On Sat, 1 Jun 2019 at 21:57, Jakub Kicinski
<jakub.kicinski@xxxxxxxxxxxxx> wrote:
>
> On Fri, 31 May 2019 19:18:17 +0000, Saeed Mahameed wrote:
> > > + if (!bpf_op || flags & XDP_FLAGS_SKB_MODE)
> > > + mode = XDP_FLAGS_SKB_MODE;
> > > +
> > > + curr_mode = dev_xdp_current_mode(dev);
> > > +
> > > + if (!offload && curr_mode && (mode ^ curr_mode) &
> > > + (XDP_FLAGS_DRV_MODE | XDP_FLAGS_SKB_MODE)) {
> >
> > if i am reading this correctly this is equivalent to :
> >
> > if (!offload && (curre_mode != mode))
> > offlad is false then curr_mode and mode must be DRV or GENERIC ..
>
> Naw, if curr_mode is not set, i.e. nothing installed now, we don't care
> about the diff.
>
> > better if you keep bitwise operations for actual bitmasks, mode and
> > curr_mode are not bitmask, they can hold one value each .. according to
> > your logic..
>
> Well, they hold one bit each, whether one bit is a bitmap perhaps is
> disputable? :)
>
> I think the logic is fine.
>
Hmm, but changing to:
if (!offload && curr_mode && mode != curr_mode)
is equal, and to Saeed's point, clearer. I'll go that route in a v3.
> What happened to my request to move the change in behaviour for
> disabling to a separate patch, tho, Bjorn? :)
Actually, I left that out completely. This patch doesn't change the
behavior. After I realized how the flags *should* be used, I don't
think my v1 change makes sense anymore. My v1 patch was to give an
error if you tried to disable, say generic if drv was enabled via
"auto detect/no flags". But this is catched by looking at the flags.
What I did, however, was moving the flags check into change_fd so that
the driver doesn't have to do the check. E.g. the Intel drivers didn't
do correct checking of flags.
