On 2014/11/19 17:20, Marc Zyngier wrote: > On Wed, Nov 19 2014 at 6:57:25 am GMT, "Yun Wu (Abel)" <wuyun...@huawei.com> > wrote: >> On 2014/11/18 22:32, Thomas Gleixner wrote: >> >>> On Tue, 18 Nov 2014, Yun Wu (Abel) wrote: >>> >>> Can you please trim the messages when you're replying? >>> >>>> The above you described is absolutely right, but not the things I want >>>> to know. :) >>>> Take GICv3 ITS for example, it deals with both PCI and non PCI message >>>> interrupts. IIUC, several irq_chips need to be implemented in the ITS >>>> driver (i.e. pci_msi_chip, A_msi_chip and B_msi_chip). What should we >>>> do to the ITS driver if new MSI-capable devices come out? >>> >>> You seem to miss the stacking here >>> >>> PCI-MSI -> >>> A-MSI -> ITS -> GIC >>> B-MSI -> >>> >>> So each of the device types has its own MSI controller. Each of them >>> will have their own callbacks and are backed by the underlying ITS/GIC >>> implementation. >> >> Yes, this hits the key point. Once a new device type becomes available, >> we need to add pieces of code outside the new device's driver to make >> it work, which in my opinion is due to lack of core infrastructure. >> More specifically, the core infrastructure needs to support mechanism >> of MSI, not the various types of devices. >> >>> >>> And that's the only sensible solution. >>> >> >> It's sensible, but not perfect. >> What I suggested is to add a generic layer: >> >> PCI-MSI -> >> A-MSI -> (generic layer) -> ITS -> GICR >> B-MSI -> >> >> The PCI/A/B/... passes its hardware properties to the generic layer which >> gets configurations ready by calling ITS's domain/chip callbacks. When >> a new device type arrives, the only thing need to do is to implement the >> driver of that device, with nothing to do with the generic layer or ITS. > > I really don't get your "generic layer" story. To me, it looks like a > glorified set of function pointers. And that's exactly what stacked > domains are giving you: > > A-MSI -> ITS -> GIC > > This "A-MSI" is responsible for: > - implementing the "prepare" callback, which allocates the ITT > - implementing the "irq_compose_msi_msg" > > Hardly anything to change in the ITS driver, and I can probably make it > so that you don't even have to write a single line of code in the ITS > driver. > > If the generic MSI layer we now have is not enough for you, then please > submit detailed use cases. >
Hi Marc, As I said, I never thought Gerry's patch don't work, I am just trying to make it better. :) As to the "generic layer" story, please check the following URL: https://lkml.org/lkml/2014/12/10/93 Thanks, Abel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
