Re: Need clarity on MSI handling in RC driver

[valmiki <valmikibow@gmail.com>]

Thanks Marc

On 1/4/2017 11:16 PM, Marc Zyngier wrote:
> On 04/01/17 17:39, valmiki wrote:
>> Hi All,
>>
>> I have a doubt, the MSI domains are handled differently in different RC
>> drivers.
>>
>> Some drivers use irq_domain_add_linear alone, and some use
>> pci_msi_create_irq_domain also to handle MSI.
>>
>> In most of the 32-bit architectures only irq_domain_add_linear is used
>> and in 64 bit drivers both pci_msi_create_irq_domain and
>> irq_domain_add_linear are used.
>>
>> So is this because of architecture difference between ARM and ARM64 ?
>
> Neither. This is purely a software construct. Newer drivers use the
> generic MSI infrastructure (which also allows things like non-PCI MSI),
> while older drivers use some ad-hoc infrastructure which is more or less
> specific to PCI.
>
> The former is the way to go, and the latter is being phased out.
>
> I'll let Mark draw some shiny ASCII art.
>
> Thanks,
>
> 	M.
>