netdev - Re: [PATCH net-next 2/5] net: rpmsg-eth: Add basic rpmsg skeleton

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Message-ID: <4bb1339a-ead6-4a33-b2bf-c55874bab352@ti.com>
Date: Wed, 30 Jul 2025 11:31:03 +0530
From: MD Danish Anwar <danishanwar@...com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>,
        Jonathan Corbet <corbet@....net>, Andrew Lunn
	<andrew+netdev@...n.ch>,
        Mengyuan Lou <mengyuanlou@...-swift.com>,
        Michael
 Ellerman <mpe@...erman.id.au>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Fan
 Gong <gongfan1@...wei.com>, Lee Trager <lee@...ger.us>,
        Lorenzo Bianconi
	<lorenzo@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Lukas
 Bulwahn <lukas.bulwahn@...hat.com>,
        Parthiban Veerasooran
	<Parthiban.Veerasooran@...rochip.com>
CC: <netdev@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/5] net: rpmsg-eth: Add basic rpmsg skeleton



On 29/07/25 6:02 pm, Krzysztof Kozlowski wrote:
> On 29/07/2025 11:46, MD Danish Anwar wrote:
>>>>
>>>> One idea I had was to create a new binding for this node, and use
>>>> compatible string to access the node in driver. But the device is
>>>> virtual and not physical so I thought that might not be the way to go so
>>>> I went with the current approach.
>>>
>>> virtual devices do not go to DTS anyway. How do you imagine this works?
>>> You add it to DTS but you do not add bindings and you expect checks to
>>> succeed?
>>>
>>> Provide details how you checked your DTS compliance.
>>>
>>>
>>
>> This is my device tree patch [1]. I ran these two commands before and
>> after applying the patch and checked the diff.
>>
>> 	make dt_binding_check
>> 	make dtbs_check
>>
>> I didn't see any new error / warning getting introduced due to the patch
>>
>> After applying the patch I also ran,
>>
>> 	make CHECK_DTBS=y ti/k3-am642-evm.dtb
>>
>> I still don't see any warnings / error.
>>
>>
>> If you look at the DT patch, you'll see I am adding a new node in the
> 
> I see. This is so odd syntax... You have the phandle there, so you do
> not need to do any node name checking. I did not really expect you will
> be checking node name for reserved memory!!!
> 

I don't have access to the phandle in my function. The reserved memory
is reserved by ti_k3_r5_remoteproc driver. That driver has the phandle.

I am writing a new driver rpmsg_eth, this driver only has the rpdev
structure. This driver doesn't have any dt node or phandle and because
of this I am doing `peer = of_find_node_by_name(NULL,
"virtual-eth-shm");` to get the access to this node here.

I couldn't find any way to access the dt node of reserved memory from
this (rpmsg_eth) driver. Please let me know if there is any way I can
access that.

> Obviously this will be fine with dt bindings, because such ABI should
> never be constructed.
> 
> 
>> `reserved-memory`. I am not creating a completely new undocumented node.
>> Instead I am creating a new node under reserved-memory as the shared
>> memory used by rpmsg-eth driver needs to be reserved first. This memory
>> is reserved by the ti_k3_r5_remoteproc driver by k3_reserved_mem_init().
>>
>> It's just that I am naming this node as "virtual-eth-shm@...00000" and
>> then using the same name in driver to get the base_address and size
>> mentioned in this node.
> 
> And how your driver will work with:
> 
> s/virtual-eth-shm@...00000/whatever@...00000/
> 


It won't. The driver imposes a restriction with the node name. The node
name should always be "virtual-eth-shm"

For other vendors who want to use this driver, they need to reserve
memory for their shared block and name the node `virtual-eth-shm@...XXXXX`

> ? It will not.
> 
> Best regards,
> Krzysztof

-- 
Thanks and Regards,
Danish