[v6,3/3] hwmon: (nct6775) Support access via Asus WMI.

Commit Message

Denis Pauk Sept. 15, 2021, 8:42 p.m. UTC

Support accessing the NCT677x via Asus WMI functions.

On mainboards that support this way of accessing the chip, the driver will
usually not work without this option since in these mainboards, ACPI will
mark the I/O port as used.

Code uses ACPI firmware interface to commucate with sensors with ASUS
motherboards:
* PRIME B460-PLUS,
* ROG CROSSHAIR VIII IMPACT,
* ROG STRIX B550-E GAMING,
* ROG STRIX B550-F GAMING,
* ROG STRIX B550-F GAMING (WI-FI),
* ROG STRIX Z490-I GAMING,
* TUF GAMING B550M-PLUS,
* TUF GAMING B550M-PLUS (WI-FI),
* TUF GAMING B550-PLUS,
* TUF GAMING X570-PLUS,
* TUF GAMING X570-PRO (WI-FI).

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204807
Signed-off-by: Denis Pauk <[e-mail]>
Co-developed-by: Bernhard Seibold <[e-mail]>
Signed-off-by: Bernhard Seibold <[e-mail]>
Tested-by: Pär Ekholm <[e-mail]>
Tested-by: <[e-mail]>
Tested-by: Artem S. Tashkinov <[e-mail]>
Tested-by: Vittorio Roberto Alfieri <[e-mail]>
Tested-by: Sahan Fernando <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: Guenter Roeck <[e-mail]>

---
Changes in v6:
  - Minimaze codes inside code inside defined(CONFIG_ACPI_WMI).

Changes in v5:
  - Use IS_ENABLED(CONFIG_ACPI_WMI) instead defined(CONFIG_ACPI_WMI)

Changes in v4:
  - Fix build without ACPI WMI.

Changes in v3:
  - Remove unrequired type conversions.
  - Save result of match_string before check.

Changes in v2:
  - Split changes to separate patches.
  - Limit WMI usage by DMI_BOARD_NAME in checked ASUS motherboards.
---
 drivers/hwmon/Kconfig   |   1 +
 drivers/hwmon/nct6775.c | 232 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 212 insertions(+), 21 deletions(-)

Comments

Andy Shevchenko Sept. 16, 2021, 8:34 a.m. UTC | #1

On Wed, Sep 15, 2021 at 11:45 PM Denis Pauk <[e-mail]> wrote:
>
> Support accessing the NCT677x via Asus WMI functions.
>
> On mainboards that support this way of accessing the chip, the driver will
> usually not work without this option since in these mainboards, ACPI will
> mark the I/O port as used.
>
> Code uses ACPI firmware interface to commucate with sensors with ASUS

communicate

> motherboards:
> * PRIME B460-PLUS,
> * ROG CROSSHAIR VIII IMPACT,
> * ROG STRIX B550-E GAMING,
> * ROG STRIX B550-F GAMING,
> * ROG STRIX B550-F GAMING (WI-FI),
> * ROG STRIX Z490-I GAMING,
> * TUF GAMING B550M-PLUS,
> * TUF GAMING B550M-PLUS (WI-FI),
> * TUF GAMING B550-PLUS,
> * TUF GAMING X570-PLUS,
> * TUF GAMING X570-PRO (WI-FI).

...

> +static int asuswmi_evaluate_method(u32 method_id, u8 bank, u8 reg, u8 val, u32 *retval)
> +{

> +#if IS_ENABLED(CONFIG_ACPI_WMI)

The idea behind IS_ENABLED() macro is that it may be used in C
conditionals, like

if (IS_ENABLED(...))

> +       u32 args = bank | (reg << 8) | (val << 16);
> +       struct acpi_buffer input = { (acpi_size) sizeof(args), &args };
> +       struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
> +       acpi_status status;
> +       union acpi_object *obj;
> +       u32 tmp = 0;

> +       obj = output.pointer;
> +       if (obj && obj->type == ACPI_TYPE_INTEGER)
> +               tmp = obj->integer.value;
> +
> +       if (retval)
> +               *retval = tmp;
> +
> +       kfree(obj);

> +       if (tmp == ASUSWMI_UNSUPPORTED_METHOD)

This is uninitialized tmp in case when no obj, or obj is of the wrong type.

> +               return -ENODEV;
> +       return 0;
> +#else
> +       return -EOPNOTSUPP;
> +#endif
> +}

...

