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Re: [PATCH RFC 07/77] PCI/MSI: Re-design MSI/MSI-X interrupts enablement

To: Alexander Gordeev <agordeev@redhat.com>
Subject: Re: [PATCH RFC 07/77] PCI/MSI: Re-design MSI/MSI-X interrupts enablement pattern
From: Tejun Heo <tj@kernel.org>
Date: Wed, 9 Oct 2013 11:54:13 -0400
Cc: linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>, Ralf Baechle <ralf@linux-mips.org>, Michael Ellerman <michael@ellerman.id.au>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Ingo Molnar <mingo@redhat.com>, Dan Williams <dan.j.williams@intel.com>, Andy King <acking@vmware.com>, Jon Mason <jon.mason@intel.com>, Matt Porter <mporter@kernel.crashing.org>, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux390@de.ibm.com, linux-s390@vger.kernel.org, x86@kernel.org, linux-ide@vger.kernel.org, iss_storagedev@hp.com, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, netdev@vger.kernel.org, e1000-devel@lists.sourceforge.net, linux-driver@qlogic.com, Solarflare linux maintainers <linux-net-drivers@solarflare.com>, "VMware, Inc." <pv-drivers@vmware.com>, linux-scsi@vger.kernel.org
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Hello, Alexander.

On Tue, Oct 08, 2013 at 09:48:26AM +0200, Alexander Gordeev wrote:
> > If there are many which duplicate the above pattern, it'd probably be
> > worthwhile to provide a helper?  It's usually a good idea to reduce
> > the amount of boilerplate code in drivers.
> 
> I wanted to limit discussion in v1 to as little changes as possible.
> I 'planned' those helper(s) for a separate effort if/when the most
> important change is accepted and soaked a bit.

The thing is doing it this way generates more churns and noises.  Once
the simpler ones live behind a wrapper which can be built on the
existing interface, we can have both reduced cost and more latitude on
the complex cases.

> > If we do things this way, it breaks all drivers using this interface
> > until they're converted, right?
> 
> Right. And the rest of the series does it.

Which breaks bisection which we shouldn't do.

> > Also, it probably isn't the best idea
> > to flip the behavior like this as this can go completely unnoticed (no
> > compiler warning or anything, the same function just behaves
> > differently).  Maybe it'd be a better idea to introduce a simpler
> > interface that most can be converted to?
> 
> Well, an *other* interface is a good idea. What do you mean with the
> simpler here?

I'm still talking about a simpler wrapper for common cases, which is
the important part anyway.

Thanks.

-- 
tejun

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