Monday, April 14, 2014, 6:41:05 PM, you wrote:
> 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.
Thanks !
Will test and report back later.
--
Sander
> 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;
--
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