> +static u16 nct6775_wmi_read_value(struct nct6775_data *data, u16 reg)
> +{
> +       int res, word_sized = is_word_sized(data, reg);
> +       u8 tmp;
> +
> +       nct6775_wmi_set_bank(data, reg);
> +
> +       nct6775_asuswmi_read(data->bank, reg, &tmp);

> +       res = (tmp & 0xff);

Too many parentheses.
tnp is u8, ' & 0xff' is redundant.

> +       if (word_sized) {
> +               nct6775_asuswmi_read(data->bank, (reg & 0xff) + 1, &tmp);
> +               res = (res << 8) + (tmp & 0xff);

Ditto.

> +       }
> +       return res;
> +}
> +
> +static int nct6775_wmi_write_value(struct nct6775_data *data, u16 reg, u16 value)
> +{
> +       int word_sized = is_word_sized(data, reg);
> +
> +       nct6775_wmi_set_bank(data, reg);
> +
> +       if (word_sized) {

> +               nct6775_asuswmi_write(data->bank, (reg & 0xff),

Too many parentheses

> +                                     (value >> 8) & 0xff);

' & 0xff' part is redundant.

> +               nct6775_asuswmi_write(data->bank, (reg & 0xff) + 1,
> +                                     value & 0xff);
> +       } else {
> +               nct6775_asuswmi_write(data->bank, (reg & 0xff), value);
> +       }
> +
> +       return 0;
> +}

...

> +               err = match_string(asus_wmi_boards, ARRAY_SIZE(asus_wmi_boards),
> +                                  board_name);

> +               if (err != -EINVAL) {

I believe I commented on this in the way as

if (err >= 0)

The rationale behind is that you shouldn't really care what kind of
error codes the API may return.

> +                       /* if reading chip id via WMI succeeds, use WMI */
> +                       if (!nct6775_asuswmi_read(0, NCT6775_PORT_CHIPID, &tmp)) {
> +                               pr_info("Using Asus WMI to access %#x chip.\n", tmp);
> +                               access = access_asuswmi;
> +                       } else {
> +                               pr_err("Can't read ChipID by Asus WMI.\n");
> +                       }
> +               }

Guenter Roeck Sept. 16, 2021, 1:21 p.m. UTC | #2

On 9/16/21 1:34 AM, Andy Shevchenko wrote:
> On Wed, Sep 15, 2021 at 11:45 PM Denis Pauk <[e-mail]> wrote:
>>
>> Support accessing the NCT677x via Asus WMI functions.
>>
>> On mainboards that support this way of accessing the chip, the driver will
>> usually not work without this option since in these mainboards, ACPI will
>> mark the I/O port as used.
>>
>> Code uses ACPI firmware interface to commucate with sensors with ASUS
> 
> communicate
> 
>> motherboards:
>> * PRIME B460-PLUS,
>> * ROG CROSSHAIR VIII IMPACT,
>> * ROG STRIX B550-E GAMING,
>> * ROG STRIX B550-F GAMING,
>> * ROG STRIX B550-F GAMING (WI-FI),
>> * ROG STRIX Z490-I GAMING,
>> * TUF GAMING B550M-PLUS,
>> * TUF GAMING B550M-PLUS (WI-FI),
>> * TUF GAMING B550-PLUS,
>> * TUF GAMING X570-PLUS,
>> * TUF GAMING X570-PRO (WI-FI).
> 
> ...
> 
>> +static int asuswmi_evaluate_method(u32 method_id, u8 bank, u8 reg, u8 val, u32 *retval)
>> +{
> 
>> +#if IS_ENABLED(CONFIG_ACPI_WMI)
> 
> The idea behind IS_ENABLED() macro is that it may be used in C
> conditionals, like
> 
> if (IS_ENABLED(...))
> 

It can be and is used either way.

