netdev - Re: [PATCH net-next v29 1/3] mailbox: add callback function for rx buffer allocation

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Message-ID: <aNafiYk3_Ma5QQ4Q@horms.kernel.org>
Date: Fri, 26 Sep 2025 15:13:29 +0100
From: Simon Horman <horms@...nel.org>
To: Adam Young <admiyo@...amperecomputing.com>
Cc: Jassi Brar <jassisinghbrar@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jeremy Kerr <jk@...econstruct.com.au>,
	Matt Johnston <matt@...econstruct.com.au>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH net-next v29 1/3] mailbox: add callback function for rx
 buffer allocation

On Thu, Sep 25, 2025 at 03:00:24PM -0400, Adam Young wrote:
> Allows the mailbox client to specify how to allocate the memory
> that the mailbox controller uses to send the message to the client.
> 
> In the case of a network driver, the message should be allocated as
> a struct sk_buff allocated and managed by the network subsystem.  The
> two parameters passed back from the callback represent the sk_buff
> itself and the data section inside the skbuff where the message gets
> written.
> 
> For simpler cases where the client kmallocs a buffer or returns
> static memory, both pointers should point to the same value.
> 
> Signed-off-by: Adam Young <admiyo@...amperecomputing.com>
> ---
>  include/linux/mailbox_client.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/include/linux/mailbox_client.h b/include/linux/mailbox_client.h
> index c6eea9afb943..901184d0515e 100644
> --- a/include/linux/mailbox_client.h
> +++ b/include/linux/mailbox_client.h
> @@ -21,6 +21,12 @@ struct mbox_chan;
>   * @knows_txdone:	If the client could run the TX state machine. Usually
>   *			if the client receives some ACK packet for transmission.
>   *			Unused if the controller already has TX_Done/RTR IRQ.
> + * @rx_alloc		Optional callback that allows the driver

@rx_alloc:
        ^^^

Flagged by ./scripts/kernel-doc -none -Wall

> + *			to allocate the memory used for receiving
> + *			messages.  The handle parameter is the value to return
> + *			to the client,buffer is the location the mailbox should
> + *			write to, and size it the size of the buffer to allocate.
> + *			inside the buffer where the mailbox should write the data.
>   * @rx_callback:	Atomic callback to provide client the data received
>   * @tx_prepare: 	Atomic callback to ask client to prepare the payload
>   *			before initiating the transmission if required.
> @@ -32,6 +38,7 @@ struct mbox_client {
>  	unsigned long tx_tout;
>  	bool knows_txdone;
>  
> +	void (*rx_alloc)(struct mbox_client *cl, void **handle, void **buffer, int size);
>  	void (*rx_callback)(struct mbox_client *cl, void *mssg);
>  	void (*tx_prepare)(struct mbox_client *cl, void *mssg);
>  	void (*tx_done)(struct mbox_client *cl, void *mssg, int r);
> -- 
> 2.43.0
> 
>