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

From: Barry Song
Date: Thu Aug 12 2021 - 00:21:16 EST


>
> > +static ssize_t platform_msi_show(struct device *dev, struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct msi_desc *entry;
> > + unsigned long irq;
> > + int retval;
> > +
> > + retval = kstrtoul(attr->attr.name, 10, &irq);
> > + if (retval)
> > + return retval;
> > +
> > + entry = irq_get_msi_desc(irq);
> > + if (entry)
> > + return sprintf(buf, "msi\n");
>
> sysfs_emit()?

yep.

>
> 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()

>
> thanks,
>
> greg k-h

Thanks
Barry