$ git grep "#if IS_ENABLED" | wc
    3126    6529  199841

$ git grep "if (IS_ENABLED" | wc
    1624    6871  120270

>> +       u32 args = bank | (reg << 8) | (val << 16);
>> +       struct acpi_buffer input = { (acpi_size) sizeof(args), &args };
>> +       struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
>> +       acpi_status status;
>> +       union acpi_object *obj;
>> +       u32 tmp = 0;
> 
>> +       obj = output.pointer;
>> +       if (obj && obj->type == ACPI_TYPE_INTEGER)
>> +               tmp = obj->integer.value;
>> +
>> +       if (retval)
>> +               *retval = tmp;
>> +
>> +       kfree(obj);
> 
>> +       if (tmp == ASUSWMI_UNSUPPORTED_METHOD)
> 
> This is uninitialized tmp in case when no obj, or obj is of the wrong type.
> 

In this situation, we know that the ACPI call succeeded. My assumption was
that this code explicitly checks for a specific error code returned from
the ASUS WMI code, which would be returned as integer. This is an additional
error check on top of previous error checks, and it looks perfectly valid to me.

Other WMI code doesn't check for errors other than "if (ACPI_FAILURE(status))".

>> +               return -ENODEV;
>> +       return 0;
>> +#else
>> +       return -EOPNOTSUPP;
>> +#endif
>> +}
> 
> ...
> 
>> +static u16 nct6775_wmi_read_value(struct nct6775_data *data, u16 reg)
>> +{
>> +       int res, word_sized = is_word_sized(data, reg);
>> +       u8 tmp;
>> +
>> +       nct6775_wmi_set_bank(data, reg);
>> +
>> +       nct6775_asuswmi_read(data->bank, reg, &tmp);
> 
>> +       res = (tmp & 0xff);
> 
> Too many parentheses.
> tnp is u8, ' & 0xff' is redundant.
> 
>> +       if (word_sized) {
>> +               nct6775_asuswmi_read(data->bank, (reg & 0xff) + 1, &tmp);
>> +               res = (res << 8) + (tmp & 0xff);
> 
> Ditto.
> 
>> +       }
>> +       return res;
>> +}
>> +
>> +static int nct6775_wmi_write_value(struct nct6775_data *data, u16 reg, u16 value)
>> +{
>> +       int word_sized = is_word_sized(data, reg);
>> +
>> +       nct6775_wmi_set_bank(data, reg);
>> +
>> +       if (word_sized) {
> 
>> +               nct6775_asuswmi_write(data->bank, (reg & 0xff),
> 
> Too many parentheses
> 
>> +                                     (value >> 8) & 0xff);
> 
> ' & 0xff' part is redundant.
> 
>> +               nct6775_asuswmi_write(data->bank, (reg & 0xff) + 1,
>> +                                     value & 0xff);
>> +       } else {
>> +               nct6775_asuswmi_write(data->bank, (reg & 0xff), value);
>> +       }
>> +
>> +       return 0;
>> +}
> 
> ...
> 
>> +               err = match_string(asus_wmi_boards, ARRAY_SIZE(asus_wmi_boards),
>> +                                  board_name);
> 
>> +               if (err != -EINVAL) {
> 
> I believe I commented on this in the way as
> 
> if (err >= 0)
> 
> The rationale behind is that you shouldn't really care what kind of
> error codes the API may return.
> 
>> +                       /* if reading chip id via WMI succeeds, use WMI */
>> +                       if (!nct6775_asuswmi_read(0, NCT6775_PORT_CHIPID, &tmp)) {
>> +                               pr_info("Using Asus WMI to access %#x chip.\n", tmp);
>> +                               access = access_asuswmi;
>> +                       } else {
>> +                               pr_err("Can't read ChipID by Asus WMI.\n");
>> +                       }
>> +               }
>

Guenter Roeck Sept. 16, 2021, 1:23 p.m. UTC | #3

On 9/16/21 1:34 AM, Andy Shevchenko wrote:
[ ... ]

>> +       u32 args = bank | (reg << 8) | (val << 16);
>> +       struct acpi_buffer input = { (acpi_size) sizeof(args), &args };
>> +       struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
>> +       acpi_status status;
>> +       union acpi_object *obj;
>> +       u32 tmp = 0;
> 

Ah, you changed the above to add the initialization.
Without knowing that, your comment below is a bit misleading.

