Re: [PATCH] IRQ: ease out-of-tree migration to new irq_handler prototype

[William D Waddington]

Alexey Dobriyan wrote:
> On Sat, Nov 04, 2006 at 12:06:53PM -0800, William D Waddington wrote:
>
> > Alexey Dobriyan wrote:
> >
> > > On Sat, Nov 04, 2006 at 10:29:37AM -0800, William D Waddington wrote:
> > >
> > >
> > > > Ease out-of-tree driver migration to new irq_handler prototype.
> > > > Define empty 3rd argument macro for use in multi kernel version
> > > > out-of-tree drivers going forward.  Backportable drives can do:
> > > >
> > > > (in a header)
> > > > #ifndef __PT_REGS
> > > > # define __PT_REGS , struct pt_regs *regs
> > > > #endif
> > >
> > >
> > > Backportable drivers should check kernel version themselves and define
> > > __PT_REGS themselves.
> >
> > I think I provided too much information :(  It would be sufficiently
> > helpful to just #define __PT_REGS <nothing> in  interrupt.h to make
> > things easier for low-life out-of-tree maintainers.  There isn't any
> > need to actualy detect version.  Just detect __PT_REGS already defined.
>
>
> Out-of-tree maintainer will have to change his code ANYWAY. And while he
> is doing that, he can spend 10 seconds to add 5-line version check.

I'm a little out of my depth here (obviously) but why is it "better" to
require a version check rather than the kernel simply flagging the
function change?  Rather like HAVE_COMPAT_IOCTL.

With the proposed 1-line kernel patch my drivers build against kernels
back to 2.6.9 (the earliest I have around here) without any version
checking.

> More, if you've followed pt_regs removal patches, you'd noticed that
> some of them were not trivial. In this case version check is least of
> his worries.

Ah. I don't use the *regs arg.  The one line patch just keeps the
compiler happy. And provides a "tidy" way to detect the interface
change if necessary.

> > The "in a header" above referred to the driver's header - #ifdefs in
> > executable code really looks nasty IMHO.
> >
> > The "#define __PT_REGS , ..." comment below was intended to be a
> > "helpful" note to driver writers.  Like I said, TMI.
> >
> >
> > > > (in code body)
> > > > static irqreturn_t irq_handler(int irq, void *dev_id __PT_REGS)
> > >
> > >
> > > > +/*
> > > > + * Irq handler migration helper - empty 3rd argument
> > > > + * #define __PT_REGS , struct pt_regs *regs
> > > > + * for older kernel versions
> > > > + */
> > > > +
> > > > +#define __PT_REGS
> >
> > How should I tidy this up - if it is acceptable at all?
>
>
> No, this is not acceptable.

Oh well.

Thanks for your time,
Bill
--
--------------------------------------------
William D Waddington
Bainbridge Island, WA, USA
william.waddington@xxxxxxxxxx
--------------------------------------------
"Even bugs...are unexpected signposts on
the long road of creativity..." - Ken Burtch
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