Re: [PATCH] platform-msi: Add ABI to show msi_irqs of platform devices

From: Barry Song
Date: Thu Aug 12 2021 - 05:14:16 EST


On Thu, Aug 12, 2021 at 7:24 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Aug 12, 2021 at 04:19:30PM +1200, Barry Song wrote:
> > > But why isn't this all handled by the MSI core code? Why would each bus
> > > need to have this logic in it?
> >
> > i think i can extract some common code for sysfs populate/destroy to msi core from pci and platform.
> > but we still need some pci/platform specific code in pci-msi and platform-msi cores. for example,
> > pci-msi has specific data which will be accessed in its show() entry.
> >
> > struct msi_desc {
> > ...
> > union {
> > /* PCI MSI/X specific data */
> > struct {
> > u32 masked;
> > struct {
> > u8 is_msix : 1;
> > u8 multiple : 3;
> > u8 multi_cap : 3;
> > u8 maskbit : 1;
> > u8 is_64 : 1;
> > u8 is_virtual : 1;
> > u16 entry_nr;
> > unsigned default_irq;
> > } msi_attrib;
> > union {
> > u8 mask_pos;
> > void __iomem *mask_base;
> > };
> > };
> >
> > ...
> > struct platform_msi_desc platform;
> > ...
> > };
> > };
> >
> > in addition, they are quite different in initialization/release and also need different places to save sysfs groups.
> > so probably i can let msi cores provide msi_populate_sysfs() and msi_destroy_sysfs() APIs. And ask pci and platform
> > to call msi_populate_sysfs() in their init code and save the groups in their specific pointers, and then they can
> > free sysfs in their release paths by calling msi_destroy_sysfs()
>
> Ok, if this isn't easy then I guess it's not a big deal, but you should
> go through the MSI developers first.
>
> Why does a platform device have MSI interrupts? I thought they were
> only for PCI devices.

I really don't know the story of hardware, but as long as a device can
write some mmio address with some
messages (interrupt-describing data) to generate interrupts instead of
using a hardware interrupt line, MSI is
supported :-)

>
> thanks,
>
> greg k-h

Thanks
Barry