linux-kernel - Re: [PATCH 00/33] dyn_array and nr

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Date:	Wed, 06 Aug 2008 10:37:54 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/33] dyn_array and nr_irqs support v4

Yinghai Lu <yhlu.kernel@...il.com> writes:

> Please check dyn_array support for x86
> v3: split changing to nr_irqs to small patches
>     fix checkpatch error
>     reorder the patch sequence to make dyn_array support go at first
>         so could use that with arrays other than NR_IRQS
> v4: add CONFIG_HAVE_SPARSE_IRQ with list to use condensed irq_desc array
>     so could use 32 init, and init more if needed.
>
> now: x86 32bit: have CONFIG_HAVE_DYN_ARRAY
>      x86 64bit: have CONFIG_HAVE_DYN_ARRAY and CONFIG_HAVE_SPARSE_IRQ
>
> left:
> a. hook irq_2_iommu to irq_desc ?
> b. expand /proc/interrupts to process > nr_irqs
> c. expand to use irq > nr_irqs for msi
>
> notes: may break some arch compling...

It looks like you might possibly be iterating to something usable.
Breaking architectures is not acceptable however.

My suggestion for a non-breaking path:
- Kill NR_IRQS in then generic code.
  With Alan's serial patch and my kstat patch it looks like we have
  the worst of that.

- Introduce get_irq_desc and the functions or function modifications
  that pass a struct irq_desc * into the genirq code.

  Although I absolutely hate the name get_irq_desc as it implies we are
  reference counting something and need a corresponding put_irq_desc.
  Since the lifetime rules don't require that.  Please just call the
  function irq_desc().

- Update arch/x86 to do everything interesting with irq_desc pointers.

- Start dynamically allocating irq_desc and irq_cfg.

Eric

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