linux-kernel - Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi

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Date:	Tue, 18 Nov 2014 22:15:05 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	"Yun Wu (Abel)" <wuyun.wu@...wei.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Grant Likely <grant.likely@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Yijing Wang <wangyijing@...wei.com>
Subject: Re: [patch 08/16] genirq: Introduce callback irq_chip.irq_write_msi_msg


On 2014/11/18 22:03, Jiang Liu wrote:
> On 2014/11/18 21:52, Yun Wu (Abel) wrote:
>> On 2014/11/18 21:43, Jiang Liu wrote:
>>
>>> On 2014/11/18 21:33, Yun Wu (Abel) wrote:
>>> Hi Yun,
>>> 	We provide an irq_chip for each type of interrupt controller
>>> instead of devices. For the example mentioned above, if device A
>>> and Group B has different interrupt controllers, we just need to
>>> implement irq_chip_A and irq_chip_B and set irq_chip.irq_write_msi_msg()
>>> to suitable callbacks.
>>> 	The framework already achieves what you you want:)
>>
>> What if device A and group B have the same interrupt controller?
> Device doesn't care about interrupt controllers, it just cares about
> interrupts used by itself. It's the interrupt source (controller)
> enumerators' responsibility to discover interrupt source, associate
> methods to control the interrupt source and assign irq numbers for
> interrupt sources.
> There are two ways to associate irq numbers with device:
> 1) arch code/bus drivers statically assigns irq number for devices
>    when creating device objects, such as PCI legacy interrupt
>    (INTA-INTD), IOAPIC interrupts.
> 2) device drivers ask interrupt source enumerators to dynamically
>    create irq numbers, such pci_enable_msix_range() and friends.
> So device driver definitely doesn't need to known about irq_chip
> methods to control interrupt sources.
Please refer to
http://www.xisanqi.net/year/2014/pdf/2014-pdf-09-reconstruct-x86-interrupt-architecture.pdf
for more information
about the hierarchy irqdomain background:)

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