linux-kernel - Question about UIO vs DT

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Message-ID: <87o6vutrbw.wl-kuninori.morimoto.gx@renesas.com>
Date: Thu, 15 May 2025 04:45:23 +0000
From: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Linux-Kernel <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org,
	(Renesas)shimoda <yoshihiro.shimoda.uh@...esas.com>,
	(Renesas)goda <yusuke.goda.sx@...esas.com>,
	(Renesas)Kurokawa <harunobu.kurokawa.dn@...esas.com>,
	(Renesas)Kihara <takeshi.kihara.df@...esas.com>,
	kazuya.mizuguchi.ks@...esas.com, takamitsu.honda.pv@...esas.com
Subject: Question about UIO vs DT

Hi Greg / UIO / DT

I would like to ask about UIO vs DT.

If my understanding was correct, current UIO can use 1 IRQ / 1 reg per 1 UIO,
but some device needs multi-IRQ/reg. In such case, we need to use
multi-UIO. But it is not good much to DT rule. For example in case of
the device which needs "2 regs 3 irqs". it will be

(A)	[1 reg, 1 IRQ] UIO
(B)	[1 reg, 1 IRQ] UIO
(C)	[0 reg, 1 IRQ] UIO

and (C) will be DT error. Is this known issue ? Do we have better solution ?

Thank you for your help !!

Best regards
---
Kuninori Morimoto