fsi: Miscellaneous fixes and I2C Responder driver

Since we have two scom drivers, use the standard of matching if the driver specifies a table so that the right devices go to the right driver.

Signed-off-by Eddie James <[email protected]>

---
 drivers/fsi/fsi-core.c | 11 +++++++++--
 drivers/fsi/fsi-scom.c |  8 ++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

drivers/fsi/fsi-core.c +9 -2

index b77013b9d8a7..ca4a9634fbc3 100644
@@ -16,6 +16,7 @@
 #include <linux/idr.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
 #include <linux/cdev.h>

@@ -1375,8 +1376,14 @@ static int fsi_bus_match(struct device *dev, struct device_driver *drv)
 		if (id->engine_type != fsi_dev->engine_type)
 			continue;
 		if (id->version == FSI_VERSION_ANY ||
-				id->version == fsi_dev->version)
-			return 1;
+		    id->version == fsi_dev->version) {
+			if (drv->of_match_table) {
+				if (of_driver_match_device(dev, drv))
+					return 1;
+			} else {
+				return 1;
+			}
+		}
 	}
 
 	return 0;

drivers/fsi/fsi-scom.c +1 -0

index bcb756dc9866..61dbda9dbe2b 100644
@@ -10,6 +10,7 @@
 #include <linux/cdev.h>
 #include <linux/delay.h>
 #include <linux/fs.h>
+#include <linux/mod_devicetable.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
 #include <linux/list.h>

Master indexing is problematic if a hub is rescanned while the root master is being rescanned. Move the IDA free below the device unregistration, lock the scan mutex in the probe function, and request a specific idx in the hub driver.

Signed-off-by Eddie James <[email protected]>

---
 drivers/fsi/fsi-core.c       | 41 ++++++++++++++++++++++--------------
 drivers/fsi/fsi-master-hub.c |  2 ++
 2 files changed, 27 insertions(+), 16 deletions(-)

drivers/fsi/fsi-core.c +0 -0

index ec4d02264391..503061a6740b 100644

drivers/fsi/fsi-core.c +3 -1

        if (master->idx < 0)
                return master->idx;
 
 
-       dev_set_name(&master->dev, "fsi%d", master->idx);
+       if (!dev_name(&master->dev))
+               dev_set_name(&master->dev, "fsi%d", master->idx);
+

drivers/fsi/fsi-core.c +9 -11

-       np = dev_of_node(&master->dev);
-       if (!of_property_read_bool(np, "no-scan-on-init")) {
-               mutex_lock(&master->scan_lock);
-               fsi_master_scan(master);
-               mutex_unlock(&master->scan_lock);
+               if (!of_property_read_bool(np, "no-scan-on-init"))
+                       fsi_master_scan(master);
        }
 
-       return 0;
+       mutex_unlock(&master->scan_lock);
+       return rc;
 }
 EXPORT_SYMBOL_GPL(fsi_master_register);
 
 void fsi_master_unregister(struct fsi_master *master)
 {
-       trace_fsi_master_unregister(master);
+       int idx = master->idx;
 
-       if (master->idx >= 0) {
-               ida_free(&master_ida, master->idx);
-               master->idx = -1;
-       }
+       trace_fsi_master_unregister(master);
 
        mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
+       master->n_links = 0;
        mutex_unlock(&master->scan_lock);
+
        device_unregister(&master->dev);
+       ida_free(&master_ida, idx);
 }
 EXPORT_SYMBOL_GPL(fsi_master_unregister);
 

drivers/fsi/fsi-master-hub.c +2 -1

index 6d8b6e8854e5..36da643b3201 100644
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 
 #include "fsi-master.h"
+#include "fsi-slave.h"
 
 #define FSI_ENGID_HUB_MASTER           0x1c
 

@@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
        hub->master.dev.release = hub_master_release;
        hub->master.dev.of_node = of_node_get(dev_of_node(dev));
 
+       hub->master.idx = fsi_dev->slave->link + 1;
        hub->master.n_links = links;
        hub->master.read = hub_master_read;
        hub->master.write = hub_master_write;
--

2.31.1

Quoted 5 lines · Eddie James

Master indexing is problematic if a hub is rescanned while the root master is being rescanned. Move the IDA free below the device unregistration, lock the scan mutex in the probe function, and request a specific idx in the hub driver.

