Re: can: kvaser_usb: Add support for Kvaser CAN/USB devices

[Olivier Sobrie <olivier@sobrie.be>]

Hello Dan,

On Thu, Nov 19, 2015 at 03:42:19PM +0300, Dan Carpenter wrote:
> Hello Olivier Sobrie,
> 
> The patch 080f40a6fa28: "can: kvaser_usb: Add support for Kvaser
> CAN/USB devices" from Nov 21, 2012, leads to the following static
> checker warning:
> 
> 	drivers/net/can/usb/kvaser_usb.c:949 kvaser_usb_rx_error()
> 	0x08 | 0x18 has 0x08 set on both sides
> 
> drivers/net/can/usb/kvaser_usb.c
>    941          switch (dev->family) {
>    942          case KVASER_LEAF:
>    943                  if (es->leaf.error_factor) {
>    944                          cf->can_id |= CAN_ERR_BUSERROR | CAN_ERR_PROT;
>    945  
>    946                          if (es->leaf.error_factor & M16C_EF_ACKE)
>    947                                  cf->data[3] |= (CAN_ERR_PROT_LOC_ACK);
>    948                          if (es->leaf.error_factor & M16C_EF_CRCE)
>    949                                  cf->data[3] |= (CAN_ERR_PROT_LOC_CRC_SEQ |
>    950                                                  CAN_ERR_PROT_LOC_CRC_DEL);
> 
> CAN_ERR_PROT_LOC_CRC_SEQ is 0x08
> CAN_ERR_PROT_LOC_CRC_DEL is 0x18
> 
> It's weird that the bits overlap.  Was that intentional?  Why isn't it
> enough to just say?:
> 					cf->data[3] |= CAN_ERR_PROT_LOC_CRC_DEL;
> 
> The static checker complains about most places where
> CAN_ERR_PROT_LOC_CRC_SEQ is used.  I see us setting the flag but not I
> don't see where we test for this so I'm not sure.

No it wasn't intentional. I think that it was inspired from other CAN
drivers. I see the same in net/can/c_can/c_can.c and
net/can/m_can/m_can.c. Sorry for the error.
Btw, which static checker are you using?

As suggested by Oliver, I assume we can transform this in
  cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
and fix all the other places where bitwise operations are done
for errors in data[3].

Should I send a patch to fix this? Or do you or someone else plan
to send a patch?

Thanks,

Olivier