add w1_ds28e17 driver for the DS28E17 Onewire to I2C master bridge

This subpatch adds a driver for the DS28E17 Onewire to I2C master bridge.

Signed-off-by: Jan Kandziora <jjj@gmx.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

6 files changed, 878 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-w1_ds28e17 b/Documentation/ABI/testing/sysfs-driver-w1_ds28e17
new file mode 100644
index 000000000000..d301e7017afe
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-w1_ds28e17
@@ -0,0 +1,21 @@
+What:           /sys/bus/w1/devices/19-<id>/speed
+Date:           Sep 2017
+KernelVersion:  4.14
+Contact:        Jan Kandziora <jjj@gmx.de>
+Description:    When written, this file sets the I2C speed on the connected
+                DS28E17 chip. When read, it reads the current setting from
+                the DS28E17 chip.
+                Valid values: 100, 400, 900 [kBaud].
+                Default 100, can be set by w1_ds28e17.speed= module parameter.
+Users:          w1_ds28e17 driver
+
+What:           /sys/bus/w1/devices/19-<id>/stretch
+Date:           Sep 2017
+KernelVersion:  4.14
+Contact:        Jan Kandziora <jjj@gmx.de>
+Description:    When written, this file sets the multiplier used to calculate
+                the busy timeout for I2C operations on the connected DS28E17
+                chip. When read, returns the current setting.
+                Valid values: 1 to 9.
+                Default 1, can be set by w1_ds28e17.stretch= module parameter.
+Users:          w1_ds28e17 driver
diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX
index 8d76718e1ea2..68946f83e579 100644
--- a/Documentation/w1/slaves/00-INDEX
+++ b/Documentation/w1/slaves/00-INDEX
@@ -10,3 +10,5 @@ w1_ds2438
         - The Maxim/Dallas Semiconductor ds2438 smart battery monitor.
 w1_ds28e04
         - The Maxim/Dallas Semiconductor ds28e04 eeprom.
+w1_ds28e17
+        - The Maxim/Dallas Semiconductor ds28e17 1-Wire-to-I2C Master Bridge.
diff --git a/Documentation/w1/slaves/w1_ds28e17 b/Documentation/w1/slaves/w1_ds28e17
new file mode 100644
index 000000000000..7fcfad5b4a37
--- /dev/null
+++ b/Documentation/w1/slaves/w1_ds28e17
@@ -0,0 +1,68 @@
+Kernel driver w1_ds28e17
+========================
+
+Supported chips:
+  * Maxim DS28E17 1-Wire-to-I2C Master Bridge
+
+supported family codes:
+        W1_FAMILY_DS28E17  0x19
+
+Author: Jan Kandziora <jjj@gmx.de>
+
+
+Description
+-----------
+The DS28E17 is a Onewire slave device which acts as an I2C bus master.
+
+This driver creates a new I2C bus for any DS28E17 device detected. I2C buses
+come and go as the DS28E17 devices come and go. I2C slave devices connected to
+a DS28E17 can be accessed by the kernel or userspace tools as if they were
+connected to a "native" I2C bus master.
+
+
+An udev rule like the following
+-------------------------------------------------------------------------------
+SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
+        SYMLINK+="i2c-$attr{name}"
+-------------------------------------------------------------------------------
+may be used to create stable /dev/i2c- entries based on the unique id of the
+DS28E17 chip.
+
+
+Driver parameters are:
+
+speed:
+        This sets up the default I2C speed a DS28E17 get configured for as soon
+        it is connected. The power-on default   of the DS28E17 is 400kBaud, but
+        chips may come and go on the Onewire bus without being de-powered and
+        as soon the "w1_ds28e17" driver notices a freshly connected, or
+        reconnected DS28E17 device on the Onewire bus, it will re-apply this
+        setting.
+
+        Valid values are 100, 400, 900 [kBaud]. Any other value means to leave
+        alone the current DS28E17 setting on detect. The default value is 100.
+
+stretch:
+        This sets up the default stretch value used for freshly connected
+        DS28E17 devices. It is a multiplier used on the calculation of the busy
+        wait time for an I2C transfer. This is to account for I2C slave devices
+        which make heavy use of the I2C clock stretching feature and thus, the
+        needed timeout cannot be pre-calculated correctly. As the w1_ds28e17
+        driver checks the DS28E17's busy flag in a loop after the precalculated
+        wait time, it should be hardly needed to tweak this setting.