I've applied this series, but taking a closer look at this patch I think it can be improved. If you resend, just send this patch.

Quoted 13 lines

Signed-off-by Eddie James <[email protected]>

---
 drivers/fsi/fsi-core.c       | 41 ++++++++++++++++++++++--------------
 drivers/fsi/fsi-master-hub.c |  2 ++
 2 files changed, 27 insertions(+), 16 deletions(-)

drivers/fsi/fsi-core.c +0 -0

index ec4d02264391..503061a6740b 100644

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1333

Quoted 9 lines

drivers/fsi/fsi-core.c +2 -2

@@ -1327,46 +1327,55 @@ static struct class fsi_master_class = {
 int fsi_master_register(struct fsi_master *master)
 {
        int rc;
-       struct device_node *np;
 
        mutex_init(&master->scan_lock);
-       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+
+       if (master->idx) {

Why do we allocate a new idx if there's already one?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1335

Quoted 2 lines

drivers/fsi/fsi-core.c +2 -0

+               master->idx = ida_alloc_range(&master_ida, master->idx,
+                                             master->idx, GFP_KERNEL);

If we can't get one in the range we want, we ask for any? Should this print a warning?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1338

Quoted 3 lines

drivers/fsi/fsi-core.c +3 -0

+               if (master->idx < 0)
+                       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       } else {

If ixd was zero, we create one. This is the "normal" case?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1341

Quoted 3 lines

drivers/fsi/fsi-core.c +3 -0

+               master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       }
+

We check the same error condition again.

Quoted 8 lines

drivers/fsi/fsi-core.c +3 -1

        if (master->idx < 0)
                return master->idx;
 
 
-       dev_set_name(&master->dev, "fsi%d", master->idx);
+       if (!dev_name(&master->dev))
+               dev_set_name(&master->dev, "fsi%d", master->idx);
+

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1355

Quoted 10 lines

drivers/fsi/fsi-core.c +3 -2

        master->dev.class = &fsi_master_class;
 
+       mutex_lock(&master->scan_lock);
        rc = device_register(&master->dev);
        if (rc) {
                ida_free(&master_ida, master->idx);
-               return rc;
-       }
+       } else {
+               struct device_node *np = dev_of_node(&master->dev);

This change looks a bit different to the idx changes. What's happening here?

Quoted 60 lines

drivers/fsi/fsi-core.c +9 -11

-       np = dev_of_node(&master->dev);
-       if (!of_property_read_bool(np, "no-scan-on-init")) {
-               mutex_lock(&master->scan_lock);
-               fsi_master_scan(master);
-               mutex_unlock(&master->scan_lock);
+               if (!of_property_read_bool(np, "no-scan-on-init"))
+                       fsi_master_scan(master);
        }
 
-       return 0;
+       mutex_unlock(&master->scan_lock);
+       return rc;
 }
 EXPORT_SYMBOL_GPL(fsi_master_register);
 
 void fsi_master_unregister(struct fsi_master *master)
 {
-       trace_fsi_master_unregister(master);
+       int idx = master->idx;
 
-       if (master->idx >= 0) {
-               ida_free(&master_ida, master->idx);
-               master->idx = -1;
-       }
+       trace_fsi_master_unregister(master);
 
        mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
+       master->n_links = 0;
        mutex_unlock(&master->scan_lock);
+
        device_unregister(&master->dev);
+       ida_free(&master_ida, idx);
 }
 EXPORT_SYMBOL_GPL(fsi_master_unregister);
 

drivers/fsi/fsi-master-hub.c +2 -1

index 6d8b6e8854e5..36da643b3201 100644
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 
 #include "fsi-master.h"
+#include "fsi-slave.h"
 
 #define FSI_ENGID_HUB_MASTER           0x1c
 

@@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
        hub->master.dev.release = hub_master_release;
        hub->master.dev.of_node = of_node_get(dev_of_node(dev));
 
+       hub->master.idx = fsi_dev->slave->link + 1;
        hub->master.n_links = links;
        hub->master.read = hub_master_read;
        hub->master.write = hub_master_write;
--

2.31.1

Quoted 7 lines · Joel Stanley

Quoted 4 lines · Eddie James

Master indexing is problematic if a hub is rescanned while the root master is being rescanned. Move the IDA free below the device unregistration, lock the scan mutex in the probe function, and request a specific idx in the hub driver.

