On Tue, Sep 28, 2021 at 08:52:17AM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 28, 2021 at 05:12:39PM +0800, Mark Zhang wrote:
> > On 9/28/2021 1:30 AM, Jason Gunthorpe wrote:
> > > On Wed, Sep 15, 2021 at 02:07:25AM +0300, Leon Romanovsky wrote:
> > > > +static int stat_get_doit_default_counter(struct sk_buff *skb,
> > > > + struct nlmsghdr *nlh,
> > > > + struct netlink_ext_ack *extack,
> > > > + struct nlattr *tb[])
> > > > +{
> > > > + struct rdma_hw_stats *stats;
> > > > + struct ib_device *device;
> > > > + u32 index, port;
> > > > + int ret;
> > > > +
> > > > + if (!tb[RDMA_NLDEV_ATTR_DEV_INDEX] || !tb[RDMA_NLDEV_ATTR_PORT_INDEX])
> > > > + return -EINVAL;
> > > > +
> > > > + index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
> > > > + device = ib_device_get_by_index(sock_net(skb->sk), index);
> > > > + if (!device)
> > > > + return -EINVAL;
> > > > +
> > > > + port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
> > > > + if (!rdma_is_port_valid(device, port)) {
> > > > + ret = -EINVAL;
> > > > + goto end;
> > > > + }
> > > > +
> > > > + stats = ib_get_hw_stats_port(device, port);
> > > > + if (!stats) {
> > > > + ret = -EINVAL;
> > > > + goto end;
> > > > + }
> > > > +
> > > > + if (tb[RDMA_NLDEV_ATTR_STAT_HWCOUNTER_DYNAMIC])
> > > > + ret = stat_get_doit_stats_list(skb, nlh, extack, tb,
> > > > + device, port, stats);
> > > > + else
> > > > + ret = stat_get_doit_stats_values(skb, nlh, extack, tb, device,
> > > > + port, stats);
> > >
> > > This seems strange, why is the output of a get contingent on a ignored
> > > input attribute? Shouldn't the HWCOUNTER_DYNAMIC just always be
> > > emitted?
> >
> > The CMD_STAT_GET is originally used to get the default hwcounter statistic
> > (the value of all hwstats), now we also want to use this command to get a
> > list of counters (just name and status), so kernel differentiates these 2
> > cases based on HWCOUNTER_DYNAMIC attr.
>
> Don't do that, it is not how netlink works. Either the whole attribute
> should be returned or you need a new get command
The netlink way is to be independent on returned parameter, if it not
supported, this parameter won't be available at all. This makes HWCOUNTER_DYNAMIC
to work exactly as netlink would do.
Thanks
>
> Jason
