Re: [RFC PATCH 01/13] PCI: Prepare removing devres from pci_intx()

Philipp Stanner
2024-10-14T09:12:11Z

On Fri, 2024-10-11 at 16:50 +0300, Andy Shevchenko wrote:
> On Fri, Oct 11, 2024 at 02:16:06PM +0200, Philipp Stanner wrote:
> > On Thu, 2024-10-10 at 17:40 +0300, Andy Shevchenko wrote:
> > > On Wed, Oct 09, 2024 at 10:35:07AM +0200, Philipp Stanner wrote:
> > > > pci_intx() is a hybrid function which sometimes performs devres
> > > > operations, depending on whether pcim_enable_device() has been
> > > > used
> > > > to
> > > > enable the pci_dev. This sometimes-managed nature of the
> > > > function
> > > > is
> > > > problematic. Notably, it causes the function to allocate under
> > > > some
> > > > circumstances which makes it unusable from interrupt context.
> > > >
> > > > To, ultimately, remove the hybrid nature from pci_intx(), it is
> > > > first
> > > > necessary to provide an always-managed and a never-managed
> > > > version
> > > > of that function. Then, all callers of pci_intx() can be ported
> > > > to
> > > > the
> > > > version they need, depending whether they use
> > > > pci_enable_device()
> > > > or
> > > > pcim_enable_device().
>
> > > > An always-managed function exists, namely pcim_intx(), for
> > > > which
> > > > __pcim_intx(), a never-managed version of pci_intx() had been
> > > > implemented.
> > >
> > > > Make __pcim_intx() a public function under the name
> > > > pci_intx_unmanaged(). Make pcim_intx() a public function.
>
> It seems I got confused by these two paragraphs. Why the double
> underscored
> function is even mentioned here?

It's mentioned because it's being moved.

>
> > > To avoid an additional churn we can make just completely new
> > > APIs,
> > > namely:
> > > pcim_int_x()
> > > pci_int_x()
> > >
> > > You won't need all dirty dances with double underscored function
> > > naming and
> > > renaming.
> >
> > Ähm.. I can't follow. The new version doesn't use double
> > underscores
> > anymore. __pcim_intx() is being removed, effectively.
> > After this series, we'd end up with a clean:
> >
> > pci_intx() <-> pcim_intx()
> >
> > just as in the other PCI APIs.
>
> ...
>
> > > > + pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
> > > > +
> > > > + if (enable)
> > > > + new = pci_command & ~PCI_COMMAND_INTX_DISABLE;
> > > > + else
> > > > + new = pci_command | PCI_COMMAND_INTX_DISABLE;
> > > > +
> > > > + if (new != pci_command)
> > >
> > > I would use positive conditionals as easy to read (yes, a couple
> > > of
> > > lines
> > > longer, but also a win is the indentation and avoiding an
> > > additional
> > > churn in
> > > the future in case we need to add something in this branch.
> >
> > I can't follow. You mean:
> >
> > if (new == pci_command)
> >     return;
> >
> > ?
> >
> > That's exactly the same level of indentation.
>
> No, the body gets one level off.
>
> > Plus, I just copied the code.
> >
> > > > + pci_write_config_word(pdev, PCI_COMMAND, new);
>
> if (new == pci_command)
> return;
>
> pci_write_config_word(pdev, PCI_COMMAND, new);
>
> See the difference?
> Also, imaging adding a new code in your case:
>
> if (new != pci_command)
> pci_write_config_word(pdev, PCI_COMMAND, new);
>
> ==>
>
> if (new != pci_command) {
> ...foo...
> pci_write_config_word(pdev, PCI_COMMAND, new);
> ...bar...
> }
>
> And in mine:
>
> if (new == pci_command)
> return;
>
> ...foo...
> pci_write_config_word(pdev, PCI_COMMAND, new);
> ...bar...
>
> I hope it's clear now what I meant.

It is clear.. I'm not necessarily convinced that it's better to review
than just copying the pre-existing code, but if you really want it we
can do it I guess.

P.