
+			goto exit_w1_remove;
+		}
+	}
+
+	return(0);
+
+exit_w1_remove:
+	for (idx = 0; idx < data->w1_count; idx++) {
+		if (data->w1_ch[idx].pdev != NULL) {
+			w1_remove_master_device(&data->w1_ch[idx].w1_bus_master);
+		}
+	}
+exit_free:
+	kfree(data);
+exit:
+	return(err);
+}
+
+static int ds2482_detach_client(struct i2c_client *client)
+{
+	struct ds2482_data   *data = i2c_get_clientdata(client);
+	int err, idx;
+
+	/* Unregister the 1-wire bridge(s) */
+	for (idx = 0; idx < data->w1_count; idx++) {
+		if (data->w1_ch[idx].pdev != NULL) {
+			w1_remove_master_device(&data->w1_ch[idx].w1_bus_master);
+		}
+	}
+
+	/* Detach the i2c device */
+	if ( (err = i2c_detach_client(client)) ) {
+		dev_err(&client->dev,
+			"Client deregistration failed, client not detached.\n");
+		return(err);
+	}
+
+	/* Free the memory */
+	kfree(data);
+	return(0);
+}
+
+static int __init sensors_ds2482_init(void)
+{
+	return(i2c_add_driver(&ds2482_driver));
+}
+
+static void __exit sensors_ds2482_exit(void)
+{
+	i2c_del_driver(&ds2482_driver);
+}
+
+MODULE_AUTHOR("Ben Gardner <[email protected]>");
+MODULE_DESCRIPTION("DS2482 driver");
+MODULE_LICENSE("GPL");
+
+module_init(sensors_ds2482_init);
+module_exit(sensors_ds2482_exit);

Index: linux-2.6.15-rc3-mm1/drivers/i2c/chips/Kconfig =================================> --- linux-2.6.15-rc3-mm1.orig/drivers/i2c/chips/Kconfig +++ linux-2.6.15-rc3-mm1/drivers/i2c/chips/Kconfig

(quoted diff) +8 -0

+	help
+	  If you say yes here you get support for the Maxim DS2482
+	  I2C to 1-Wire bridge.
+	  This, obviously, requires the 1-Wire subsystem (W1)
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called ds2482.
+
 endmenu

This patch adds support for the Maxim DS2482-100 and DS2482-800 chips, which are i2c devices that provide 1 or 8 1-wire masters.

I put the code under drivers/i2c/chips, but perhaps it should go under drivers/w1.

+ * The DS2482 is a sensor chip made by Dallis Semiconductor (Maxim).

+ * The complete datasheet can be obtained from MAXIM's website at:
+ * http://www.maxim-ic.com

+/**
+ * Address is selected using 2 pins, resulting in 4 possible addresses.
+ * 0x18, 0x19, 0x1a, 0x1b
+ * However, this chip is rare and should not be detected, so use the force
+ * module parameter.
+ */

Review

Quoted 3 lines

(quoted diff) +3 -0

+static u8 ds2482_w1_touch_bit(unsigned long data, u8 bit)
+{
+     struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;

That's an ugly cast. Can't it be avoided?

If there aren't any objections, I'll follow the i2c layout and create a drivers/w1/busses folder and put the driver there.
Should I also create a few patches to move the matrox_w1 and ds_w1_bridge stuff to that folder?
Should I also create a drivers/w1/chips folder and move the family drivers?

Quoted 5 lines

Review

Quoted 3 lines

(quoted diff) +3 -0

+static u8 ds2482_w1_touch_bit(unsigned long data, u8 bit)
+{
+     struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;

That's an ugly cast. Can't it be avoided?

Sure, if we change the w1 subsystem to use 'void *' as the user-data type instead of 'unsigned long'.
Eugeniy - are you OK with that change?

Thanks,
Ben

Quoted 5 lines · Ben Gardner (gardner.ben at gmail.com)

If there aren't any objections, I'll follow the i2c layout and create a drivers/w1/busses folder and put the driver there.
Should I also create a few patches to move the matrox_w1 and ds_w1_bridge stuff to that folder?
Should I also create a drivers/w1/chips folder and move the family drivers?

Hmm, any other names? There are no at least busses in the w1 world. Maybe masters/bus_masters/controllers/something...?

Quoted 9 lines

Quoted 5 lines

Review

Quoted 3 lines

(quoted diff) +3 -0

+static u8 ds2482_w1_touch_bit(unsigned long data, u8 bit)
+{
+     struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;

That's an ugly cast. Can't it be avoided?

Sure, if we change the w1 subsystem to use 'void *' as the user-data type instead of 'unsigned long'.
Eugeniy - are you OK with that change?

No problem, but make it in a separate patch.

Quoted 2 lines

Thanks,
Ben

--
Evgeniy Polyakov

It seems that most w1 documentation refers to them as masters and slaves, so how about:
drivers/w1/masters
drivers/w1/slaves

I'll create three patch series:
- change 'unsigned long' to 'void *'
- move master and slave code into subfolders
- add ds2482

Does that sound OK?

Thanks,
Ben

Quoted 28 lines · Evgeniy Polyakov

Quoted 5 lines · Ben Gardner (gardner.ben at gmail.com)

If there aren't any objections, I'll follow the i2c layout and create a drivers/w1/busses folder and put the driver there.
Should I also create a few patches to move the matrox_w1 and ds_w1_bridge stuff to that folder?
Should I also create a drivers/w1/chips folder and move the family drivers?

Hmm, any other names? There are no at least busses in the w1 world. Maybe masters/bus_masters/controllers/something...?

Quoted 9 lines

Quoted 5 lines

Review

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(quoted diff) +3 -0

+static u8 ds2482_w1_touch_bit(unsigned long data, u8 bit)
+{
+     struct ds2482_w1_chan *pchan = (struct ds2482_w1_chan *)data;

That's an ugly cast. Can't it be avoided?

Sure, if we change the w1 subsystem to use 'void *' as the user-data type instead of 'unsigned long'.
Eugeniy - are you OK with that change?

No problem, but make it in a separate patch.

Quoted 2 lines

Thanks,
Ben

--
Evgeniy Polyakov