[PATCH] mfd: viperboard: allocate I/O buffer separately

[Octavian Purdila]

Currently the I/O buffer is allocated part of the device status
structure, potentially sharing the same cache line with other members
in this structure.

Allocate the buffer separately, to avoid the I/O operations corrupting
the device status structure due to cache line sharing.

Compiled tested only, as I don't have access to hardware.

Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx>
---
 drivers/mfd/viperboard.c       | 16 ++++++++++------
 include/linux/mfd/viperboard.h |  2 +-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c
index e00f534..d27c131 100644
--- a/drivers/mfd/viperboard.c
+++ b/drivers/mfd/viperboard.c
@@ -59,9 +59,13 @@ static int vprbrd_probe(struct usb_interface *interface,
 
 	/* allocate memory for our device state and initialize it */
 	vb = kzalloc(sizeof(*vb), GFP_KERNEL);
-	if (vb == NULL) {
-		dev_err(&interface->dev, "Out of memory\n");
+	if (vb == NULL)
 		return -ENOMEM;
+
+	vb->buf = kzalloc(sizeof(struct vprbrd_i2c_write_msg), GFP_KERNEL);
+	if (vb->buf == NULL) {
+		ret = -ENOMEM;
+		goto error;
 	}
 
 	mutex_init(&vb->lock);
@@ -103,10 +107,9 @@ static int vprbrd_probe(struct usb_interface *interface,
 	return 0;
 
 error:
-	if (vb) {
-		usb_put_dev(vb->usb_dev);
-		kfree(vb);
-	}
+	usb_put_dev(vb->usb_dev);
+	kfree(vb->buf);
+	kfree(vb);
 
 	return ret;
 }
@@ -118,6 +121,7 @@ static void vprbrd_disconnect(struct usb_interface *interface)
 	mfd_remove_devices(&interface->dev);
 	usb_set_intfdata(interface, NULL);
 	usb_put_dev(vb->usb_dev);
+	kfree(vb->buf);
 	kfree(vb);
 
 	dev_dbg(&interface->dev, "disconnected\n");
diff --git a/include/linux/mfd/viperboard.h b/include/linux/mfd/viperboard.h
index 1934528..af928d0 100644
--- a/include/linux/mfd/viperboard.h
+++ b/include/linux/mfd/viperboard.h
@@ -103,7 +103,7 @@ struct vprbrd_i2c_addr_msg {
 struct vprbrd {
 	struct usb_device *usb_dev; /* the usb device for this device */
 	struct mutex lock;
-	u8 buf[sizeof(struct vprbrd_i2c_write_msg)];
+	u8 *buf;
 	struct platform_device pdev;
 };
 
-- 
1.9.1

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