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SubjectRe: [RFC V2 PATCH 2/3] dt-bindings: net: xilinx_axienet: Introduce dmaengine binding support
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On 21/09/2022 10:23, Pandey, Radhey Shyam wrote:
>>> required:
>>> - compatible
>>> - interrupts
>>> - reg
>>> - xlnx,rxmem
>>> - phy-handle
>>> + - dmas
>>> + - dma-names
>>>
>>> additionalProperties: false
>>>
>>> @@ -132,11 +137,13 @@ examples:
>>> axi_ethernet_eth: ethernet@40c00000 {
>>> compatible = "xlnx,axi-ethernet-1.00.a";
>>> interrupt-parent = <&microblaze_0_axi_intc>;
>>> - interrupts = <2>, <0>, <1>;
>>> + interrupts = <1>;
>>
>> This looks like an ABI break. How do you handle old DTS? Oh wait... you do
>> not handle it at all.
>
> Yes, this is anticipated ABI break due to major changes in axiethernet
> driver while adopting to dmaengine framework. Same is highlighted
> in commit description - "DT changes are not backward compatible
> due to major driver restructuring/cleanup done in adopting the
> dmaengine framework".
>
> Some background - Factor out AXI DMA code into separate driver was
> a TODO item (mentioned in driver changelog) and is being done as
> part of this series. The DMA code is removed from axiethernet driver
> and ethernet driver now make use of dmaengine framework to
> communicate with AXIDMA IP.
>
> When DMA code is removed from axiethernet driver there is limitation
> to support legacy DMA resources binding. One option is to inform
> user to switch to new binding when old DTS is detected? (and at some
> point we have to make this transition and remove dma code).

If you keep ABI non-broken, such message is a good idea.

> Please let us know if there are any other alternative to consider?

You just cannot break ABI just because you want to refactor some code in
driver.


Best regards,
Krzysztof

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