I've applied this series, but taking a closer look at this patch I think it can be improved. If you resend, just send this patch.

On hardware, it did this at FSI scan time:

  WARNING: CPU: 0 PID: 761 at /lib/idr.c:525 ida_free+0x140/0x154
  ida_free called for id=1 which is not allocated.
  CPU: 0 PID: 761 Comm: openpower-proc- Not tainted 6.1.34-d42f59e #1
  Hardware name: Generic DT based system
   unwind_backtrace from show_stack+0x18/0x1c
   show_stack from dump_stack_lvl+0x24/0x2c
   dump_stack_lvl from __warn+0x74/0xf0
   __warn from warn_slowpath_fmt+0x9c/0xd8
   warn_slowpath_fmt from ida_free+0x140/0x154
   ida_free from fsi_master_register+0xd0/0xf0
   fsi_master_register from hub_master_probe+0x11c/0x358
   hub_master_probe from really_probe+0xd4/0x3f0
   really_probe from driver_probe_device+0x38/0xd0
   driver_probe_device from __device_attach_driver+0xc8/0x148
   __device_attach_driver from bus_for_each_drv+0x90/0xdc
   bus_for_each_drv from __device_attach+0x114/0x1a4
   __device_attach from bus_probe_device+0x8c/0x94
   bus_probe_device from device_add+0x3a8/0x7fc
   device_add from fsi_master_scan+0x4e0/0x950
   fsi_master_scan from fsi_master_rescan+0x38/0x88
   fsi_master_rescan from master_rescan_store+0x14/0x20
   master_rescan_store from kernfs_fop_write_iter+0x114/0x200
   kernfs_fop_write_iter from vfs_write+0x1d0/0x374
   vfs_write from ksys_write+0x78/0x100
   ksys_write from ret_fast_syscall+0x0/0x54
  Exception stack(0x9fc51fa8 to 0x9fc51ff0)
  1fa0:                   00000001 01a01c78 00000003 01a01c78 00000001 00000001
  1fc0: 00000001 01a01c78 00000001 00000004 7eeb4ab0 7eeb4b3c 7eeb4ab4 7eeb499c
  1fe0: 76985abc 7eeb4928 76848af8 766f176c

Quoted 113 lines

Quoted 11 lines

Signed-off-by Eddie James <[email protected]>

---
  drivers/fsi/fsi-core.c       | 41 ++++++++++++++++++++++--------------
  drivers/fsi/fsi-master-hub.c |  2 ++
  2 files changed, 27 insertions(+), 16 deletions(-)

drivers/fsi/fsi-core.c +0 -0

index ec4d02264391..503061a6740b 100644

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1333

Quoted 9 lines

drivers/fsi/fsi-core.c +2 -2

@@ -1327,46 +1327,55 @@ static struct class fsi_master_class = {
  int fsi_master_register(struct fsi_master *master)
  {
         int rc;
-       struct device_node *np;
 
         mutex_init(&master->scan_lock);
-       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+
+       if (master->idx) {

Why do we allocate a new idx if there's already one?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1335

Quoted 2 lines

drivers/fsi/fsi-core.c +2 -0

+               master->idx = ida_alloc_range(&master_ida, master->idx,
+                                             master->idx, GFP_KERNEL);

If we can't get one in the range we want, we ask for any? Should this print a warning?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1338

Quoted 3 lines

drivers/fsi/fsi-core.c +3 -0

+               if (master->idx < 0)
+                       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       } else {

If ixd was zero, we create one. This is the "normal" case?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1341

Quoted 3 lines

drivers/fsi/fsi-core.c +3 -0

+               master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       }
+

We check the same error condition again.