+
+        Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
+        19-00000002dbd8: busy timeout" in the kernel log.
+
+        Valid values are 1 to 9. The default is 1.
+
+
+The driver creates sysfs files /sys/bus/w1/devices/19-<id>/speed and
+/sys/bus/w1/devices/19-<id>/stretch for each device, preloaded with the default
+settings from the driver parameters. They may be changed anytime. In addition a
+directory /sys/bus/w1/devices/19-<id>/i2c-<nnn> for the I2C bus master sysfs
+structure is created.
+
+
+See https://github.com/ianka/w1_ds28e17 for even more information.
+
diff --git a/drivers/w1/slaves/Kconfig b/drivers/w1/slaves/Kconfig
index 3c945f9f5f0f..7931231d8e80 100644
--- a/drivers/w1/slaves/Kconfig
+++ b/drivers/w1/slaves/Kconfig
@@ -148,4 +148,19 @@ config W1_SLAVE_DS28E04
 
           If you are unsure, say N.
 
+config W1_SLAVE_DS28E17
+        tristate "1-wire-to-I2C master bridge (DS28E17)"
+        select CRC16
+        depends on I2C
+        help
+          Say Y here if you want to use the DS28E17 1-wire-to-I2C master bridge.
+          For each DS28E17 detected, a new I2C adapter is created within the
+          kernel. I2C devices on that bus can be configured to be used by the
+          kernel and userspace tools as on any other "native" I2C bus.
+
+          This driver is also available as a module. If so, the module
+          will be called w1_ds28e17.
+
+          If you are unsure, say N.
+
 endmenu
diff --git a/drivers/w1/slaves/Makefile b/drivers/w1/slaves/Makefile
index 36b22fb2d3a1..855371a99e6a 100644
--- a/drivers/w1/slaves/Makefile
+++ b/drivers/w1/slaves/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_W1_SLAVE_DS2760)	+= w1_ds2760.o
 obj-$(CONFIG_W1_SLAVE_DS2780)   += w1_ds2780.o
 obj-$(CONFIG_W1_SLAVE_DS2781)   += w1_ds2781.o
 obj-$(CONFIG_W1_SLAVE_DS28E04)  += w1_ds28e04.o
+obj-$(CONFIG_W1_SLAVE_DS28E17)  += w1_ds28e17.o
diff --git a/drivers/w1/slaves/w1_ds28e17.c b/drivers/w1/slaves/w1_ds28e17.c
new file mode 100644
index 000000000000..e78b63ea4daf
--- /dev/null
+++ b/drivers/w1/slaves/w1_ds28e17.c
@@ -0,0 +1,771 @@
+/*
+ *      w1_ds28e17.c - w1 family 19 (DS28E17) driver
+ *
+ * Copyright (c) 2016 Jan Kandziora <jjj@gmx.de>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#include <linux/crc16.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+
+#define CRC16_INIT 0
+
+#include <linux/w1.h>
+
+#define W1_FAMILY_DS28E17 0x19
+
+/* Module setup. */
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Jan Kandziora <jjj@gmx.de>");
+MODULE_DESCRIPTION("w1 family 19 driver for DS28E17, 1-wire to I2C master bridge");
+MODULE_ALIAS("w1-family-" __stringify(W1_FAMILY_DS28E17));
+
+
+/* Default I2C speed to be set when a DS28E17 is detected. */
+static int i2c_speed = 100;
+module_param_named(speed, i2c_speed, int, (S_IRUSR | S_IWUSR));
+MODULE_PARM_DESC(speed, "Default I2C speed to be set when a DS28E17 is detected");
+
+/* Default I2C stretch value to be set when a DS28E17 is detected. */
+static char i2c_stretch = 1;
+module_param_named(stretch, i2c_stretch, byte, (S_IRUSR | S_IWUSR));
+MODULE_PARM_DESC(stretch, "Default I2C stretch value to be set when a DS28E17 is detected");
+
+/* DS28E17 device command codes. */
+#define W1_F19_WRITE_DATA_WITH_STOP      0x4B
+#define W1_F19_WRITE_DATA_NO_STOP        0x5A
+#define W1_F19_WRITE_DATA_ONLY           0x69
+#define W1_F19_WRITE_DATA_ONLY_WITH_STOP 0x78
+#define W1_F19_READ_DATA_WITH_STOP       0x87
+#define W1_F19_WRITE_READ_DATA_WITH_STOP 0x2D
+#define W1_F19_WRITE_CONFIGURATION       0xD2
+#define W1_F19_READ_CONFIGURATION        0xE1
+#define W1_F19_ENABLE_SLEEP_MODE         0x1E
+#define W1_F19_READ_DEVICE_REVISION      0xC4
+
+/* DS28E17 status bits */
+#define W1_F19_STATUS_CRC     0x01
+#define W1_F19_STATUS_ADDRESS 0x02
+#define W1_F19_STATUS_START   0x08
+
+/*
+ * Maximum number of I2C bytes to transfer within one CRC16 protected onewire
+ * command.