Guenter

>> +       obj = output.pointer;
>> +       if (obj && obj->type == ACPI_TYPE_INTEGER)
>> +               tmp = obj->integer.value;
>> +
>> +       if (retval)
>> +               *retval = tmp;
>> +
>> +       kfree(obj);
> 
>> +       if (tmp == ASUSWMI_UNSUPPORTED_METHOD)
> 
> This is uninitialized tmp in case when no obj, or obj is of the wrong type.
> 
>> +               return -ENODEV;
>> +       return 0;
>> +#else
>> +       return -EOPNOTSUPP;
>> +#endif
>> +}
>

Patch

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index e3675377bc5d..9eefb1014b53 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1423,6 +1423,7 @@  config SENSORS_NCT6683
 config SENSORS_NCT6775
 	tristate "Nuvoton NCT6775F and compatibles"
 	depends on !PPC
+	depends on ACPI_WMI || ACPI_WMI=n
 	select HWMON_VID
 	help
 	  If you say yes here you get support for the hardware monitoring
diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
index 4253eed7f5b0..b577381beb45 100644
--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -55,6 +55,7 @@ 
 #include <linux/dmi.h>
 #include <linux/io.h>
 #include <linux/nospec.h>
+#include <linux/wmi.h>
 #include "lm75.h"
 
 #define USE_ALTERNATE
@@ -132,10 +133,13 @@  MODULE_PARM_DESC(fan_debounce, "Enable debouncing for fan RPM signal");
 #define SIO_ID_MASK		0xFFF8
 
 enum pwm_enable { off, manual, thermal_cruise, speed_cruise, sf3, sf4 };
+enum sensor_access { access_direct, access_asuswmi };
 
 struct nct6775_sio_data {
 	int sioreg;
+	int ld;
 	enum kinds kind;
+	enum sensor_access access;
 
 	/* superio_() callbacks  */
 	void (*sio_outb)(struct nct6775_sio_data *sio_data, int reg, int val);
@@ -145,6 +149,90 @@  struct nct6775_sio_data {
 	void (*sio_exit)(struct nct6775_sio_data *sio_data);
 };
 
+#define ASUSWMI_MGMT2_GUID		"466747A0-70EC-11DE-8A39-0800200C9A66"
+#define ASUSWMI_METHODID_RSIO		0x5253494F
+#define ASUSWMI_METHODID_WSIO		0x5753494F
+#define ASUSWMI_METHODID_RHWM		0x5248574D
+#define ASUSWMI_METHODID_WHWM		0x5748574D
+#define ASUSWMI_UNSUPPORTED_METHOD	0xFFFFFFFE
+
+static int asuswmi_evaluate_method(u32 method_id, u8 bank, u8 reg, u8 val, u32 *retval)
+{
+#if IS_ENABLED(CONFIG_ACPI_WMI)
+	u32 args = bank | (reg << 8) | (val << 16);
+	struct acpi_buffer input = { (acpi_size) sizeof(args), &args };
+	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
+	acpi_status status;
+	union acpi_object *obj;
+	u32 tmp = 0;
+
+	status = wmi_evaluate_method(ASUSWMI_MGMT2_GUID, 0,
+				     method_id, &input, &output);
+
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	obj = output.pointer;
+	if (obj && obj->type == ACPI_TYPE_INTEGER)
+		tmp = obj->integer.value;
+
+	if (retval)
+		*retval = tmp;
+
+	kfree(obj);
+
+	if (tmp == ASUSWMI_UNSUPPORTED_METHOD)
+		return -ENODEV;
+	return 0;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+static inline int nct6775_asuswmi_write(u8 bank, u8 reg, u8 val)
+{
+	return asuswmi_evaluate_method(ASUSWMI_METHODID_WHWM, bank,
+							      reg, val, NULL);
+}
+
+static inline int nct6775_asuswmi_read(u8 bank, u8 reg, u8 *val)
+{
+	u32 tmp;
+	int ret = asuswmi_evaluate_method(ASUSWMI_METHODID_RHWM, bank,
+				     reg, 0, &tmp);
+	*val = tmp;
+	return ret;
+}
+
+static int superio_wmi_inb(struct nct6775_sio_data *sio_data, int reg)
+{
+	int tmp;
+
+	asuswmi_evaluate_method(ASUSWMI_METHODID_RSIO, sio_data->ld,
+				reg, 0, &tmp);
+	return tmp;
+}
+
+static void superio_wmi_outb(struct nct6775_sio_data *sio_data, int reg, int val)
+{
+	asuswmi_evaluate_method(ASUSWMI_METHODID_WSIO, sio_data->ld,
+				reg, val, NULL);
+}
+
+static void superio_wmi_select(struct nct6775_sio_data *sio_data, int ld)
+{
+	sio_data->ld = ld;
+}
+
+static int superio_wmi_enter(struct nct6775_sio_data *sio_data)
+{
+	return 0;
+}
+
+static void superio_wmi_exit(struct nct6775_sio_data *sio_data)
+{
+}
+
 static void superio_outb(struct nct6775_sio_data *sio_data, int reg, int val)
 {
 	int ioreg = sio_data->sioreg;
@@ -207,6 +295,7 @@  static void superio_exit(struct nct6775_sio_data *sio_data)
 
