linux-kernel - Using the mailbox subsystem for plain doorbells?

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Message-ID: <5731210A.4000401@wwwdotorg.org>
Date:	Mon, 9 May 2016 17:45:14 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Joseph Lo <josephl@...dia.com>
Subject: Using the mailbox subsystem for plain doorbells?

Jassi,

Does the HW described below sound like something that should be 
represented using the Linux kernel's mailbox subsystem, and related DT 
bindings? I think the existing drivers/mailbox/pcc.c is similar, but 
wanted to double-check.

We have some HW that literally just allows a SW-generated interrupt to 
be generated by our main CPU complex to an auxiliary CPU, and likewise a 
different interrupt can be generated in the opposite direction. There's 
no ability to transfer any data; just an IRQ is generated. Our current 
mailbox implementation just handles IRQ generation/reception so struct 
mbox_chan_ops.send_data completely ignores the data parameter, and our 
IRQ handler "receives" hard-coded NULL messages when the IRQ fires. 
Higher level protocol code (using shared memory along with the plain-IRQ 
mbox channels) is outside the mailbox driver.

Does that fit the mailbox subsystem?