Am 22.02.2013 20:06, schrieb Greg KH:
> On Fri, Feb 22, 2013 at 07:58:35PM +0100, walter harms wrote:
>>
>>
>> Am 22.02.2013 19:07, schrieb Kumar Amit Mehta:
>>> fix for instances of DMA buffer on stack(being passed to usb_control_msg)
>>> for
>>> the USB-DUXfast Board driver.
>>>
>>> Signed-off-by: Kumar Amit Mehta <gmate.a...@gmail.com>
>>> ---
>>> drivers/staging/comedi/drivers/usbduxfast.c | 30
>>> ++++++++++++++++-----------
>>> 1 file changed, 18 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/staging/comedi/drivers/usbduxfast.c
>>> b/drivers/staging/comedi/drivers/usbduxfast.c
>>> index 4bf5dd0..1ba0e3d 100644
>>> --- a/drivers/staging/comedi/drivers/usbduxfast.c
>>> +++ b/drivers/staging/comedi/drivers/usbduxfast.c
>>> @@ -436,10 +436,14 @@ static void usbduxfastsub_ai_Irq(struct urb *urb)
>>> static int usbduxfastsub_start(struct usbduxfastsub_s *udfs)
>>> {
>>> int ret;
>>> - unsigned char local_transfer_buffer[16];
>>> + unsigned char *local_transfer_buffer;
>>> +
>>> + local_transfer_buffer = kmalloc(1, GFP_KERNEL);
>>> + if (!local_transfer_buffer)
>>> + return -ENOMEM;
>>>
>>> /* 7f92 to zero */
>>> - local_transfer_buffer[0] = 0;
>>> + *local_transfer_buffer = 0;
>>> /* bRequest, "Firmware" */
>>> ret = usb_control_msg(udfs->usbdev, usb_sndctrlpipe(udfs->usbdev, 0),
>>> USBDUXFASTSUB_FIRMWARE,
>>> @@ -450,22 +454,25 @@ static int usbduxfastsub_start(struct usbduxfastsub_s
>>> *udfs)
>>> local_transfer_buffer,
>>> 1, /* Length */
>>> EZTIMEOUT); /* Timeout */
>>> - if (ret < 0) {
>>> + if (ret < 0)
>>> dev_err(&udfs->interface->dev,
>>> "control msg failed (start)\n");
>>> - return ret;
>>> - }
>>>
>>> - return 0;
>>> + kfree(local_transfer_buffer);
>>> + return ret;
>>> }
>>>
>>> static int usbduxfastsub_stop(struct usbduxfastsub_s *udfs)
>>> {
>>> int ret;
>>> - unsigned char local_transfer_buffer[16];
>>> + unsigned char *local_transfer_buffer;
>>> +
>>> + local_transfer_buffer = kmalloc(1, GFP_KERNEL);
>>> + if (!local_transfer_buffer)
>>> + return -ENOMEM;
>>>
>>> /* 7f92 to one */
>>> - local_transfer_buffer[0] = 1;
>>> + *local_transfer_buffer = 1;
>>> /* bRequest, "Firmware" */
>>> ret = usb_control_msg(udfs->usbdev, usb_sndctrlpipe(udfs->usbdev, 0),
>>> USBDUXFASTSUB_FIRMWARE,
>>> @@ -474,13 +481,12 @@ static int usbduxfastsub_stop(struct usbduxfastsub_s
>>> *udfs)
>>> 0x0000, /* Index */
>>> local_transfer_buffer, 1, /* Length */
>>> EZTIMEOUT); /* Timeout */
>>> - if (ret < 0) {
>>> + if (ret < 0)
>>> dev_err(&udfs->interface->dev,
>>> "control msg failed (stop)\n");
>>> - return ret;
>>> - }
>>>
>>> - return 0;
>>> + kfree(local_transfer_buffer);
>>> + return ret;
>>> }
>>>
>>> static int usbduxfastsub_upload(struct usbduxfastsub_s *udfs,
>>
>> mmh, it seems a bit overheat to alloc 1 byte.
>> Could one of the driver maintainers please comment
>> is that realy need ?
>
> Yes it is needed.
>
>> or is it possible to pass one byte
>> in a register ? (aka char/int) without allocating ?
>
> Nope, the USB host controllers must be able to DMA to this memory
> location, so you have to allocate it dynamically, sorry.
>
> thanks,
thx for clarification.
@Kumar Amit Mehta:
Would you mind to add this as comment ? Allocating one byte does not
look clever so maybe will come up with the idea of changing that.
re,
wh
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