Re: [PATCH 0/6] of: iommu-map parsing for multi-cell IOMMU

[Charan Teja Kalla]

On 11/7/2025 1:37 PM, Krzysztof Kozlowski wrote:
> On Tue, Nov 04, 2025 at 02:20:59PM +0530, Charan Teja Kalla wrote:
>> The iommu-map property has been defined for the PCIe usecase and has
>> been hardcoded to assume single cell for IOMMU specification, ignoring
>> the #iommu-cells completely. Since the initial definition the iommu-maps
>> property has been reused for other usecases and we can no longer assume
>> that the single IOMMU cell properly describes the necessary IOMMU
>> streams. Expand the iommu-map to take #iommu-cells into account, while
>> keeping the compatibility with the existing DTs, which assume single
>> argument. 
>>
>> Unlike single iommu-cell, it is complex to establish a linear relation
>> between input 'id' and output specifier for multi iommu-cells. To handle
>> such cases, rely on arch-specific drivers called through
>> of_iommu_xlate() from of_iommu layer, aswell it is expected the 'len'
>> passed is always 1. In the of_iommu layer, the below relation is
>> established before calling into vendor specific driver: 
>>
>> a) For platform devices, 'rid' defined in the iommu-map tuple indicates
>> a function, through a bit position, which is compared against passed
>> input 'id' that represents a bitmap of functions represented by the
>> device.
>>
>> b) For others, 'rid' is compared against the input 'id' as an integer
>> value.
>>
>> Thus the final representation when #iommu-cells=n is going to be,
>> iommu-map = <rid/functionid IOMMU_phandle cell0 .. celln len>;, where
>> len = 1.
>>
>> The RFC for this patch set is found at [2].
> So that's a v2 or v3? Then number your patchsets correctly.

Is there any kernel guidelines that patchset should start at V2 after an
RFC? I do see many patches are follwed by V1 after RFC. Eg: [1] is an
RFC followed by [2] as V1 -- Or it is the maintainers preference and
expectations?

> 
> Try yourself -  b4 diff cover.1762235099.git.charan.kalla@xxxxxxxxxxxxxxxx
> 
> Works? No.
> 
> Where is the changelog?My bad. Will update the changelog from RFC in my next patchset posting
as V2.


[1]
https://lore.kernel.org/all/20250815191031.3769540-1-Liam.Howlett@xxxxxxxxxx/
[2]
https://lore.kernel.org/all/20250909190945.1030905-1-Liam.Howlett@xxxxxxxxxx/#t