Quoted 6 lines

drivers/fsi/fsi-core.c +3 -1

         if (master->idx < 0)
                 return master->idx;
-       dev_set_name(&master->dev, "fsi%d", master->idx);
+       if (!dev_name(&master->dev))
+               dev_set_name(&master->dev, "fsi%d", master->idx);
+

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1355

Quoted 10 lines

drivers/fsi/fsi-core.c +3 -2

         master->dev.class = &fsi_master_class;
 
+       mutex_lock(&master->scan_lock);
         rc = device_register(&master->dev);
         if (rc) {
                 ida_free(&master_ida, master->idx);
-               return rc;
-       }
+       } else {
+               struct device_node *np = dev_of_node(&master->dev);

This change looks a bit different to the idx changes. What's happening here?

Quoted 59 lines

drivers/fsi/fsi-core.c +9 -11

-       np = dev_of_node(&master->dev);
-       if (!of_property_read_bool(np, "no-scan-on-init")) {
-               mutex_lock(&master->scan_lock);
-               fsi_master_scan(master);
-               mutex_unlock(&master->scan_lock);
+               if (!of_property_read_bool(np, "no-scan-on-init"))
+                       fsi_master_scan(master);
         }
 
-       return 0;
+       mutex_unlock(&master->scan_lock);
+       return rc;
  }
  EXPORT_SYMBOL_GPL(fsi_master_register);
 
  void fsi_master_unregister(struct fsi_master *master)
  {
-       trace_fsi_master_unregister(master);
+       int idx = master->idx;
 
-       if (master->idx >= 0) {
-               ida_free(&master_ida, master->idx);
-               master->idx = -1;
-       }
+       trace_fsi_master_unregister(master);
 
         mutex_lock(&master->scan_lock);
         fsi_master_unscan(master);
+       master->n_links = 0;
         mutex_unlock(&master->scan_lock);
+
         device_unregister(&master->dev);
+       ida_free(&master_ida, idx);
  }
  EXPORT_SYMBOL_GPL(fsi_master_unregister);
 

drivers/fsi/fsi-master-hub.c +2 -1

index 6d8b6e8854e5..36da643b3201 100644
@@ -12,6 +12,7 @@
  #include <linux/slab.h>
 
  #include "fsi-master.h"
+#include "fsi-slave.h"
 
  #define FSI_ENGID_HUB_MASTER           0x1c
 

@@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
         hub->master.dev.release = hub_master_release;
         hub->master.dev.of_node = of_node_get(dev_of_node(dev));
 
+       hub->master.idx = fsi_dev->slave->link + 1;
         hub->master.n_links = links;
         hub->master.read = hub_master_read;
         hub->master.write = hub_master_write;
--

2.31.1

Quoted 4 lines · Eddie James

Master indexing is problematic if a hub is rescanned while the root master is being rescanned. Move the IDA free below the device unregistration, lock the scan mutex in the probe function, and request a specific idx in the hub driver.

I've applied this series, but taking a closer look at this patch I think it can be improved. If you resend, just send this patch.

Quoted 16 lines

Signed-off-by Eddie James <[email protected]>

---
  drivers/fsi/fsi-core.c       | 41 ++++++++++++++++++++++--------------
  drivers/fsi/fsi-master-hub.c |  2 ++
  2 files changed, 27 insertions(+), 16 deletions(-)

drivers/fsi/fsi-core.c +0 -1

index ec4d02264391..503061a6740b 100644
@@ -1327,46 +1327,55 @@ static struct class fsi_master_class = {
  int fsi_master_register(struct fsi_master *master)
  {
         int rc;
-       struct device_node *np;
 

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1333

Quoted 4 lines

drivers/fsi/fsi-core.c +2 -1

         mutex_init(&master->scan_lock);
-       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+
+       if (master->idx) {

Why do we allocate a new idx if there's already one?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1335

Quoted 3 lines

drivers/fsi/fsi-core.c +2 -0

+               master->idx = ida_alloc_range(&master_ida, master->idx,
+                                             master->idx, GFP_KERNEL);

If we can't get one in the range we want, we ask for any? Should this print a warning?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1338

Quoted 4 lines

drivers/fsi/fsi-core.c +3 -0

+               if (master->idx < 0)
+                       master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       } else {

If ixd was zero, we create one. This is the "normal" case?

