Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 619 insertions, 0 deletions

diff --git a/drivers/hwmon/drivetemp.c b/drivers/hwmon/drivetemp.c
new file mode 100644
index 000000000..efe8b229b
--- /dev/null
+++ b/drivers/hwmon/drivetemp.c
@@ -0,0 +1,619 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hwmon client for disk and solid state drives with temperature sensors
+ * Copyright (C) 2019 Zodiac Inflight Innovations
+ *
+ * With input from:
+ *    Hwmon client for S.M.A.R.T. hard disk drives with temperature sensors.
+ *    (C) 2018 Linus Walleij
+ *
+ *    hwmon: Driver for SCSI/ATA temperature sensors
+ *    by Constantin Baranov <const@mimas.ru>, submitted September 2009
+ *
+ * This drive supports reporting the temperature of SATA drives. It can be
+ * easily extended to report the temperature of SCSI drives.
+ *
+ * The primary means to read drive temperatures and temperature limits
+ * for ATA drives is the SCT Command Transport feature set as specified in
+ * ATA8-ACS.
+ * It can be used to read the current drive temperature, temperature limits,
+ * and historic minimum and maximum temperatures. The SCT Command Transport
+ * feature set is documented in "AT Attachment 8 - ATA/ATAPI Command Set
+ * (ATA8-ACS)".
+ *
+ * If the SCT Command Transport feature set is not available, drive temperatures
+ * may be readable through SMART attributes. Since SMART attributes are not well
+ * defined, this method is only used as fallback mechanism.
+ *
+ * There are three SMART attributes which may report drive temperatures.
+ * Those are defined as follows (from
+ * http://www.cropel.com/library/smart-attribute-list.aspx).
+ *
+ * 190	Temperature	Temperature, monitored by a sensor somewhere inside
+ *			the drive. Raw value typicaly holds the actual
+ *			temperature (hexadecimal) in its rightmost two digits.
+ *
+ * 194	Temperature	Temperature, monitored by a sensor somewhere inside
+ *			the drive. Raw value typicaly holds the actual
+ *			temperature (hexadecimal) in its rightmost two digits.
+ *
+ * 231	Temperature	Temperature, monitored by a sensor somewhere inside
+ *			the drive. Raw value typicaly holds the actual
+ *			temperature (hexadecimal) in its rightmost two digits.
+ *
+ * Wikipedia defines attributes a bit differently.
+ *
+ * 190	Temperature	Value is equal to (100-temp. °C), allowing manufacturer
+ *	Difference or	to set a minimum threshold which corresponds to a
+ *	Airflow		maximum temperature. This also follows the convention of
+ *	Temperature	100 being a best-case value and lower values being
+ *			undesirable. However, some older drives may instead
+ *			report raw Temperature (identical to 0xC2) or
+ *			Temperature minus 50 here.
+ * 194	Temperature or	Indicates the device temperature, if the appropriate
+ *	Temperature	sensor is fitted. Lowest byte of the raw value contains
+ *	Celsius		the exact temperature value (Celsius degrees).
+ * 231	Life Left	Indicates the approximate SSD life left, in terms of
+ *	(SSDs) or	program/erase cycles or available reserved blocks.
+ *	Temperature	A normalized value of 100 represents a new drive, with
+ *			a threshold value at 10 indicating a need for
+ *			replacement. A value of 0 may mean that the drive is
+ *			operating in read-only mode to allow data recovery.
+ *			Previously (pre-2010) occasionally used for Drive
+ *			Temperature (more typically reported at 0xC2).
+ *
+ * Common denominator is that the first raw byte reports the temperature
+ * in degrees C on almost all drives. Some drives may report a fractional
+ * temperature in the second raw byte.
+ *
+ * Known exceptions (from libatasmart):
+ * - SAMSUNG SV0412H and SAMSUNG SV1204H) report the temperature in 10th
+ *   degrees C in the first two raw bytes.
+ * - A few Maxtor drives report an unknown or bad value in attribute 194.
+ * - Certain Apple SSD drives report an unknown value in attribute 190.
+ *   Only certain firmware versions are affected.
+ *
+ * Those exceptions affect older ATA drives and are currently ignored.
+ * Also, the second raw byte (possibly reporting the fractional temperature)
+ * is currently ignored.
+ *
+ * Many drives also report temperature limits in additional SMART data raw
+ * bytes. The format of those is not well defined and varies widely.
+ * The driver does not currently attempt to report those limits.
