Re: [PATCH net-next] net: airoha: Add missing filed to ppe_mbox_data struct

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> On 4/16/25 5:55 PM, Lorenzo Bianconi wrote:
> >> On Tue, Apr 15, 2025 at 09:27:21AM +0200, Lorenzo Bianconi wrote:
> >>> The official Airoha EN7581 firmware requires adding max_packet filed in
> >>> ppe_mbox_data struct while the unofficial one used to develop the Airoha
> >>> EN7581 flowtable offload does not require this field. This patch fixes
> >>> just a theoretical bug since the Airoha EN7581 firmware is not posted to
> >>> linux-firware or other repositories (e.g. OpenWrt) yet.
> >>>
> >>> Fixes: 23290c7bc190d ("net: airoha: Introduce Airoha NPU support")
> >>> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> >>> ---
> >>>  drivers/net/ethernet/airoha/airoha_npu.c | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/drivers/net/ethernet/airoha/airoha_npu.c b/drivers/net/ethernet/airoha/airoha_npu.c
> >>> index 7a5710f9ccf6a4a4f555ab63d67cb6b318de9b52..16201b5ce9f27866896226c3611b4a154d19bc2c 100644
> >>> --- a/drivers/net/ethernet/airoha/airoha_npu.c
> >>> +++ b/drivers/net/ethernet/airoha/airoha_npu.c
> >>> @@ -104,6 +104,7 @@ struct ppe_mbox_data {
> >>>  			u8 xpon_hal_api;
> >>>  			u8 wan_xsi;
> >>>  			u8 ct_joyme4;
> >>> +			u8 max_packet;
> >>>  			int ppe_type;
> >>>  			int wan_mode;
> >>>  			int wan_sel;
> >>
> >> Hi Lorenzo,
> >>
> >> I'm a little confused by this.
> >>
> >> As I understand it ppe_mbox_data is sent as the data of a mailbox message
> >> send to the device.  But by adding the max_packet field the layout is
> >> changed. The size of the structure changes. And perhaps more importantly
> >> the offset of fields after max_packet, e.g.  wan_mode, change.
> >>
> >> Looking at how this is used, f.e. in the following code, I'm unclear on
> >> how this change is backwards compatible.
> > 
> > you are right Simon, this change is not backwards compatible but the fw is
> > not publicly available yet and the official fw version will use this new layout
> > (the previous one was just a private version I used to develop the driver).
> > Can we use this simple approach or do you think we should differentiate the two
> > firmware version in some way? (even if the previous one will never be used).
> 
> I think it's better if you clarify the commit message. I read the above
> as the current (unpatched) code will not work with the official
> firmware, so bug addressed here does not look theoretical.

ack, I will fix it in v2.

Regards,
Lorenzo

> 
> Thanks,
> 
> Paolo
> 

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