linux-kernel - Re: [PATCHv2 2/4] mailbox: Introduce a new common API

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Date:	Thu, 9 May 2013 11:40:55 -0500
From:	Suman Anna <s-anna@...com>
To:	Jassi Brar <jaswinder.singh@...aro.org>
CC:	Jassi Brar <jassisinghbrar@...il.com>,
	"Loic PALLARDY (loic.pallardy@...com)" <loic.pallardy@...com>,
	Arnd Bergmann <arnd@...db.de>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv2 2/4] mailbox: Introduce a new common API

On 05/09/2013 11:41 AM, Jassi Brar wrote:
> On 9 May 2013 22:01, Suman Anna <s-anna@...com> wrote:
>> Hi Jassi,
>>
>> On 05/06/2013 02:24 AM, Jassi Brar wrote:
>>> +++ b/include/linux/mailbox_client.h
>>> @@ -0,0 +1,85 @@
>>> +/*
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#ifndef __MAILBOX_CLIENT_H
>>> +#define __MAILBOX_CLIENT_H
>>> +
>>> +#include <linux/mailbox.h>
>>> +
>>> +/**
>>> + * struct ipc_client - User of a mailbox
>>> + * @chan_name: the "controller:channel" this client wants
>>> + * @rxcb: atomic callback to provide client the data received
>>> + * @txcb: atomic callback to tell client of data transmission
>>> + * @tx_block: if the ipc_send_message should block until data is transmitted
>>> + * @tx_tout: Max block period in ms before TX is assumed failure
>>> + * @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.
>>> + * @cntlr_data: Optional controller specific parameters during channel request
>>> + */
>>> +struct ipc_client {
>>> +     char *chan_name;
>>> +     void (*rxcb)(void *data);
>>> +     void (*txcb)(request_token_t t, enum xfer_result r);
>>
>> We have to introduce a callback data pointer, so that the calling
>> clients can retrieve a context object variable or some other useful
>> data within the callback functions, just like most normal callback
>> function declarations and registrations do.
>>
> I meant the request_token_t for the purpose. That's how we do with DMAEngine.

I faced this issue on the rxcb while adopting the
omap_rproc_mbox_callback. omap_remoteproc is a common driver for all the
OMAP co-processors and there can be multiple instances, providing the
same set of features. Look at the code in
drivers/remoteproc/omap_remoteproc.c and you will get the idea. But in
general, the users registering callback functions would prefer to get
some context pointer back.

regards
Suman

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