+ * */
+#define W1_F19_WRITE_DATA_LIMIT 255
+
+/* Maximum number of I2C bytes to read with one onewire command. */
+#define W1_F19_READ_DATA_LIMIT 255
+
+/* Constants for calculating the busy sleep. */
+#define W1_F19_BUSY_TIMEBASES { 90, 23, 10 }
+#define W1_F19_BUSY_GRATUITY  1000
+
+/* Number of checks for the busy flag before timeout. */
+#define W1_F19_BUSY_CHECKS 1000
+
+
+/* Slave specific data. */
+struct w1_f19_data {
+        u8 speed;
+        u8 stretch;
+        struct i2c_adapter adapter;
+};
+
+
+/* Wait a while until the busy flag clears. */
+static int w1_f19_i2c_busy_wait(struct w1_slave *sl, size_t count)
+{
+        const unsigned long timebases[3] = W1_F19_BUSY_TIMEBASES;
+        struct w1_f19_data *data = sl->family_data;
+        unsigned int checks;
+
+        /* Check the busy flag first in any case.*/
+        if (w1_touch_bit(sl->master, 1) == 0)
+                return 0;
+
+        /*
+         * Do a generously long sleep in the beginning,
+         * as we have to wait at least this time for all
+         * the I2C bytes at the given speed to be transferred.
+         */
+        usleep_range(timebases[data->speed] * (data->stretch) * count,
+                timebases[data->speed] * (data->stretch) * count
+                + W1_F19_BUSY_GRATUITY);
+
+        /* Now continusly check the busy flag sent by the DS28E17. */
+        checks = W1_F19_BUSY_CHECKS;
+        while ((checks--) > 0) {
+                /* Return success if the busy flag is cleared. */
+                if (w1_touch_bit(sl->master, 1) == 0)
+                        return 0;
+
+                /* Wait one non-streched byte timeslot. */
+                udelay(timebases[data->speed]);
+        }
+
+        /* Timeout. */
+        dev_warn(&sl->dev, "busy timeout\n");
+        return -ETIMEDOUT;
+}
+
+
+/* Utility function: result. */
+static size_t w1_f19_error(struct w1_slave *sl, u8 w1_buf[])
+{
+        /* Warnings. */
+        if (w1_buf[0] & W1_F19_STATUS_CRC)
+                dev_warn(&sl->dev, "crc16 mismatch\n");
+        if (w1_buf[0] & W1_F19_STATUS_ADDRESS)
+                dev_warn(&sl->dev, "i2c device not responding\n");
+        if ((w1_buf[0] & (W1_F19_STATUS_CRC | W1_F19_STATUS_ADDRESS)) == 0
+                        && w1_buf[1] != 0) {
+                dev_warn(&sl->dev, "i2c short write, %d bytes not acknowledged\n",
+                        w1_buf[1]);
+        }
+
+        /* Check error conditions. */
+        if (w1_buf[0] & W1_F19_STATUS_ADDRESS)
+                return -ENXIO;
+        if (w1_buf[0] & W1_F19_STATUS_START)
+                return -EAGAIN;
+        if (w1_buf[0] != 0 || w1_buf[1] != 0)
+                return -EIO;
+
+        /* All ok. */
+        return 0;
+}
+
+
+/* Utility function: write data to I2C slave, single chunk. */
+static int __w1_f19_i2c_write(struct w1_slave *sl,
+        const u8 *command, size_t command_count,
+        const u8 *buffer, size_t count)
+{
+        u16 crc;
+        int error;
+        u8 w1_buf[2];
+
+        /* Send command and I2C data to DS28E17. */
+        crc = crc16(CRC16_INIT, command, command_count);
+        w1_write_block(sl->master, command, command_count);
+
+        w1_buf[0] = count;
+        crc = crc16(crc, w1_buf, 1);
+        w1_write_8(sl->master, w1_buf[0]);
+
+        crc = crc16(crc, buffer, count);