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1341

Quoted 4 lines

drivers/fsi/fsi-core.c +3 -0

+               master->idx = ida_alloc(&master_ida, GFP_KERNEL);
+       }
+

We check the same error condition again.

Quoted 7 lines

drivers/fsi/fsi-core.c +3 -1

         if (master->idx < 0)
                 return master->idx;
-       dev_set_name(&master->dev, "fsi%d", master->idx);
+       if (!dev_name(&master->dev))
+               dev_set_name(&master->dev, "fsi%d", master->idx);
+

drivers/fsi/fsi-core.c static struct class fsi_master_class = { · line 1355

Quoted 10 lines

drivers/fsi/fsi-core.c +3 -2

         master->dev.class = &fsi_master_class;
 
+       mutex_lock(&master->scan_lock);
         rc = device_register(&master->dev);
         if (rc) {
                 ida_free(&master_ida, master->idx);
-               return rc;
-       }
+       } else {
+               struct device_node *np = dev_of_node(&master->dev);

This change looks a bit different to the idx changes. What's happening here?

Quoted 59 lines

drivers/fsi/fsi-core.c +9 -11

-       np = dev_of_node(&master->dev);
-       if (!of_property_read_bool(np, "no-scan-on-init")) {
-               mutex_lock(&master->scan_lock);
-               fsi_master_scan(master);
-               mutex_unlock(&master->scan_lock);
+               if (!of_property_read_bool(np, "no-scan-on-init"))
+                       fsi_master_scan(master);
         }
 
-       return 0;
+       mutex_unlock(&master->scan_lock);
+       return rc;
  }
  EXPORT_SYMBOL_GPL(fsi_master_register);
 
  void fsi_master_unregister(struct fsi_master *master)
  {
-       trace_fsi_master_unregister(master);
+       int idx = master->idx;
 
-       if (master->idx >= 0) {
-               ida_free(&master_ida, master->idx);
-               master->idx = -1;
-       }
+       trace_fsi_master_unregister(master);
 
         mutex_lock(&master->scan_lock);
         fsi_master_unscan(master);
+       master->n_links = 0;
         mutex_unlock(&master->scan_lock);
+
         device_unregister(&master->dev);
+       ida_free(&master_ida, idx);
  }
  EXPORT_SYMBOL_GPL(fsi_master_unregister);
 

drivers/fsi/fsi-master-hub.c +2 -1

index 6d8b6e8854e5..36da643b3201 100644
@@ -12,6 +12,7 @@
  #include <linux/slab.h>
 
  #include "fsi-master.h"
+#include "fsi-slave.h"
 
  #define FSI_ENGID_HUB_MASTER           0x1c
 

@@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
         hub->master.dev.release = hub_master_release;
         hub->master.dev.of_node = of_node_get(dev_of_node(dev));
 
+       hub->master.idx = fsi_dev->slave->link + 1;
         hub->master.n_links = links;
         hub->master.read = hub_master_read;
         hub->master.write = hub_master_write;
--

2.31.1

The I2CR has the capability to directly perform SCOM operations, circumventing the need to drive the FSI2PIB engine. Add a new driver to perform SCOM operations through the I2CR.

Signed-off-by Eddie James <[email protected]>

---
 drivers/fsi/Kconfig     |   8 +++
 drivers/fsi/Makefile    |   1 +
 drivers/fsi/i2cr-scom.c | 154 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+)
 create mode 100644 drivers/fsi/i2cr-scom.c

drivers/fsi/Kconfig +8 -0

index 999be82720c5..79a31593618a 100644
@@ -94,4 +94,12 @@ config FSI_OCC
 	provide the raw sensor data as well as perform thermal and power
 	management on the system.
 
