Re: [PATCH v4 3/4] can: kvaser_usb: Add support for the Usbcan-II family

Marc Kleine-Budde
2015-01-18T20:14:18Z

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On 01/18/2015 09:12 PM, Ahmed S. Darwish wrote:
> Hi!
>
> On Mon, Jan 12, 2015 at 02:53:02PM +0100, Olivier Sobrie wrote:
>> Hello,
>>
>> On Sun, Jan 11, 2015 at 03:36:12PM -0500, Ahmed S. Darwish wrote:
>>> From: Ahmed S. Darwish <ahmed.darwish@valeo.com>
>>>
>
> ...
>
>>> @@ -98,7 +128,13 @@
>>> #define CMD_START_CHIP_REPLY 27
>>> #define CMD_STOP_CHIP 28
>>> #define CMD_STOP_CHIP_REPLY 29
>>> -#define CMD_GET_CARD_INFO2 32
>>> +#define CMD_READ_CLOCK 30
>>> +#define CMD_READ_CLOCK_REPLY 31
>>
>> These two defines are not used.
>>
>
> They were added for completeness: the only gap in our continuous
> sequence of command IDs from 12 to 39 ;-) No big deal, to be
> removed in the next submission.
>
> ...
>
>>> +
>>> +struct kvaser_msg_tx_acknowledge_header {
>>> + u8 channel;
>>> + u8 tid;
>>> +};
>>
>> Is this struct really needed? Can't you simply use
>> leaf_msg_tx_acknowledge or usbcan_msg_tx_acknowledge
>> structures to read the header.
>> Same for kvaser_msg_rx_can_header.
>>
>
> They're added to ensure type-safety throughout the code. Basically
> they're the common part of a command that has different wire format
> between the Leaf and the USBCan, but share a common header. Such
> notation was only added when it was strictly necessary.
>
> For example, there are three functions where 'rx_can_header' is
> referenced in the driver, and one function where 'tx_acknowledge_header'
> is referenced. Without such header structure, I'll have to sprinkle
> 3 to 4 extra blocks of:
>
> switch (dev->family) {
> case KVASER_LEAF:
> case KVASER_USBCAN:
> }
>
> which would be _really_ ugly. The *_header notation ensures that, in
> the body of each function, we're accessing the fields in a very safe
> manner.

+1 Keep it as it is.

Marc

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