Re: [Intel-wired-lan] [net-next] igb: add function to set I210 transmit mode

On 16-08-13 08:27 AM, Alexander Duyck wrote:

On Tue, Aug 9, 2016 at 11:48 PM, Gangfeng [off-list ref] wrote:

quoted

From: Gangfeng Huang <redacted>

I210 supports two transmit modes, legacy and Qav. The transmit mode is
configured in TQAVCTRL.QavMode register. Before this patch igb driver
only support legacy mode. This patch makes it possible to configure the
transmit mode.

Example:
Get the transmit mode:
$ echo /sys/class/net/eth0/qav_mode
0
Set transmit mode to qav mode
$ echo 1 > /sys/class/net/eth0/qav_mode

Tested:
Setting /sys/class/net/eth0/qav_mode to Qav mode,
 1) Switch back and forth between Qav mode and legacy mode
 2) Send/recv packets in both mode.

Signed-off-by: Gangfeng Huang <redacted>

I really don' think this patch is going to work.  If you are going to
implement something like this and have a hope to get it accepted into
the Linux kernel you need to come up with a solution that will work
fore more than this one device.  We don't want the drivers having to
carry around their own sysfs controls for things that really are not
proprietary to the device.  There needs to be a generic kernel
interface for this.  The fact is something like QAV more than likely
exists on other devices as well so it may be worth while to look into
seeing if you could come up with some way of interfacing this with
either ethtool ,iproute2, or maybe even the DCB/LLDP utilities since
this is essentially splitting the Tx into two separate traffic
classes.

Also for these kind of patches it would be best to include the netdev
mailing list.  That way it can be reviewed by a wider audience and you
are much more likely to get this accepted upstream rather than have it
rejected when Jeff Kirsher attempts to submit it.

Take a look at ./net/sched/sch_mqprio.c and the ndo op setup_tc.
Multiple folks have been talking about adding support for this and
I think a lot of the bits you need might be there.

.John