+        w1_write_block(sl->master, buffer, count);
+
+        w1_buf[0] = ~(crc & 0xFF);
+        w1_buf[1] = ~((crc >> 8) & 0xFF);
+        w1_write_block(sl->master, w1_buf, 2);
+
+        /* Wait until busy flag clears (or timeout). */
+        if (w1_f19_i2c_busy_wait(sl, count + 1) < 0)
+                return -ETIMEDOUT;
+
+        /* Read status from DS28E17. */
+        w1_read_block(sl->master, w1_buf, 2);
+
+        /* Check error conditions. */
+        error = w1_f19_error(sl, w1_buf);
+        if (error < 0)
+                return error;
+
+        /* Return number of bytes written. */
+        return count;
+}
+
+
+/* Write data to I2C slave. */
+static int w1_f19_i2c_write(struct w1_slave *sl, u16 i2c_address,
+        const u8 *buffer, size_t count, bool stop)
+{
+        int result;
+        int remaining = count;
+        const u8 *p;
+        u8 command[2];
+
+        /* Check input. */
+        if (count == 0)
+                return -EOPNOTSUPP;
+
+        /* Check whether we need multiple commands. */
+        if (count <= W1_F19_WRITE_DATA_LIMIT) {
+                /*
+                 * Small data amount. Data can be sent with
+                 * a single onewire command.
+                 */
+
+                /* Send all data to DS28E17. */
+                command[0] = (stop ? W1_F19_WRITE_DATA_WITH_STOP
+                        : W1_F19_WRITE_DATA_NO_STOP);
+                command[1] = i2c_address << 1;
+                result = __w1_f19_i2c_write(sl, command, 2, buffer, count);
+        } else {
+                /* Large data amount. Data has to be sent in multiple chunks. */
+
+                /* Send first chunk to DS28E17. */
+                p = buffer;
+                command[0] = W1_F19_WRITE_DATA_NO_STOP;
+                command[1] = i2c_address << 1;
+                result = __w1_f19_i2c_write(sl, command, 2, p,
+                        W1_F19_WRITE_DATA_LIMIT);
+                if (result < 0)
+                        return result;
+
+                /* Resume to same DS28E17. */
+                if (w1_reset_resume_command(sl->master))
+                        return -EIO;
+
+                /* Next data chunk. */
+                p += W1_F19_WRITE_DATA_LIMIT;
+                remaining -= W1_F19_WRITE_DATA_LIMIT;
+
+                while (remaining > W1_F19_WRITE_DATA_LIMIT) {
+                        /* Send intermediate chunk to DS28E17. */
+                        command[0] = W1_F19_WRITE_DATA_ONLY;
+                        result = __w1_f19_i2c_write(sl, command, 1, p,
+                                        W1_F19_WRITE_DATA_LIMIT);
+                        if (result < 0)
+                                return result;
+
+                        /* Resume to same DS28E17. */
+                        if (w1_reset_resume_command(sl->master))
+                                return -EIO;
+
+                        /* Next data chunk. */
+                        p += W1_F19_WRITE_DATA_LIMIT;
+                        remaining -= W1_F19_WRITE_DATA_LIMIT;
+                }
+
+                /* Send final chunk to DS28E17. */
+                command[0] = (stop ? W1_F19_WRITE_DATA_ONLY_WITH_STOP
+                        : W1_F19_WRITE_DATA_ONLY);
+                result = __w1_f19_i2c_write(sl, command, 1, p, remaining);
