Currently stk1160_read_reg() uses a stack-allocated char to get the
read control value. This is wrong because usb_control_msg() requires
a kmalloc-ed buffer, and a DMA-API warning is produced:
WARNING: CPU: 0 PID: 1376 at lib/dma-debug.c:1153 check_for_stack+0xa0/0x100()
ehci-pci 0000:00:0a.0: DMA-API: device driver maps memory fromstack [addr=ffff88003d0b56bf]
This commit fixes such issue by using a 'usb_ctrl_read' field embedded
in the device's struct to pass the value. In addition, we introduce a
mutex to protect the value.
While here, let's remove the urb_buf array which was meant for a similar
purpose, but never really used.
Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@xxxxxxxxxxxxxxxxxx>
---
Sander, Hans:
Does this cause any regressions, other than the DMA-API warning?
In that case, we can consider this as suitable for -stable.
drivers/media/usb/stk1160/stk1160-core.c | 8 +++++++-
drivers/media/usb/stk1160/stk1160.h | 3 ++-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/media/usb/stk1160/stk1160-core.c b/drivers/media/usb/stk1160/stk1160-core.c
index 34a26e0..cce91e7 100644
--- a/drivers/media/usb/stk1160/stk1160-core.c
+++ b/drivers/media/usb/stk1160/stk1160-core.c
@@ -69,15 +69,20 @@ int stk1160_read_reg(struct stk1160 *dev, u16 reg, u8 *value)
int pipe = usb_rcvctrlpipe(dev->udev, 0);
*value = 0;
+
+ mutex_lock(&dev->urb_ctrl_lock);
ret = usb_control_msg(dev->udev, pipe, 0x00,
USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
- 0x00, reg, value, sizeof(u8), HZ);
+ 0x00, reg, &dev->urb_ctrl_read, sizeof(u8), HZ);
if (ret < 0) {
stk1160_err("read failed on reg 0x%x (%d)\n",
reg, ret);
+ mutex_unlock(&dev->urb_ctrl_lock);
return ret;
}
+ *value = dev->urb_ctrl_read;
+ mutex_unlock(&dev->urb_ctrl_lock);
return 0;
}
@@ -322,6 +327,7 @@ static int stk1160_probe(struct usb_interface *interface,
* because we register the device node as the *last* thing.
*/
spin_lock_init(&dev->buf_lock);
+ mutex_init(&dev->urb_ctrl_lock);
mutex_init(&dev->v4l_lock);
mutex_init(&dev->vb_queue_lock);
diff --git a/drivers/media/usb/stk1160/stk1160.h b/drivers/media/usb/stk1160/stk1160.h
index 05b05b1..8886be4 100644
--- a/drivers/media/usb/stk1160/stk1160.h
+++ b/drivers/media/usb/stk1160/stk1160.h
@@ -143,7 +143,7 @@ struct stk1160 {
int num_alt;
struct stk1160_isoc_ctl isoc_ctl;
- char urb_buf[255]; /* urb control msg buffer */
+ char urb_ctrl_read;
/* frame properties */
int width; /* current frame width */
@@ -159,6 +159,7 @@ struct stk1160 {
struct i2c_adapter i2c_adap;
struct i2c_client i2c_client;
+ struct mutex urb_ctrl_lock; /* protects urb_ctrl_read */
struct mutex v4l_lock;
struct mutex vb_queue_lock;
spinlock_t buf_lock;
--
1.9.1
--
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