On Tue, 2016-05-10 at 11:24 +0000, David Laight wrote:
> From: Ben Hutchings
> >
> > Sent: 09 May 2016 01:17
> > On Sun, 2016-05-08 at 13:55 -0700, Shrikrishna Khare wrote:
> > >
> > >
> > > On Sat, 7 May 2016, Ben Hutchings wrote:
> > >
> > > >
> > > > On Fri, 2016-05-06 at 16:12 -0700, Shrikrishna Khare wrote:
> > > > [...]
> > > > >
> > > > > +static int
> > > > > +vmxnet3_set_coalesce(struct net_device *netdev, struct
> > > > > ethtool_coalesce *ec)
> > > > > +{
> > > > [...]
> > > > >
> > > > > + switch (ec->rx_coalesce_usecs) {
> > > > > + case VMXNET3_COALESCE_DEFAULT:
> > > > > + case VMXNET3_COALESCE_DISABLED:
> > > > > + case VMXNET3_COALESCE_ADAPT:
> > > > > + if (ec->tx_max_coalesced_frames ||
> > > > > + ec->tx_max_coalesced_frames_irq ||
> > > > > + ec->rx_max_coalesced_frames_irq) {
> > > > > + return -EINVAL;
> > > > > + }
> > > > > + memset(adapter->coal_conf, 0,
> > > > > sizeof(*adapter->coal_conf));
> > > > > + adapter->coal_conf->coalMode = ec->rx_coalesce_usecs;
> > > > > + break;
> > > > > + case VMXNET3_COALESCE_STATIC:
> > > > [...]
> > > >
> > > > I don't want to see drivers introducing magic values for fields that
> > > > are denominated in microseconds (especially not for 0, which is the
> > > > correct way to specify 'no coalescing'). If the current
> > > > ethtool_coalesce structure is inadequate, propose an extension.
> > > For vmxnet3, we need an ethtool mechanism to indicate coalescing mode to
> > > the device.
> > >
> > > Would a patch that maps 0 to 'no coalescing' be acceptable? That is:
> > >
> > > rx-usecs = 0 -> coalescing disabled.
> > > rx-usecs = 1 -> default (chosen by the device).
> > > rx-usecs = 2 -> adaptive coalescing.
> > > rx-usecs = 3 -> static coalescing.
> Would it be better to use stupidly large values for the non-zero special
> values?
> That would less problematic if someone expects 2 to mean '2 usecs'.That seems less problematic, but I think we'd have to check that current drivers (or at least the most widely used ones) reject those values. We should still need to standardise names and definitions for those special values, so that the ethtool utility can provide keywords and documentation for them. Ben. -- Ben Hutchings If you seem to know what you are doing, you'll be given more to do.
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