Via Velocity minimum MTU size

[Dave Jones]

On Sun, May 21, 2006 at 02:43:24PM -0500, Jay Cliburn wrote:
 > I'm trying to set the MTU size on my Via Velocity 6122 Gbit adapter from
 > the default of 1500 down to 1492, but I keep getting this error:
 > 
 > [root at osprey ~]# ifconfig eth0 mtu 1492
 > SIOCSIFMTU: Invalid argument
 > 
 > Turns out that via-velocity.h defines the minimum MTU at 1500 bytes.
 > 
 > #define VELOCITY_MIN_MTU    (1514-14)
 > #define VELOCITY_MAX_MTU    (9000)
 > 
 > And via-velocity.c enforces the limit.
 > 
 >     if ((new_mtu < VELOCITY_MIN_MTU) || new_mtu > (VELOCITY_MAX_MTU)) {
 >          VELOCITY_PRT(MSG_LEVEL_ERR, KERN_NOTICE "%s: Invalid MTU.\n",
 >                                 vptr->dev->name);
 >          return -EINVAL;
 >     }
 > 
 > This is an Abit AV8 motherboard with an Athlon64 3000+ cpu running
 > 2.6.16-1.2111_FC5 x86_64.
 > 
 > Can someone explain why the driver might constrain the NIC to a minimum
 > MTU size of 1500?

Asking the developers on netdev at vger.kernel.org is going to get
you the answer faster than asking here.

		Dave

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