Re: [RFC 02/14] virtio: use eth_link_read/write (and bug fix)

[Stephen Hemminger <stephen@networkplumber.org>]

On Sun, 16 Jul 2017 15:33:26 +0300
Andrew Rybchenko <arybchenko@solarflare.com> wrote:

> > +	link.link_autoneg = ETH_LINK_SPEED_FIXED;  
> 
> As I understand link_autoneg is 1 bit field with boolean semantics. I.e. 0/false - no autoneg, 1/true - autoneg.
> It looks like it has wrong comment:
>          uint16_t link_autoneg : 1;  /**< ETH_LINK_SPEED_[AUTONEG/FIXED] */
> 
> since
> #define ETH_LINK_SPEED_AUTONEG  (0 <<  0)  /**< Autonegotiate (all speeds) */
> #define ETH_LINK_SPEED_FIXED    (1 <<  0)  /**< Disable autoneg (fixed speed) */
> 
> whereas
> #define ETH_LINK_FIXED          0 /**< No autonegotiation. */
> #define ETH_LINK_AUTONEG        1 /**< Autonegotiated. */
> 
> In general this attempt to introduce bug is the result of wrong comment which is caused by very similar
> defines with opposite values.

Orignal observation was because some drivers (vmxnet3) were setting autoneg = fixed
and others were not. Turns out it makes no difference 
since FIXED == 0, the old code and new code have same effect.