linux-kernel - Re: [PATCH v2 03/22] MSI: Remove the redundant irq_set_chip

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Date:	Fri, 26 Sep 2014 10:09:22 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Yijing Wang <wangyijing@...wei.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Xinwei Hu <huxinwei@...wei.com>,
	Wuyun <wuyun.wu@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	linux-arch@...r.kernel.org, arnab.basu@...escale.com,
	Bharat.Bhushan@...escale.com, x86@...nel.org,
	Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	xen-devel@...ts.xenproject.org, Joerg Roedel <joro@...tes.org>,
	iommu@...ts.linux-foundation.org, linux-mips@...ux-mips.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	Tony Luck <tony.luck@...el.com>, linux-ia64@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org, Chris Metcalf <cmetcalf@...era.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Lucas Stach <l.stach@...gutronix.de>,
	David Vrabel <david.vrabel@...rix.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: Re: [PATCH v2 03/22] MSI: Remove the redundant irq_set_chip_data()

On Fri, Sep 26, 2014 at 10:04:45AM +0800, Yijing Wang wrote:
> On 2014/9/25 15:19, Thierry Reding wrote:
> > On Thu, Sep 25, 2014 at 11:14:13AM +0800, Yijing Wang wrote:
> >> Currently, pcie-designware, pcie-rcar, pci-tegra drivers
> >> use irq chip_data to save the msi_chip pointer. They
> >> already call irq_set_chip_data() in their own MSI irq map
> >> functions. So irq_set_chip_data() in arch_setup_msi_irq()
> >> is useless.
> > 
> > Again, I think this should be the other way around. If drivers do
> > something that's already handled by the core, then the duplicate code
> > should be dropped from the drivers.
> 
> Hi Thierry, this is different thing, because chip_data is specific to IRQ
> controller, and in other platform, like in x86, chip_data is used to save irq_cfg.
> So we can not call irq_set_chip_data() in core code.
> 
> x86 irq piece code
> 
> int arch_setup_hwirq(unsigned int irq, int node)
> {
> 	struct irq_cfg *cfg;
> 	unsigned long flags;
> 	int ret;
> 
> 	cfg = alloc_irq_cfg(irq, node);
> 	if (!cfg)
> 		return -ENOMEM;
> 
> 	raw_spin_lock_irqsave(&vector_lock, flags);
> 	ret = __assign_irq_vector(irq, cfg, apic->target_cpus());
> 	raw_spin_unlock_irqrestore(&vector_lock, flags);
> 
> 	if (!ret)
> 		irq_set_chip_data(irq, cfg);  ------------->Save irq_cfg
> 	else
> 		free_irq_cfg(irq, cfg);
> 	return ret;
> }

Okay, makes sense to keep irq_set_chip_data() for driver-specific data
then.

Thierry

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