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

[MD Danish Anwar <danishanwar@ti.com>]

Hi Krzysztof,

On 25/07/25 12:48 am, Krzysztof Kozlowski wrote:
> On 23/07/2025 10:03, MD Danish Anwar wrote:
>> This patch introduces a basic RPMSG Ethernet driver skeleton. It adds
> 
> Please do not use "This commit/patch/change", but imperative mood. See
> longer explanation here:
> https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95
> 

Sure. I will fix this in v2.

>> support for creating virtual Ethernet devices over RPMSG channels,
>> allowing user-space programs to send and receive messages using a
>> standard Ethernet protocol. The driver includes message handling,
>> probe, and remove functions, along with necessary data structures.
>>
> 
> 
> ...
> 
>> +
>> +/**
>> + * rpmsg_eth_get_shm_info - Get shared memory info from device tree
>> + * @common: Pointer to rpmsg_eth_common structure
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +static int rpmsg_eth_get_shm_info(struct rpmsg_eth_common *common)
>> +{
>> +	struct device_node *peer;
>> +	const __be32 *reg;
>> +	u64 start_address;
>> +	int prop_size;
>> +	int reg_len;
>> +	u64 size;
>> +
>> +	peer = of_find_node_by_name(NULL, "virtual-eth-shm");
> 
> 
> This is new ABI and I do not see earlier patch documenting it.
> 
> You cannot add undocumented ABI... but even if you documented it, I am
> sorry, but I am pretty sure it is wrong. Why are you choosing random
> nodes just because their name by pure coincidence is "virtual-eth-shm"?
> I cannot name my ethernet like that?
> 

This series adds a new virtual ethernet driver. The tx / rx happens in a
shared memory block. I need to have a way for the driver to know what is
the address / size of this block. This driver can be used by any
vendors. The vendors can create a new node in their dt and specify the
base address / size of the shared memory block.

I wanted to keep the name of the node constant so that the driver can
just look for this name and then grab the address and size.

I can create a new binding file for this but I didn't create thinking
it's a virtual device not a physical and I wasn't sure if bindings can
be created for virtual devices.

In my use case, I am reserving this shared memory and during reserving I
named the node "virtual-eth-shm". The memory is reserved by the
ti_k3_r5_remoteproc.c driver. The DT change is not part of this series
but can be found
https://gist.github.com/danish-ti/cdd10525ad834fdb20871ab411ff94fb

The idea is any vendor who want to use this driver, should name their dt
node as "virtual-eth-shm" (if they also need to reserve the memory) so
that the driver can take the address from DT and use it for tx / rx.

If this is not the correct way, can you please let me know of some other
way to handle this.

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.

> Best regards,
> Krzysztof

-- 
Thanks and Regards,
Danish