+ *
+ * According to data in smartmontools, attribute 231 is rarely used to report
+ * drive temperatures. At the same time, several drives report SSD life left
+ * in attribute 231, but do not support temperature sensors. For this reason,
+ * attribute 231 is currently ignored.
+ *
+ * Following above definitions, temperatures are reported as follows.
+ *   If SCT Command Transport is supported, it is used to read the
+ *   temperature and, if available, temperature limits.
+ * - Otherwise, if SMART attribute 194 is supported, it is used to read
+ *   the temperature.
+ * - Otherwise, if SMART attribute 190 is supported, it is used to read
+ *   the temperature.
+ */
+
+#include <linux/ata.h>
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_driver.h>
+#include <scsi/scsi_proto.h>
+
+struct drivetemp_data {
+	struct list_head list;		/* list of instantiated devices */
+	struct scsi_device *sdev;	/* SCSI device */
+	struct device *dev;		/* instantiating device */
+	struct device *hwdev;		/* hardware monitoring device */
+	u8 smartdata[ATA_SECT_SIZE];	/* local buffer */
+	int (*get_temp)(struct drivetemp_data *st, u32 attr, long *val);
+	bool have_temp_lowest;		/* lowest temp in SCT status */
+	bool have_temp_highest;		/* highest temp in SCT status */
+	bool have_temp_min;		/* have min temp */
+	bool have_temp_max;		/* have max temp */
+	bool have_temp_lcrit;		/* have lower critical limit */
+	bool have_temp_crit;		/* have critical limit */
+	int temp_min;			/* min temp */
+	int temp_max;			/* max temp */
+	int temp_lcrit;			/* lower critical limit */
+	int temp_crit;			/* critical limit */
+};
+
+static LIST_HEAD(drivetemp_devlist);
+
+#define ATA_MAX_SMART_ATTRS	30
+#define SMART_TEMP_PROP_190	190
+#define SMART_TEMP_PROP_194	194
+
+#define SCT_STATUS_REQ_ADDR	0xe0
+#define  SCT_STATUS_VERSION_LOW		0	/* log byte offsets */
+#define  SCT_STATUS_VERSION_HIGH	1
+#define  SCT_STATUS_TEMP		200
+#define  SCT_STATUS_TEMP_LOWEST		201
+#define  SCT_STATUS_TEMP_HIGHEST	202
+#define SCT_READ_LOG_ADDR	0xe1
+#define  SMART_READ_LOG			0xd5
+#define  SMART_WRITE_LOG		0xd6
+
+#define INVALID_TEMP		0x80
+
+#define temp_is_valid(temp)	((temp) != INVALID_TEMP)
+#define temp_from_sct(temp)	(((s8)(temp)) * 1000)
+
+static inline bool ata_id_smart_supported(u16 *id)
+{
+	return id[ATA_ID_COMMAND_SET_1] & BIT(0);
+}
+
+static inline bool ata_id_smart_enabled(u16 *id)
+{
+	return id[ATA_ID_CFS_ENABLE_1] & BIT(0);
+}
+
+static int drivetemp_scsi_command(struct drivetemp_data *st,
+				 u8 ata_command, u8 feature,
+				 u8 lba_low, u8 lba_mid, u8 lba_high)
+{
+	u8 scsi_cmd[MAX_COMMAND_SIZE];
+	enum req_op op;
+	int err;
+
+	memset(scsi_cmd, 0, sizeof(scsi_cmd));
+	scsi_cmd[0] = ATA_16;
+	if (ata_command == ATA_CMD_SMART && feature == SMART_WRITE_LOG) {
+		scsi_cmd[1] = (5 << 1);	/* PIO Data-out */
+		/*
+		 * No off.line or cc, write to dev, block count in sector count
+		 * field.
+		 */
+		scsi_cmd[2] = 0x06;
+		op = REQ_OP_DRV_OUT;
+	} else {
+		scsi_cmd[1] = (4 << 1);	/* PIO Data-in */
+		/*
+		 * No off.line or cc, read from dev, block count in sector count
+		 * field.
