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Subject[PATCH] i2c: i2c-tiny-usb: fix buffer not being DMA capable
Date
The i2c-tiny-usb driver generates the following trace and fails to
read or write data on a v4.9 or newer kernels. This patch avoids the
problem by allocating a DMA capable buffer for data transfer.

[ 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 ]---

Cc: <stable@vger.kernel.org> # Kernel 4.9+
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
---
drivers/i2c/busses/i2c-tiny-usb.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tiny-usb.c b/drivers/i2c/busses/i2c-tiny-usb.c
index 0ed77eeff31e..ca30a1a93d29 100644
--- a/drivers/i2c/busses/i2c-tiny-usb.c
+++ b/drivers/i2c/busses/i2c-tiny-usb.c
@@ -178,22 +178,33 @@ static int usb_read(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 = kmalloc(len, GFP_KERNEL);
+ int ret;

/* 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;

/* 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)
--
2.11.0
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