+        }
+
+        return result;
+}
+
+
+/* Read data from I2C slave. */
+static int w1_f19_i2c_read(struct w1_slave *sl, u16 i2c_address,
+        u8 *buffer, size_t count)
+{
+        u16 crc;
+        int error;
+        u8 w1_buf[5];
+
+        /* Check input. */
+        if (count == 0)
+                return -EOPNOTSUPP;
+
+        /* Send command to DS28E17. */
+        w1_buf[0] = W1_F19_READ_DATA_WITH_STOP;
+        w1_buf[1] = i2c_address << 1 | 0x01;
+        w1_buf[2] = count;
+        crc = crc16(CRC16_INIT, w1_buf, 3);
+        w1_buf[3] = ~(crc & 0xFF);
+        w1_buf[4] = ~((crc >> 8) & 0xFF);
+        w1_write_block(sl->master, w1_buf, 5);
+
+        /* Wait until busy flag clears (or timeout). */
+        if (w1_f19_i2c_busy_wait(sl, count + 1) < 0)
+                return -ETIMEDOUT;
+
+        /* Read status from DS28E17. */
+        w1_buf[0] = w1_read_8(sl->master);
+        w1_buf[1] = 0;
+
+        /* Check error conditions. */
+        error = w1_f19_error(sl, w1_buf);
+        if (error < 0)
+                return error;
+
+        /* Read received I2C data from DS28E17. */
+        return w1_read_block(sl->master, buffer, count);
+}
+
+
+/* Write to, then read data from I2C slave. */
+static int w1_f19_i2c_write_read(struct w1_slave *sl, u16 i2c_address,
+        const u8 *wbuffer, size_t wcount, u8 *rbuffer, size_t rcount)
+{
+        u16 crc;
+        int error;
+        u8 w1_buf[3];
+
+        /* Check input. */
+        if (wcount == 0 || rcount == 0)
+                return -EOPNOTSUPP;
+
+        /* Send command and I2C data to DS28E17. */
+        w1_buf[0] = W1_F19_WRITE_READ_DATA_WITH_STOP;
+        w1_buf[1] = i2c_address << 1;
+        w1_buf[2] = wcount;
+        crc = crc16(CRC16_INIT, w1_buf, 3);
+        w1_write_block(sl->master, w1_buf, 3);
+
+        crc = crc16(crc, wbuffer, wcount);
+        w1_write_block(sl->master, wbuffer, wcount);
+
+        w1_buf[0] = rcount;
+        crc = crc16(crc, w1_buf, 1);
+        w1_buf[1] = ~(crc & 0xFF);
+        w1_buf[2] = ~((crc >> 8) & 0xFF);
+        w1_write_block(sl->master, w1_buf, 3);
+
+        /* Wait until busy flag clears (or timeout). */
+        if (w1_f19_i2c_busy_wait(sl, wcount + rcount + 2) < 0)
+                return -ETIMEDOUT;
+
+        /* Read status from DS28E17. */
+        w1_read_block(sl->master, w1_buf, 2);
+
+        /* Check error conditions. */
+        error = w1_f19_error(sl, w1_buf);
+        if (error < 0)
+                return error;
+
+        /* Read received I2C data from DS28E17. */
+        return w1_read_block(sl->master, rbuffer, rcount);
+}
+
+
+/* Do an I2C master transfer. */
+static int w1_f19_i2c_master_transfer(struct i2c_adapter *adapter,
+        struct i2c_msg *msgs, int num)
+{
+        struct w1_slave *sl = (struct w1_slave *) adapter->algo_data;
+        int i = 0;
+        int result = 0;
+
+        /* Start onewire transaction. */
+        mutex_lock(&sl->master->bus_mutex);
+
+        /* Select DS28E17. */
+        if (w1_reset_select_slave(sl)) {
+                i = -EIO;
+                goto error;
+        }
+
+        /* Loop while there are still messages to transfer. */
+        while (i < num) {
+                /*
+                 * Check for special case: Small write followed
+                 * by read to same I2C device.
