linux-kernel - Re: [PATCH] platform-msi: Add ABI to show msi

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Message-ID: <YRTMuU4dE9RqyDC+@kroah.com>
Date:   Thu, 12 Aug 2021 09:24:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Barry Song <21cnbao@...il.com>
Cc:     linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        rafael@...nel.org, robin.murphy@....com,
        song.bao.hua@...ilicon.com, wangzhou1@...ilicon.com,
        will@...nel.org
Subject: Re: [PATCH] platform-msi: Add ABI to show msi_irqs of platform
 devices

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.

thanks,

greg k-h