 #define NCT6775_REG_BANK	0x4E
 #define NCT6775_REG_CONFIG	0x40
+#define NCT6775_PORT_CHIPID	0x58
 
 /*
  * Not currently used:
@@ -1423,6 +1512,47 @@  static bool is_word_sized(struct nct6775_data *data, u16 reg)
 	return false;
 }
 
+static inline void nct6775_wmi_set_bank(struct nct6775_data *data, u16 reg)
+{
+	u8 bank = reg >> 8;
+
+	data->bank = bank;
+}
+
+static u16 nct6775_wmi_read_value(struct nct6775_data *data, u16 reg)
+{
+	int res, word_sized = is_word_sized(data, reg);
+	u8 tmp;
+
+	nct6775_wmi_set_bank(data, reg);
+
+	nct6775_asuswmi_read(data->bank, reg, &tmp);
+	res = (tmp & 0xff);
+	if (word_sized) {
+		nct6775_asuswmi_read(data->bank, (reg & 0xff) + 1, &tmp);
+		res = (res << 8) + (tmp & 0xff);
+	}
+	return res;
+}
+
+static int nct6775_wmi_write_value(struct nct6775_data *data, u16 reg, u16 value)
+{
+	int word_sized = is_word_sized(data, reg);
+
+	nct6775_wmi_set_bank(data, reg);
+
+	if (word_sized) {
+		nct6775_asuswmi_write(data->bank, (reg & 0xff),
+				      (value >> 8) & 0xff);
+		nct6775_asuswmi_write(data->bank, (reg & 0xff) + 1,
+				      value & 0xff);
+	} else {
+		nct6775_asuswmi_write(data->bank, (reg & 0xff), value);
+	}
+
+	return 0;
+}
+
 /*
  * On older chips, only registers 0x50-0x5f are banked.
  * On more recent chips, all registers are banked.
@@ -3818,10 +3948,12 @@  static int nct6775_probe(struct platform_device *pdev)
 	struct device *hwmon_dev;
 	int num_attr_groups = 0;
 
-	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
-	if (!devm_request_region(&pdev->dev, res->start, IOREGION_LENGTH,
-				 DRVNAME))
-		return -EBUSY;
+	if (sio_data->access == access_direct) {
+		res = platform_get_resource(pdev, IORESOURCE_IO, 0);
+		if (!devm_request_region(&pdev->dev, res->start, IOREGION_LENGTH,
+					 DRVNAME))
+			return -EBUSY;
+	}
 
 	data = devm_kzalloc(&pdev->dev, sizeof(struct nct6775_data),
 			    GFP_KERNEL);
@@ -3830,9 +3962,16 @@  static int nct6775_probe(struct platform_device *pdev)
 
 	data->kind = sio_data->kind;
 	data->sioreg = sio_data->sioreg;
-	data->addr = res->start;
-	data->read_value = nct6775_read_value;
-	data->write_value = nct6775_write_value;
+
+	if (sio_data->access == access_direct) {
+		data->addr = res->start;
+		data->read_value = nct6775_read_value;
+		data->write_value = nct6775_write_value;
+	} else {
+		data->read_value = nct6775_wmi_read_value;
+		data->write_value = nct6775_wmi_write_value;
+	}
+
 	mutex_init(&data->update_lock);
 	data->name = nct6775_device_names[data->kind];
 	data->bank = 0xff;		/* Force initial bank selection */
@@ -4743,6 +4882,7 @@  static int __init nct6775_find(int sioaddr, struct nct6775_sio_data *sio_data)
 	int err;
 	int addr;
 
+	sio_data->access = access_direct;
 	sio_data->sioreg = sioaddr;
 
 	err = sio_data->sio_enter(sio_data);
@@ -4837,6 +4977,23 @@  static int __init nct6775_find(int sioaddr, struct nct6775_sio_data *sio_data)
  */
 static struct platform_device *pdev[2];
 