+                 */
+                if (i < (num-1)
+                        && msgs[i].addr == msgs[i+1].addr
+                        && !(msgs[i].flags & I2C_M_RD)
+                        && (msgs[i+1].flags & I2C_M_RD)
+                        && (msgs[i].len <= W1_F19_WRITE_DATA_LIMIT)) {
+                        /*
+                         * The DS28E17 has a combined transfer
+                         * for small write+read.
+                         */
+                        result = w1_f19_i2c_write_read(sl, msgs[i].addr,
+                                msgs[i].buf, msgs[i].len,
+                                msgs[i+1].buf, msgs[i+1].len);
+                        if (result < 0) {
+                                i = result;
+                                goto error;
+                        }
+
+                        /*
+                         * Check if we should interpret the read data
+                         * as a length byte. The DS28E17 unfortunately
+                         * has no read without stop, so we can just do
+                         * another simple read in that case.
+                         */
+                        if (msgs[i+1].flags & I2C_M_RECV_LEN) {
+                                result = w1_f19_i2c_read(sl, msgs[i+1].addr,
+                                        &(msgs[i+1].buf[1]), msgs[i+1].buf[0]);
+                                if (result < 0) {
+                                        i = result;
+                                        goto error;
+                                }
+                        }
+
+                        /* Eat up read message, too. */
+                        i++;
+                } else if (msgs[i].flags & I2C_M_RD) {
+                        /* Read transfer. */
+                        result = w1_f19_i2c_read(sl, msgs[i].addr,
+                                msgs[i].buf, msgs[i].len);
+                        if (result < 0) {
+                                i = result;
+                                goto error;
+                        }
+
+                        /*
+                         * Check if we should interpret the read data
+                         * as a length byte. The DS28E17 unfortunately
+                         * has no read without stop, so we can just do
+                         * another simple read in that case.
+                         */
+                        if (msgs[i].flags & I2C_M_RECV_LEN) {
+                                result = w1_f19_i2c_read(sl,
+                                        msgs[i].addr,
+                                        &(msgs[i].buf[1]),
+                                        msgs[i].buf[0]);
+                                if (result < 0) {
+                                        i = result;
+                                        goto error;
+                                }
+                        }
+                } else {
+                        /*
+                         * Write transfer.
+                         * Stop condition only for last
+                         * transfer.
+                         */
+                        result = w1_f19_i2c_write(sl,
+                                msgs[i].addr,
+                                msgs[i].buf,
+                                msgs[i].len,
+                                i == (num-1));
+                        if (result < 0) {
+                                i = result;
+                                goto error;
+                        }
+                }
+
+                /* Next message. */
+                i++;
+
+                /* Are there still messages to send/receive? */
+                if (i < num) {
+                        /* Yes. Resume to same DS28E17. */
+                        if (w1_reset_resume_command(sl->master)) {
+                                i = -EIO;
+                                goto error;
+                        }
+                }
+        }
+
+error:
+        /* End onewire transaction. */
+        mutex_unlock(&sl->master->bus_mutex);
+
+        /* Return number of messages processed or error. */
+        return i;
+}
+
+
+/* Get I2C adapter functionality. */
+static u32 w1_f19_i2c_functionality(struct i2c_adapter *adapter)
+{
+        /*
+         * Plain I2C functions only.
+         * SMBus is emulated by the kernel's I2C layer.
