linux-kernel - Re: [PATCH v7 09/10] um: Add dummy implementation for IO memcpy/memset

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Message-ID: <168acf1cc03e2a7f4a918210ab2a05ee845ce247.camel@sipsolutions.net>
Date: Tue, 01 Oct 2024 14:53:31 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Julian Vetter <jvetter@...rayinc.com>, Arnd Bergmann <arnd@...db.de>, 
 Russell King <linux@...linux.org.uk>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>,  Guo Ren
 <guoren@...nel.org>, Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui
 <kernel@...0n.name>,  Andrew Morton <akpm@...ux-foundation.org>, Geert
 Uytterhoeven <geert@...ux-m68k.org>, Richard Henderson
 <richard.henderson@...aro.org>, Ivan Kokshaysky <ink@...assic.park.msu.ru>,
  Matt Turner <mattst88@...il.com>, "James E . J . Bottomley"
 <James.Bottomley@...senpartnership.com>,  Helge Deller <deller@....de>,
 Yoshinori Sato <ysato@...rs.sourceforge.jp>, Rich Felker <dalias@...c.org>,
 John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,  Richard
 Weinberger <richard@....at>, Anton Ivanov <anton.ivanov@...bridgegreys.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-csky@...r.kernel.org, loongarch@...ts.linux.dev, 
	linux-m68k@...ts.linux-m68k.org, linux-alpha@...r.kernel.org, 
	linux-parisc@...r.kernel.org, linux-sh@...r.kernel.org, 
	linux-um@...ts.infradead.org, linux-arch@...r.kernel.org, Yann Sionneau
	 <ysionneau@...rayinc.com>
Subject: Re: [PATCH v7 09/10] um: Add dummy implementation for IO
 memcpy/memset

On Mon, 2024-09-30 at 15:23 +0200, Julian Vetter wrote:
> The um arch is the only architecture that sets the config 'NO_IOMEM',
> yet drivers that use IO memory can be selected. In order to make these
> drivers happy we add a dummy implementation for memcpy_{from,to}io and
> memset_io functions.

Maybe I'm just not understanding this series, but how does this work
with lib/logic_iomem.c?

You're adding these inlines unconditionally, so if this included
logic_io.h, you should get symbol conflicts?

Also not sure these functions should/need to do anything at all, there's
no IO memory on ARCH=um in case of not having logic_io.h. Maybe even
BUG_ON() or something? It can't be reachable (under correct drivers)
since ioremap() always returns NULL (without logic_iomem).

I think Arnd also said that other architectures might want to use
logic_iomem, though I don't see any now.

johannes