Re: [PATCH v3 4/4] can: kvaser_usb: Add support for the Usbcan-II family

Marc Kleine-Budde
2015-01-12T12:34:59Z

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On 01/12/2015 01:26 PM, Ahmed S. Darwish wrote:
> On Mon, Jan 12, 2015 at 12:51:49PM +0100, Marc Kleine-Budde wrote:
>> On 01/08/2015 04:19 PM, Ahmed S. Darwish wrote:
>>
>> [...]
>>
>>>>> MODULE_DEVICE_TABLE(usb, kvaser_usb_table);
>>>>> @@ -463,7 +631,18 @@ static int kvaser_usb_get_software_info(struct kvaser_usb *dev)
>>>>> if (err)
>>>>> return err;
>>>>>
>>>>> - dev->fw_version = le32_to_cpu(msg.u.softinfo.fw_version);
>>>>> + switch (dev->family) {
>>>>> + case KVASER_LEAF:
>>>>> + dev->fw_version = le32_to_cpu(msg.u.leaf.softinfo.fw_version);
>>>>> + break;
>>>>> + case KVASER_USBCAN:
>>>>> + dev->fw_version = le32_to_cpu(msg.u.usbcan.softinfo.fw_version);
>>>>> + break;
>>>>> + default:
>>>>> + dev_err(dev->udev->dev.parent,
>>>>> + "Invalid device family (%d)\n", dev->family);
>>>>> + return -EINVAL;
>>>>
>>>> The default case should not happen. I think you can remove it.
>>
>>> It's true, it _should_ never happen. But I only add such checks if
>>> the follow-up code critically depends on a certain `dev->family`
>>> behavior. So it's kind of a defensive check against any possible
>>> bug in driver or memory.
>>>
>>> What do you think?
>>
>> The kernel is full of callback functions, if you have a bit flip there
>> you're in trouble anyways. A bug in the driver (or other parts of the
>> kernel) might overwrite the memory of dev->family, but if this happens,
>> more things will break.
>>
>
> I see. Thanks for the explanation.
>
> Most of them are now removed in latest submission, except two to
> avoid GCC warnings of variables that "may be used uninitialized".

Thanks, I'll look at the code later and try to figure out what gcc's
problem might be.

Marc

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