+         * No "I2C_FUNC_SMBUS_QUICK"
+         * No "I2C_FUNC_SMBUS_READ_BLOCK_DATA"
+         * No "I2C_FUNC_SMBUS_BLOCK_PROC_CALL"
+         */
+        return I2C_FUNC_I2C |
+                I2C_FUNC_SMBUS_BYTE |
+                I2C_FUNC_SMBUS_BYTE_DATA |
+                I2C_FUNC_SMBUS_WORD_DATA |
+                I2C_FUNC_SMBUS_PROC_CALL |
+                I2C_FUNC_SMBUS_WRITE_BLOCK_DATA |
+                I2C_FUNC_SMBUS_I2C_BLOCK |
+                I2C_FUNC_SMBUS_PEC;
+}
+
+
+/* I2C adapter quirks. */
+static const struct i2c_adapter_quirks w1_f19_i2c_adapter_quirks = {
+        .max_read_len = W1_F19_READ_DATA_LIMIT,
+};
+
+/* I2C algorithm. */
+static const struct i2c_algorithm w1_f19_i2c_algorithm = {
+        .master_xfer    = w1_f19_i2c_master_transfer,
+        .functionality  = w1_f19_i2c_functionality,
+};
+
+
+/* Read I2C speed from DS28E17. */
+static int w1_f19_get_i2c_speed(struct w1_slave *sl)
+{
+        struct w1_f19_data *data = sl->family_data;
+        int result = -EIO;
+
+        /* Start onewire transaction. */
+        mutex_lock(&sl->master->bus_mutex);
+
+        /* Select slave. */
+        if (w1_reset_select_slave(sl))
+                goto error;
+
+        /* Read slave configuration byte. */
+        w1_write_8(sl->master, W1_F19_READ_CONFIGURATION);
+        result = w1_read_8(sl->master);
+        if (result < 0 || result > 2) {
+                result = -EIO;
+                goto error;
+        }
+
+        /* Update speed in slave specific data. */
+        data->speed = result;
+
+error:
+        /* End onewire transaction. */
+        mutex_unlock(&sl->master->bus_mutex);
+
+        return result;
+}
+
+
+/* Set I2C speed on DS28E17. */
+static int __w1_f19_set_i2c_speed(struct w1_slave *sl, u8 speed)
+{
+        struct w1_f19_data *data = sl->family_data;
+        const int i2c_speeds[3] = { 100, 400, 900 };
+        u8 w1_buf[2];
+
+        /* Select slave. */
+        if (w1_reset_select_slave(sl))
+                return -EIO;
+
+        w1_buf[0] = W1_F19_WRITE_CONFIGURATION;
+        w1_buf[1] = speed;
+        w1_write_block(sl->master, w1_buf, 2);
+
+        /* Update speed in slave specific data. */
+        data->speed = speed;
+
+        dev_info(&sl->dev, "i2c speed set to %d kBaud\n", i2c_speeds[speed]);
+
+        return 0;
+}
+
+static int w1_f19_set_i2c_speed(struct w1_slave *sl, u8 speed)
+{
+        int result;
+
+        /* Start onewire transaction. */
+        mutex_lock(&sl->master->bus_mutex);
+
+        /* Set I2C speed on DS28E17. */
+        result = __w1_f19_set_i2c_speed(sl, speed);
+
+        /* End onewire transaction. */
+        mutex_unlock(&sl->master->bus_mutex);
+
+        return result;
+}
+
+
+/* Sysfs attributes. */
+
+/* I2C speed attribute for a single chip. */
+static ssize_t speed_show(struct device *dev, struct device_attribute *attr,
+                             char *buf)
+{
+        struct w1_slave *sl = dev_to_w1_slave(dev);
+        int result;
+
+        /* Read current speed from slave. Updates data->speed. */
+        result = w1_f19_get_i2c_speed(sl);
+        if (result < 0)
+                return result;
+
+        /* Return current speed value. */
+        return sprintf(buf, "%d\n", result);
+}
+
+static ssize_t speed_store(struct device *dev, struct device_attribute *attr,
+                              const char *buf, size_t count)
+{
+        struct w1_slave *sl = dev_to_w1_slave(dev);
+        int error;
+
+        /* Valid values are: "100", "400", "900" */
+        if (count < 3 || count > 4 || !buf)
+                return -EINVAL;
+        if (count == 4 && buf[3] != '\n')
+                return -EINVAL;
+        if (buf[1] != '0' || buf[2] != '0')
+                return -EINVAL;
+
+        /* Set speed on slave. */
+        switch (buf[0]) {
+        case '1':
+                error = w1_f19_set_i2c_speed(sl, 0);
+                break;
+        case '4':
+                error = w1_f19_set_i2c_speed(sl, 1);
+                break;
+        case '9':
+                error = w1_f19_set_i2c_speed(sl, 2);
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        if (error < 0)