+		 */
+		scsi_cmd[2] = 0x0e;
+		op = REQ_OP_DRV_IN;
+	}
+	scsi_cmd[4] = feature;
+	scsi_cmd[6] = 1;	/* 1 sector */
+	scsi_cmd[8] = lba_low;
+	scsi_cmd[10] = lba_mid;
+	scsi_cmd[12] = lba_high;
+	scsi_cmd[14] = ata_command;
+
+	err = scsi_execute_cmd(st->sdev, scsi_cmd, op, st->smartdata,
+			       ATA_SECT_SIZE, 10 * HZ, 5, NULL);
+	if (err > 0)
+		err = -EIO;
+	return err;
+}
+
+static int drivetemp_ata_command(struct drivetemp_data *st, u8 feature,
+				 u8 select)
+{
+	return drivetemp_scsi_command(st, ATA_CMD_SMART, feature, select,
+				     ATA_SMART_LBAM_PASS, ATA_SMART_LBAH_PASS);
+}
+
+static int drivetemp_get_smarttemp(struct drivetemp_data *st, u32 attr,
+				  long *temp)
+{
+	u8 *buf = st->smartdata;
+	bool have_temp = false;
+	u8 temp_raw;
+	u8 csum;
+	int err;
+	int i;
+
+	err = drivetemp_ata_command(st, ATA_SMART_READ_VALUES, 0);
+	if (err)
+		return err;
+
+	/* Checksum the read value table */
+	csum = 0;
+	for (i = 0; i < ATA_SECT_SIZE; i++)
+		csum += buf[i];
+	if (csum) {
+		dev_dbg(&st->sdev->sdev_gendev,
+			"checksum error reading SMART values\n");
+		return -EIO;
+	}
+
+	for (i = 0; i < ATA_MAX_SMART_ATTRS; i++) {
+		u8 *attr = buf + i * 12;
+		int id = attr[2];
+
+		if (!id)
+			continue;
+
+		if (id == SMART_TEMP_PROP_190) {
+			temp_raw = attr[7];
+			have_temp = true;
+		}
+		if (id == SMART_TEMP_PROP_194) {
+			temp_raw = attr[7];
+			have_temp = true;
+			break;
+		}
+	}
+
+	if (have_temp) {
+		*temp = temp_raw * 1000;
+		return 0;
+	}
+
+	return -ENXIO;
+}
+
+static int drivetemp_get_scttemp(struct drivetemp_data *st, u32 attr, long *val)
+{
+	u8 *buf = st->smartdata;
+	int err;
+
+	err = drivetemp_ata_command(st, SMART_READ_LOG, SCT_STATUS_REQ_ADDR);
+	if (err)
+		return err;
+	switch (attr) {
+	case hwmon_temp_input:
+		if (!temp_is_valid(buf[SCT_STATUS_TEMP]))
+			return -ENODATA;
+		*val = temp_from_sct(buf[SCT_STATUS_TEMP]);
+		break;
+	case hwmon_temp_lowest:
+		if (!temp_is_valid(buf[SCT_STATUS_TEMP_LOWEST]))
+			return -ENODATA;
+		*val = temp_from_sct(buf[SCT_STATUS_TEMP_LOWEST]);
+		break;
+	case hwmon_temp_highest:
+		if (!temp_is_valid(buf[SCT_STATUS_TEMP_HIGHEST]))
+			return -ENODATA;
+		*val = temp_from_sct(buf[SCT_STATUS_TEMP_HIGHEST]);
+		break;
+	default:
+		err = -EINVAL;
+		break;
+	}
+	return err;
+}
+
+static const char * const sct_avoid_models[] = {
+/*
+ * These drives will have WRITE FPDMA QUEUED command timeouts and sometimes just
+ * freeze until power-cycled under heavy write loads when their temperature is
+ * getting polled in SCT mode. The SMART mode seems to be fine, though.
+ *
+ * While only the 3 TB model (DT01ACA3) was actually caught exhibiting the
+ * problem let's play safe here to avoid data corruption and ban the whole
+ * DT01ACAx family.
+
+ * The models from this array are prefix-matched.
+ */
+	"TOSHIBA DT01ACA",
+};
+
+static bool drivetemp_sct_avoid(struct drivetemp_data *st)
+{
+	struct scsi_device *sdev = st->sdev;
+	unsigned int ctr;
+
+	/*
+	 * The "model" field contains just the raw SCSI INQUIRY response
+	 * "product identification" field, which has a width of 16 bytes.
+	 * This field is space-filled and NUL-terminated.
+	 */
+	for (ctr = 0; ctr < ARRAY_SIZE(sct_avoid_models); ctr++)
+		if (!strncmp(sdev->model, sct_avoid_models[ctr],
+			     strlen(sct_avoid_models[ctr])))
+			return true;
+
+	return false;
+}
+
+static int drivetemp_identify_sata(struct drivetemp_data *st)
+{
+	struct scsi_device *sdev = st->sdev;
+	u8 *buf = st->smartdata;
+	struct scsi_vpd *vpd;
+	bool is_ata, is_sata;
+	bool have_sct_data_table;
+	bool have_sct_temp;
+	bool have_smart;
+	bool have_sct;
+	u16 *ata_id;
+	u16 version;
+	long temp;
+	int err;
+
+	/* SCSI-ATA Translation present? */
+	rcu_read_lock();
+	vpd = rcu_dereference(sdev->vpd_pg89);
+
+	/*
+	 * Verify that ATA IDENTIFY DEVICE data is included in ATA Information
+	 * VPD and that the drive implements the SATA protocol.
