linux-kernel - Re: [PATCHv5 2/4] mailbox: Introduce framework for mailbox

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Date:	Thu, 15 May 2014 16:27:20 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
	s-anna@...com, loic.pallardy@...com, lftan.linux@...il.com,
	slapdau@...oo.com.au, courtney.cavin@...ymobile.com,
	robherring2@...il.com, joshc@...eaurora.org,
	linus.walleij@...aro.org, galak@...eaurora.org,
	ks.giri@...sung.com, Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCHv5 2/4] mailbox: Introduce framework for mailbox

On Thursday 15 May 2014 11:41:00 Jassi Brar wrote:
> Introduce common framework for client/protocol drivers and
> controller drivers of Inter-Processor-Communication (IPC).
> 
> Client driver developers should have a look at
>  include/linux/mailbox_client.h to understand the part of
> the API exposed to client drivers.
> Similarly controller driver developers should have a look
> at include/linux/mailbox_controller.h
> 
> Signed-off-by: Jassi Brar <jaswinder.singh@...aro.org>

I hadn't followed all the previous versions, but this looks very nice!

I only have comments about tiny details.

> new file mode 100644
> index 0000000..0eb2fb0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/mailbox.txt
> @@ -0,0 +1,30 @@
> +* Generic Mailbox Controller and client driver bindings
> +
> +Generic binding to provide a way for Mailbox controller drivers to assign appropriate mailbox channel to client drivers.
> +
> +* MAILBOX Controller

Just formatting: wrap the lines after 70 characters, and don't use
capital letters for 'mailbox'.
> +
> +enum mbox_result {
> +	MBOX_OK = 0,
> +	MBOX_ERR,
> +};

How about using a standard error number?

> +/**
> + * struct mbox_client - User of a mailbox
> + * @dev:		The client device
> + * @chan_name:		The "controller:channel" this client wants
> + * @rx_callback:	Atomic callback to provide client the data received
> + * @tx_done:		Atomic callback to tell client of data transmission
> + * @tx_block:		If the mbox_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.
> + */
> +struct mbox_client {
> +	struct device *dev;
> +	const char *chan_name;
> +	void (*rx_callback)(struct mbox_client *cl, void *mssg);
> +	void (*tx_done)(struct mbox_client *cl, void *mssg, enum mbox_result r);
> +	bool tx_block;
> +	unsigned long tx_tout;
> +	bool knows_txdone;
> +};
> +
> +struct mbox_chan *mbox_request_channel(struct mbox_client *cl);

Is it possible to make the argument 'const'?

Maybe document how you expect an mbox_client to be allocated:
- static const definition in driver
- dynamically allocated and embedded in some client specific struct
- on the stack and discarded after mbox_request_channel()

> +/**
> + * struct mbox_controller - Controller of a class of communication chans
> + * @dev:		Device backing this controller
> + * @controller_name:	Literal name of the controller.
> + * @ops:		Operators that work on each communication chan
> + * @chans:		Null terminated array of chans.
> + * @txdone_irq:		Indicates if the controller can report to API when
> + *			the last transmitted data was read by the remote.
> + *			Eg, if it has some TX ACK irq.
> + * @txdone_poll:	If the controller can read but not report the TX
> + *			done. Ex, some register shows the TX status but
> + *			no interrupt rises. Ignored if 'txdone_irq' is set.
> + * @txpoll_period:	If 'txdone_poll' is in effect, the API polls for
> + *			last TX's status after these many millisecs
> + */
> +struct mbox_controller {
> +	struct device *dev;
> +	struct mbox_chan_ops *ops;
> +	struct mbox_chan *chans;
> +	int num_chans;
> +	bool txdone_irq;
> +	bool txdone_poll;
> +	unsigned txpoll_period;
> +	struct mbox_chan *(*of_xlate)(struct mbox_controller *mbox,
> +					const struct of_phandle_args *sp);
> +	/*
> +	 * If the controller supports only TXDONE_BY_POLL,
> +	 * this timer polls all the links for txdone.
> +	 */
> +	struct timer_list poll;
> +	unsigned period;
> +	/* Hook to add to the global controller list */
> +	struct list_head node;
> +} __aligned(32);

What is the __aligned(32) for?

	Arnd
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