linux-kernel - Re: [PATCHv3 00/14] drivers: mailbox: framework creation

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Date:	Wed, 24 Apr 2013 13:29:46 +0530
From:	Jassi Brar <jaswinder.singh@...aro.org>
To:	Loic PALLARDY <loic.pallardy@...com>
Cc:	"Anna, Suman" <s-anna@...com>,
	"Ohad Ben-Cohen (ohad@...ery.com)" <ohad@...ery.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Tony Lindgren <tony@...mide.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Andy Green (andy.green@...aro.org)" <andy.green@...aro.org>,
	"Omar Ramirez Luna (omar.ramirez@...itl.com)" 
	<omar.ramirez@...itl.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv3 00/14] drivers: mailbox: framework creation

Hi Loic,

On 24 April 2013 13:09, Loic PALLARDY <loic.pallardy@...com> wrote:
> Hi Jassi, Suman,
>
> Yes, the xxx_no_irq API has been introduced to answer some STE
> requirements. It must be possible to send some message under atomic
> context for different reasons (latency, during idle/suspend procedures...).
> This is not the best way to do, but the goal was to preserve TI legacy
> in a first step. As explained by Suman, this patch series is coming from
> the original TI mailbox framework and is modified step by step to fit
> with all platforms.
>
IMHO a better way is to introduce a clean generically designed API and
convert the existing drivers one at time. Let the TI drivers work as
such for a while until someone converts them to the common API.
Cloning and then complete organ transplantation seems a very
inefficient way to have something new ;)

>>>
>>> (d) The 'struct mailbox_msg' should be just an opaque void* - the client/protocol
>>> driver typecasts to void* the IPC controller specific message structure. API
>>> shouldn't aim the impossible of providing a generic message format.
>>
>> The size parameter would still be needed. Depending on the h/w, it can be just an u32 or a series of bytes, and even in the latter case, it is not guaranteed that all messages transmitted will occupy the entire h/w shared memory data packet. I can see the current header field getting absorbed into the opaque void * structure for the ST mailbox driver. The size and ptr together provide a very generic message format.
> That's something we discussed with Suman. The mailbox framework should
> be independent from message format. Since mailbox could be base don a
> shared mem or an hw fifo, message size is mandatory to transmit the
> right number of data.
>
I too believe the "mailbox framework should be independent from
message format" but _also_ that .size doesn't have to be a part of the
standard format.
Maybe it will help if I know what you guys mean by "shared mem" or an
"hw fifo" mailbox?

Thanks
-Jassi
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