+	 */
+	if (!vpd || vpd->len < 572 || vpd->data[56] != ATA_CMD_ID_ATA ||
+	    vpd->data[36] != 0x34) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+	ata_id = (u16 *)&vpd->data[60];
+	is_ata = ata_id_is_ata(ata_id);
+	is_sata = ata_id_is_sata(ata_id);
+	have_sct = ata_id_sct_supported(ata_id);
+	have_sct_data_table = ata_id_sct_data_tables(ata_id);
+	have_smart = ata_id_smart_supported(ata_id) &&
+				ata_id_smart_enabled(ata_id);
+
+	rcu_read_unlock();
+
+	/* bail out if this is not a SATA device */
+	if (!is_ata || !is_sata)
+		return -ENODEV;
+
+	if (have_sct && drivetemp_sct_avoid(st)) {
+		dev_notice(&sdev->sdev_gendev,
+			   "will avoid using SCT for temperature monitoring\n");
+		have_sct = false;
+	}
+
+	if (!have_sct)
+		goto skip_sct;
+
+	err = drivetemp_ata_command(st, SMART_READ_LOG, SCT_STATUS_REQ_ADDR);
+	if (err)
+		goto skip_sct;
+
+	version = (buf[SCT_STATUS_VERSION_HIGH] << 8) |
+		  buf[SCT_STATUS_VERSION_LOW];
+	if (version != 2 && version != 3)
+		goto skip_sct;
+
+	have_sct_temp = temp_is_valid(buf[SCT_STATUS_TEMP]);
+	if (!have_sct_temp)
+		goto skip_sct;
+
+	st->have_temp_lowest = temp_is_valid(buf[SCT_STATUS_TEMP_LOWEST]);
+	st->have_temp_highest = temp_is_valid(buf[SCT_STATUS_TEMP_HIGHEST]);
+
+	if (!have_sct_data_table)
+		goto skip_sct_data;
+
+	/* Request and read temperature history table */
+	memset(buf, '\0', sizeof(st->smartdata));
+	buf[0] = 5;	/* data table command */
+	buf[2] = 1;	/* read table */
+	buf[4] = 2;	/* temperature history table */
+
+	err = drivetemp_ata_command(st, SMART_WRITE_LOG, SCT_STATUS_REQ_ADDR);
+	if (err)
+		goto skip_sct_data;
+
+	err = drivetemp_ata_command(st, SMART_READ_LOG, SCT_READ_LOG_ADDR);
+	if (err)
+		goto skip_sct_data;
+
+	/*
+	 * Temperature limits per AT Attachment 8 -
+	 * ATA/ATAPI Command Set (ATA8-ACS)
+	 */
+	st->have_temp_max = temp_is_valid(buf[6]);
+	st->have_temp_crit = temp_is_valid(buf[7]);
+	st->have_temp_min = temp_is_valid(buf[8]);
+	st->have_temp_lcrit = temp_is_valid(buf[9]);
+
+	st->temp_max = temp_from_sct(buf[6]);
+	st->temp_crit = temp_from_sct(buf[7]);
+	st->temp_min = temp_from_sct(buf[8]);
+	st->temp_lcrit = temp_from_sct(buf[9]);
+
+skip_sct_data:
+	if (have_sct_temp) {
+		st->get_temp = drivetemp_get_scttemp;
+		return 0;
+	}
+skip_sct:
+	if (!have_smart)
+		return -ENODEV;
+	st->get_temp = drivetemp_get_smarttemp;
+	return drivetemp_get_smarttemp(st, hwmon_temp_input, &temp);
+}
+
+static int drivetemp_identify(struct drivetemp_data *st)
+{
+	struct scsi_device *sdev = st->sdev;
+
+	/* Bail out immediately if there is no inquiry data */
+	if (!sdev->inquiry || sdev->inquiry_len < 16)
+		return -ENODEV;
+
+	/* Disk device? */
+	if (sdev->type != TYPE_DISK && sdev->type != TYPE_ZBC)
+		return -ENODEV;
+
+	return drivetemp_identify_sata(st);
+}
+
+static int drivetemp_read(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long *val)
+{
+	struct drivetemp_data *st = dev_get_drvdata(dev);
+	int err = 0;
+
+	if (type != hwmon_temp)
+		return -EINVAL;
+
+	switch (attr) {
+	case hwmon_temp_input:
+	case hwmon_temp_lowest:
+	case hwmon_temp_highest:
+		err = st->get_temp(st, attr, val);
+		break;
+	case hwmon_temp_lcrit:
