Re: [PATCH v4 4/4] can: kvaser_usb: Retry first bulk transfer on -ETIMEDOUT

On Sun, Jan 11, 2015 at 09:51:10PM +0100, Marc Kleine-Budde wrote:

On 01/11/2015 09:45 PM, Ahmed S. Darwish wrote:

quoted

From: Ahmed S. Darwish <redacted>

(This is a draft patch, I'm not sure if this fixes the USB
bug or only its psymptom. Feedback from the linux-usb folks
is really appreciated.)

When plugging the Kvaser USB/CAN dongle the first time, everything
works as expected and all of the transfers from and to the USB
device succeeds.

Meanwhile, after unplugging the device and plugging it again, the
first bulk transfer _always_ returns an -ETIMEDOUT. The following
behaviour was observied:

- Setting higher timeout values for the first bulk transfer never
  solved the issue.

- Unloading, then loading, our kvaser_usb module in question
  __always__ solved the issue.

- Checking first bulk transfer status, and retry the transfer
  again in case of an -ETIMEDOUT also __always__ solved the issue.
  This is what the patch below does.

- In the testing done so far, this issue appears only on laptops
  but never on PCs (possibly power related?)

Signed-off-by: Ahmed S. Darwish <redacted>

Does this patch apply apply between 3 and 4? If not, please re-arrange
the series. As this is a bug fix, patches 1, 2 and 4 will go via
net/master, 3 will go via net-next/master.

Since no one complained earlier, I guess this issue only affects
USBCAN devices. That's why I've based it above patch #3: adding
USBCAN hardware support.

Nonetheless, it won't do any harm for the current Leaf-only
driver. So _if_ this is the correct fix, I will update the commit
log, refactor the check into a 'do { } while()' loop, and then
base it above the Leaf-only net/master fixes on patch #1, and #2.

Any feedback on the USB side of things?

Thanks,
Darwish