On Fri, Feb 17, 2023 at 02:57:02PM +0200, Tomi Valkeinen wrote:
> On 17/02/2023 13:24, Andy Shevchenko wrote:
> > On Fri, Feb 17, 2023 at 08:57:32AM +0200, Tomi Valkeinen wrote:
> > > On 16/02/2023 17:53, Andy Shevchenko wrote:
> > > > On Thu, Feb 16, 2023 at 04:07:39PM +0200, Tomi Valkeinen wrote:
...
> > > > > struct i2c_board_info ser_info = {
> > > > > - .of_node = to_of_node(rxport->remote_fwnode),
> > > > > - .fwnode = rxport->remote_fwnode,
> > > >
> > > > > + .of_node = to_of_node(rxport->ser.fwnode),
> > > > > + .fwnode = rxport->ser.fwnode,
> > > >
> > > > Why do you need to have both?!
> > >
> > > I didn't debug it, but having only fwnode there will break the probing (no
> > > match).
> >
> > This needs to be investigated. The whole fwnode approach, when we have both
> > fwnode and legacy of_node fields in the same data structure, is that fwnode
> > _OR_ of_node initialization is enough, when both are defined the fwnode
> > should take precedence.
> >
> > If your testing is correct (and I have no doubts) it means we have a serious
> > bug lurking somewhere.
>
> Having both defined or only of_node defined works for me.
But of_node is _legacy_ stuff. We should not really consider this option in the
new code.
> Perhaps the issue is that these drivers only add of_match_table, and thus
> having only .fwnode above is not enough.
No, the code should work with fwnode that carrying DT node or another.
The matching table shouldn't affect this either.
> Looking at i2c_device_match(), i2c_of_match_device() only uses of_node, so
> perhaps I would need CONFIG_ACPI for acpi_driver_match_device to do matching
> with of_node? Although I don't see the acpi code using fwnode, just of_node.
> Well, I have to say I have no idea without spending more time on this.
Again, there is a bug and that bug seems nasty one as it would allow to
work the device in one environment and not in another.
Since it's about I²C board files, I believe that an issue is in I²C core.
> > > > > .platform_data = ser_pdata,
> > > > > };
...
> > > > cur_vc = desc.entry[0].bus.csi2.vc;
> > > >
> > > > > + for (i = 0; i < desc.num_entries; ++i) {
> > > > > + u8 vc = desc.entry[i].bus.csi2.vc;
> > > >
> > > > > + if (i == 0) {
> > > > > + cur_vc = vc;
> > > > > + continue;
> > > > > + }
> > > >
> > > > This is an invariant to the loop, see above.
> > >
> > > Well, the current code handles the case of num_entries == 0. I can change it
> > > as you suggest, and first check if num_entries == 0 and also start the loop
> > > from 1.
> >
> > You may try to compile both variants and see which one gets lets code.
> > I believe it will be mine or they are equivalent in case compiler is clever
> > enough to recognize the invariant.
>
> But your suggestion accesses desc.entry[0] even if there are no entries,
> accessing possibly uninitialized memory. In that case it doesn't use it for
> anything, but at least I find that kind of code worrying.
Yes you probably will need a 0 case to be handled separately. I was and
is not objecting this.
> > > > > + if (vc == cur_vc)
> > > > > + continue;
> > > > > +
> > > > > + dev_err(&priv->client->dev,
> > > > > + "rx%u: source with multiple virtual-channels is not supported\n",
> > > > > + nport);
> > > > > + return -ENODEV;
> > > > > + }
...
> > Up to you, but this just a good example why I do not like how optional
> > properties are handled in a "smart" way.
> >
> > To me
> >
> > foo = DEFAULT;
> > _property_read_(&foo); // no error checking
> >
> > is clean, neat, small and good enough solution.
>
> Yes, if you have a default. I don't.
It can't be true. If you have an optional property you always have a default
even if you are not using it (let's call it special case).
foo_present = property_present();
property_read(&foo_val);
...
if (foo_present) {
// do something with foo_val
}
The boolean variable is needed when the range of the foo_val takes all possible
values of the type (u32?). Otherwise you always can define a magic that will
tell you "okay, this is not in use". Of course having boolean always is also
fine.
> I could add a new magic number for the
> eq_level which means not-defined and use it as a default, but I don't
> usually like default values which are not 0. Here I have the manual_eq
> boolean to tell if we're using manual EQ or not.
Oh, this is similar that I described above.
But as I said, you can keep your initial version, it's up to you and
maintainers to cope with that (uglification).
--
With Best Regards,
Andy Shevchenko
