Re: [PATCH RFC v2 2/4] iommu/arm-smmu-v3: Support shared SIDs in insert/remove_master

[Nicolin Chen <nicolinc@nvidia.com>]

On Tue, Sep 22, 2026 at 04:52:35PM +0100, Robin Murphy wrote:
> On 22/09/2026 3:13 pm, Peng Fan wrote:
> > On Mon, Sep 21, 2026 at 04:15:18PM -0700, Nicolin Chen wrote:
> > > Does i.MX need to support SID-sharing with multi-SD device? If not,
> > > the master could have only a simple shared_masters_elm:
> > 
> > For i.MX, there is no need to support SID sharing for multi-SID device for now.
> > Not sure, in future there are cases that needs SID sharing for multi-SID device.
> 
> I have a system meeting those conditions :)
> 
> Specifically, I have a physical PCIe-to-PCI bridge board with a couple of
> ancient cards plugged into it (such that they each end up with their own RID
> plus the common bridge alias RID) just in case I ever got round to looking
> at this myself...

Though in such cases we cannot reject num_streams != 1 any more,
that bridge can still end up with one single shared stream, e.g.
 alias  = PCI_DEVID(0x02, PCI_DEVFN(0,0)) = 0x0200
 Card A = 02:01.0 -> sorted SIDs { 0x0200, 0x0208 }
 Card B = 02:02.0 -> sorted SIDs { 0x0200, 0x0210 }
?

Hopefully, we won't have to support an ancient PCIe-to-PCI bridge
connecting with another ancient PCI-to-PCI bridge...

Nicolin