+                return error;
+
+        /* Return bytes written. */
+        return count;
+}
+
+static DEVICE_ATTR_RW(speed);
+
+
+/* Busy stretch attribute for a single chip. */
+static ssize_t stretch_show(struct device *dev, struct device_attribute *attr,
+                             char *buf)
+{
+        struct w1_slave *sl = dev_to_w1_slave(dev);
+        struct w1_f19_data *data = sl->family_data;
+
+        /* Return current stretch value. */
+        return sprintf(buf, "%d\n", data->stretch);
+}
+
+static ssize_t stretch_store(struct device *dev, struct device_attribute *attr,
+                              const char *buf, size_t count)
+{
+        struct w1_slave *sl = dev_to_w1_slave(dev);
+        struct w1_f19_data *data = sl->family_data;
+
+        /* Valid values are '1' to '9' */
+        if (count < 1 || count > 2 || !buf)
+                return -EINVAL;
+        if (count == 2 && buf[1] != '\n')
+                return -EINVAL;
+        if (buf[0] < '1' || buf[0] > '9')
+                return -EINVAL;
+
+        /* Set busy stretch value. */
+        data->stretch = buf[0] & 0x0F;
+
+        /* Return bytes written. */
+        return count;
+}
+
+static DEVICE_ATTR_RW(stretch);
+
+
+/* All attributes. */
+static struct attribute *w1_f19_attrs[] = {
+        &dev_attr_speed.attr,
+        &dev_attr_stretch.attr,
+        NULL,
+};
+
+static const struct attribute_group w1_f19_group = {
+        .attrs          = w1_f19_attrs,
+};
+
+static const struct attribute_group *w1_f19_groups[] = {
+        &w1_f19_group,
+        NULL,
+};
+
+
+/* Slave add and remove functions. */
+static int w1_f19_add_slave(struct w1_slave *sl)
+{
+        struct w1_f19_data *data = NULL;
+
+        /* Allocate memory for slave specific data. */
+        data = devm_kzalloc(&sl->dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+        sl->family_data = data;
+
+        /* Setup default I2C speed on slave. */
+        switch (i2c_speed) {
+        case 100:
+                __w1_f19_set_i2c_speed(sl, 0);
+                break;
+        case 400:
+                __w1_f19_set_i2c_speed(sl, 1);
+                break;
+        case 900:
+                __w1_f19_set_i2c_speed(sl, 2);
+                break;
+        default:
+                /*
+                 * A i2c_speed module parameter of anything else
+                 * than 100, 400, 900 means not to touch the
+                 * speed of the DS28E17.
+                 * We assume 400kBaud, the power-on value.
+                 */
+                data->speed = 1;
+        }
+
+        /*
+         * Setup default busy stretch
+         * configuration for the DS28E17.
+         */
+        data->stretch = i2c_stretch;
+
+        /* Setup I2C adapter. */
+        data->adapter.owner      = THIS_MODULE;
+        data->adapter.algo       = &w1_f19_i2c_algorithm;
+        data->adapter.algo_data  = sl;
+        strcpy(data->adapter.name, "w1-");
+        strcat(data->adapter.name, sl->name);
+        data->adapter.dev.parent = &sl->dev;
+        data->adapter.quirks     = &w1_f19_i2c_adapter_quirks;
+
+        return i2c_add_adapter(&data->adapter);
+}
+
+static void w1_f19_remove_slave(struct w1_slave *sl)
+{
+        struct w1_f19_data *family_data = sl->family_data;
+
+        /* Delete I2C adapter. */
+        i2c_del_adapter(&family_data->adapter);
+
+        /* Free slave specific data. */
+        devm_kfree(&sl->dev, family_data);
+        sl->family_data = NULL;
+}
+
+
+/* Declarations within the w1 subsystem. */
+static struct w1_family_ops w1_f19_fops = {
+        .add_slave = w1_f19_add_slave,
+        .remove_slave = w1_f19_remove_slave,
+        .groups = w1_f19_groups,
+};
+
+static struct w1_family w1_family_19 = {
+        .fid = W1_FAMILY_DS28E17,
+        .fops = &w1_f19_fops,
+};
+
+
+/* Module init and remove functions. */
+static int __init w1_f19_init(void)
+{
+        return w1_register_family(&w1_family_19);
+}
+
+static void __exit w1_f19_fini(void)
+{
+        w1_unregister_family(&w1_family_19);
+}
+
+module_init(w1_f19_init);
+module_exit(w1_f19_fini);
+