[PATCH 3.16 077/233] i2c: i2c-tiny-usb: fix buffer not being DMA capable

[Ben Hutchings]

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>

commit 5165da5923d6c7df6f2927b0113b2e4d9288661e upstream.

Since v4.9 i2c-tiny-usb generates the below call trace
and longer works, since it can't communicate with the
USB device. The reason is, that since v4.9 the USB
stack checks, that the buffer it should transfer is DMA
capable. This was a requirement since v2.2 days, but it
usually worked nevertheless.

[   17.504959] ------------[ cut here ]------------
[   17.505488] WARNING: CPU: 0 PID: 93 at drivers/usb/core/hcd.c:1587 usb_hcd_map_urb_for_dma+0x37c/0x570
[   17.506545] transfer buffer not dma capable
[   17.507022] Modules linked in:
[   17.507370] CPU: 0 PID: 93 Comm: i2cdetect Not tainted 4.11.0-rc8+ #10
[   17.508103] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   17.509039] Call Trace:
[   17.509320]  ? dump_stack+0x5c/0x78
[   17.509714]  ? __warn+0xbe/0xe0
[   17.510073]  ? warn_slowpath_fmt+0x5a/0x80
[   17.510532]  ? nommu_map_sg+0xb0/0xb0
[   17.510949]  ? usb_hcd_map_urb_for_dma+0x37c/0x570
[   17.511482]  ? usb_hcd_submit_urb+0x336/0xab0
[   17.511976]  ? wait_for_completion_timeout+0x12f/0x1a0
[   17.512549]  ? wait_for_completion_timeout+0x65/0x1a0
[   17.513125]  ? usb_start_wait_urb+0x65/0x160
[   17.513604]  ? usb_control_msg+0xdc/0x130
[   17.514061]  ? usb_xfer+0xa4/0x2a0
[   17.514445]  ? __i2c_transfer+0x108/0x3c0
[   17.514899]  ? i2c_transfer+0x57/0xb0
[   17.515310]  ? i2c_smbus_xfer_emulated+0x12f/0x590
[   17.515851]  ? _raw_spin_unlock_irqrestore+0x11/0x20
[   17.516408]  ? i2c_smbus_xfer+0x125/0x330
[   17.516876]  ? i2c_smbus_xfer+0x125/0x330
[   17.517329]  ? i2cdev_ioctl_smbus+0x1c1/0x2b0
[   17.517824]  ? i2cdev_ioctl+0x75/0x1c0
[   17.518248]  ? do_vfs_ioctl+0x9f/0x600
[   17.518671]  ? vfs_write+0x144/0x190
[   17.519078]  ? SyS_ioctl+0x74/0x80
[   17.519463]  ? entry_SYSCALL_64_fastpath+0x1e/0xad
[   17.519959] ---[ end trace d047c04982f5ac50 ]---

Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Acked-by: Till Harbaum <till@xxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-tiny-usb.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

--- a/drivers/i2c/busses/i2c-tiny-usb.c
+++ b/drivers/i2c/busses/i2c-tiny-usb.c
@@ -178,22 +178,39 @@ static int usb_read(struct i2c_adapter *
 		    int value, int index, void *data, int len)
 {
 	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
+	void *dmadata = kmalloc(len, GFP_KERNEL);
+	int ret;
+
+	if (!dmadata)
+		return -ENOMEM;
 
 	/* do control transfer */
-	return usb_control_msg(dev->usb_dev, usb_rcvctrlpipe(dev->usb_dev, 0),
+	ret = usb_control_msg(dev->usb_dev, usb_rcvctrlpipe(dev->usb_dev, 0),
 			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
-			       USB_DIR_IN, value, index, data, len, 2000);
+			       USB_DIR_IN, value, index, dmadata, len, 2000);
+
+	memcpy(data, dmadata, len);
+	kfree(dmadata);
+	return ret;
 }
 
 static int usb_write(struct i2c_adapter *adapter, int cmd,
 		     int value, int index, void *data, int len)
 {
 	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
+	void *dmadata = kmemdup(data, len, GFP_KERNEL);
+	int ret;
+
+	if (!dmadata)
+		return -ENOMEM;
 
 	/* do control transfer */
-	return usb_control_msg(dev->usb_dev, usb_sndctrlpipe(dev->usb_dev, 0),
+	ret = usb_control_msg(dev->usb_dev, usb_sndctrlpipe(dev->usb_dev, 0),
 			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
-			       value, index, data, len, 2000);
+			       value, index, dmadata, len, 2000);
+
+	kfree(dmadata);
+	return ret;
 }
 
 static void i2c_tiny_usb_free(struct i2c_tiny_usb *dev)