+		*val = st->temp_lcrit;
+		break;
+	case hwmon_temp_min:
+		*val = st->temp_min;
+		break;
+	case hwmon_temp_max:
+		*val = st->temp_max;
+		break;
+	case hwmon_temp_crit:
+		*val = st->temp_crit;
+		break;
+	default:
+		err = -EINVAL;
+		break;
+	}
+	return err;
+}
+
+static umode_t drivetemp_is_visible(const void *data,
+				   enum hwmon_sensor_types type,
+				   u32 attr, int channel)
+{
+	const struct drivetemp_data *st = data;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return 0444;
+		case hwmon_temp_lowest:
+			if (st->have_temp_lowest)
+				return 0444;
+			break;
+		case hwmon_temp_highest:
+			if (st->have_temp_highest)
+				return 0444;
+			break;
+		case hwmon_temp_min:
+			if (st->have_temp_min)
+				return 0444;
+			break;
+		case hwmon_temp_max:
+			if (st->have_temp_max)
+				return 0444;
+			break;
+		case hwmon_temp_lcrit:
+			if (st->have_temp_lcrit)
+				return 0444;
+			break;
+		case hwmon_temp_crit:
+			if (st->have_temp_crit)
+				return 0444;
+			break;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+static const struct hwmon_channel_info * const drivetemp_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ),
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT |
+			   HWMON_T_LOWEST | HWMON_T_HIGHEST |
+			   HWMON_T_MIN | HWMON_T_MAX |
+			   HWMON_T_LCRIT | HWMON_T_CRIT),
+	NULL
+};
+
+static const struct hwmon_ops drivetemp_ops = {
+	.is_visible = drivetemp_is_visible,
+	.read = drivetemp_read,
+};
+
+static const struct hwmon_chip_info drivetemp_chip_info = {
+	.ops = &drivetemp_ops,
+	.info = drivetemp_info,
+};
+
+/*
+ * The device argument points to sdev->sdev_dev. Its parent is
+ * sdev->sdev_gendev, which we can use to get the scsi_device pointer.
+ */
+static int drivetemp_add(struct device *dev)
+{
+	struct scsi_device *sdev = to_scsi_device(dev->parent);
+	struct drivetemp_data *st;
+	int err;
+
+	st = kzalloc_obj(*st);
+	if (!st)
+		return -ENOMEM;
+
+	st->sdev = sdev;
+	st->dev = dev;
+
+	if (drivetemp_identify(st)) {
+		err = -ENODEV;
+		goto abort;
+	}
+
+	st->hwdev = hwmon_device_register_with_info(dev->parent, "drivetemp",
+						    st, &drivetemp_chip_info,
+						    NULL);
+	if (IS_ERR(st->hwdev)) {
+		err = PTR_ERR(st->hwdev);
+		goto abort;
+	}
+
+	list_add(&st->list, &drivetemp_devlist);
+	return 0;
+
+abort:
+	kfree(st);
+	return err;
+}
+
+static void drivetemp_remove(struct device *dev)
+{
+	struct drivetemp_data *st, *tmp;
+
+	list_for_each_entry_safe(st, tmp, &drivetemp_devlist, list) {
+		if (st->dev == dev) {
+			list_del(&st->list);
+			hwmon_device_unregister(st->hwdev);
+			kfree(st);
+			break;
+		}
+	}
+}
+
+static struct class_interface drivetemp_interface = {
+	.add_dev = drivetemp_add,
+	.remove_dev = drivetemp_remove,
+};
+
+static int __init drivetemp_init(void)
+{
+	return scsi_register_interface(&drivetemp_interface);
+}
+
+static void __exit drivetemp_exit(void)
+{
+	scsi_unregister_interface(&drivetemp_interface);
+}
+
+module_init(drivetemp_init);
+module_exit(drivetemp_exit);
+
+MODULE_AUTHOR("Guenter Roeck <linus@roeck-us.net>");
+MODULE_DESCRIPTION("Hard drive temperature monitor");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:drivetemp");