+static const char * const asus_wmi_boards[] = {
+	"PRIME B460-PLUS",
+	"ROG CROSSHAIR VIII DARK HERO",
+	"ROG CROSSHAIR VIII HERO",
+	"ROG CROSSHAIR VIII IMPACT",
+	"ROG STRIX B550-E GAMING",
+	"ROG STRIX B550-F GAMING",
+	"ROG STRIX B550-F GAMING (WI-FI)",
+	"ROG STRIX Z490-I GAMING",
+	"TUF GAMING B550M-PLUS",
+	"TUF GAMING B550M-PLUS (WI-FI)",
+	"TUF GAMING B550-PLUS",
+	"TUF GAMING X570-PLUS",
+	"TUF GAMING X570-PLUS (WI-FI)",
+	"TUF GAMING X570-PRO (WI-FI)",
+};
+
 static int __init sensors_nct6775_init(void)
 {
 	int i, err;
@@ -4845,11 +5002,32 @@  static int __init sensors_nct6775_init(void)
 	struct resource res;
 	struct nct6775_sio_data sio_data;
 	int sioaddr[2] = { 0x2e, 0x4e };
+	enum sensor_access access = access_direct;
+	const char *board_vendor, *board_name;
+	u8 tmp;
 
 	err = platform_driver_register(&nct6775_driver);
 	if (err)
 		return err;
 
+	board_vendor = dmi_get_system_info(DMI_BOARD_VENDOR);
+	board_name = dmi_get_system_info(DMI_BOARD_NAME);
+
+	if (board_name && board_vendor &&
+	    !strcmp(board_vendor, "ASUSTeK COMPUTER INC.")) {
+		err = match_string(asus_wmi_boards, ARRAY_SIZE(asus_wmi_boards),
+				   board_name);
+		if (err != -EINVAL) {
+			/* if reading chip id via WMI succeeds, use WMI */
+			if (!nct6775_asuswmi_read(0, NCT6775_PORT_CHIPID, &tmp)) {
+				pr_info("Using Asus WMI to access %#x chip.\n", tmp);
+				access = access_asuswmi;
+			} else {
+				pr_err("Can't read ChipID by Asus WMI.\n");
+			}
+		}
+	}
+
 	/*
 	 * initialize sio_data->kind and sio_data->sioreg.
 	 *
@@ -4870,6 +5048,16 @@  static int __init sensors_nct6775_init(void)
 
 		found = true;
 
+		sio_data.access = access;
+
+		if (access == access_asuswmi) {
+			sio_data.sio_outb = superio_wmi_outb;
+			sio_data.sio_inb = superio_wmi_inb;
+			sio_data.sio_select = superio_wmi_select;
+			sio_data.sio_enter = superio_wmi_enter;
+			sio_data.sio_exit = superio_wmi_exit;
+		}
+
 		pdev[i] = platform_device_alloc(DRVNAME, address);
 		if (!pdev[i]) {
 			err = -ENOMEM;
@@ -4881,23 +5069,25 @@  static int __init sensors_nct6775_init(void)
 		if (err)
 			goto exit_device_put;
 
-		memset(&res, 0, sizeof(res));
-		res.name = DRVNAME;
-		res.start = address + IOREGION_OFFSET;
-		res.end = address + IOREGION_OFFSET + IOREGION_LENGTH - 1;
-		res.flags = IORESOURCE_IO;
+		if (sio_data.access == access_direct) {
+			memset(&res, 0, sizeof(res));
+			res.name = DRVNAME;
+			res.start = address + IOREGION_OFFSET;
+			res.end = address + IOREGION_OFFSET + IOREGION_LENGTH - 1;
+			res.flags = IORESOURCE_IO;
+
+			err = acpi_check_resource_conflict(&res);
+			if (err) {
+				platform_device_put(pdev[i]);
+				pdev[i] = NULL;
+				continue;
+			}
 
-		err = acpi_check_resource_conflict(&res);
-		if (err) {
-			platform_device_put(pdev[i]);
-			pdev[i] = NULL;
-			continue;
+			err = platform_device_add_resources(pdev[i], &res, 1);
+			if (err)
+				goto exit_device_put;
 		}
 
-		err = platform_device_add_resources(pdev[i], &res, 1);
-		if (err)
-			goto exit_device_put;
-
 		/* platform_device_add calls probe() */
 		err = platform_device_add(pdev[i]);
 		if (err)