+config I2CR_SCOM
+	tristate "IBM I2C Responder SCOM driver"
+	depends on FSI_MASTER_I2CR
+	help
+	  This option enables an I2C Responder based SCOM device driver. The
+	  I2CR has the capability to directly perform SCOM operations instead
+	  of using the FSI2PIB engine.
+
 endif

drivers/fsi/Makefile +1 -0

index 34dbaa1c452e..5550aa15e0b1 100644
@@ -9,3 +9,4 @@ obj-$(CONFIG_FSI_MASTER_AST_CF) += fsi-master-ast-cf.o
 obj-$(CONFIG_FSI_SCOM) += fsi-scom.o
 obj-$(CONFIG_FSI_SBEFIFO) += fsi-sbefifo.o
 obj-$(CONFIG_FSI_OCC) += fsi-occ.o
+obj-$(CONFIG_I2CR_SCOM) += i2cr-scom.o

drivers/fsi/i2cr-scom.c new file +119 -0

new file mode 100644
index 000000000000..cb7e02213032
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) IBM Corporation 2023 */
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/fsi.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+
+#include "fsi-master-i2cr.h"
+#include "fsi-slave.h"
+
+struct i2cr_scom {
+	struct device dev;
+	struct cdev cdev;
+	struct fsi_master_i2cr *i2cr;
+};
+
+static loff_t i2cr_scom_llseek(struct file *file, loff_t offset, int whence)
+{
+	switch (whence) {
+	case SEEK_CUR:
+		break;
+	case SEEK_SET:
+		file->f_pos = offset;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return offset;
+}
+
+static ssize_t i2cr_scom_read(struct file *filep, char __user *buf, size_t len, loff_t *offset)
+{
+	struct i2cr_scom *scom = filep->private_data;
+	u64 data;
+	int ret;
+
+	if (len != sizeof(data))
+		return -EINVAL;
+
+	ret = fsi_master_i2cr_read(scom->i2cr, (u32)*offset, &data);
+	if (ret)
+		return ret;
+
+	ret = copy_to_user(buf, &data, len);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t i2cr_scom_write(struct file *filep, const char __user *buf, size_t len,
+			       loff_t *offset)
+{
+	struct i2cr_scom *scom = filep->private_data;
+	u64 data;
+	int ret;
+
+	if (len != sizeof(data))
+		return -EINVAL;
+
+	ret = copy_from_user(&data, buf, len);
+	if (ret)
+		return ret;
+
+	ret = fsi_master_i2cr_write(scom->i2cr, (u32)*offset, data);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static const struct file_operations i2cr_scom_fops = {
+	.owner		= THIS_MODULE,
+	.open		= simple_open,
+	.llseek		= i2cr_scom_llseek,
+	.read		= i2cr_scom_read,
+	.write		= i2cr_scom_write,
+};
+
+static int i2cr_scom_probe(struct device *dev)
+{
+	struct fsi_device *fsi_dev = to_fsi_dev(dev);
+	struct i2cr_scom *scom;
+	int didx;
+	int ret;
+
+	if (!is_fsi_master_i2cr(fsi_dev->slave->master))
+		return -ENODEV;
+
+	scom = devm_kzalloc(dev, sizeof(*scom), GFP_KERNEL);
+	if (!scom)
+		return -ENOMEM;
+
+	scom->i2cr = to_fsi_master_i2cr(fsi_dev->slave->master);
+	dev_set_drvdata(dev, scom);
+
+	scom->dev.type = &fsi_cdev_type;
+	scom->dev.parent = dev;
+	device_initialize(&scom->dev);
+
+	ret = fsi_get_new_minor(fsi_dev, fsi_dev_scom, &scom->dev.devt, &didx);
+	if (ret)
+		return ret;
+
+	dev_set_name(&scom->dev, "scom%d", didx);
+	cdev_init(&scom->cdev, &i2cr_scom_fops);
+	ret = cdev_device_add(&scom->cdev, &scom->dev);
+	if (ret)
+		fsi_free_minor(scom->dev.devt);
+
+	return ret;
+}
+
+static int i2cr_scom_remove(struct device *dev)
+{