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Date: Thu, 9 May 2024 22:36:57 +0200
From: Andrew Lunn <andrew@lunn.ch>
To: Thorsten Blum <thorsten.blum@toblux.com>
Cc: Nicolas Pitre <nico@fluxnic.net>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Arnd Bergmann <arnd@arndb.de>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: smc91x: Fix m68k kernel compilation for ColdFire CPU
Message-ID: <98259c2f-b44a-467e-8854-48641984e468@lunn.ch>
References: <20240509121713.190076-2-thorsten.blum@toblux.com>
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In-Reply-To: <20240509121713.190076-2-thorsten.blum@toblux.com>

On Thu, May 09, 2024 at 02:17:14PM +0200, Thorsten Blum wrote:
> Compiling the m68k kernel with support for the ColdFire CPU family fails
> with the following error:
> 
> In file included from drivers/net/ethernet/smsc/smc91x.c:80:
> drivers/net/ethernet/smsc/smc91x.c: In function ‘smc_reset’:
> drivers/net/ethernet/smsc/smc91x.h:160:40: error: implicit declaration of function ‘_swapw’; did you mean ‘swap’? [-Werror=implicit-function-declaration]
>   160 | #define SMC_outw(lp, v, a, r)   writew(_swapw(v), (a) + (r))
>       |                                        ^~~~~~
> drivers/net/ethernet/smsc/smc91x.h:904:25: note: in expansion of macro ‘SMC_outw’
>   904 |                         SMC_outw(lp, x, ioaddr, BANK_SELECT);           \
>       |                         ^~~~~~~~
> drivers/net/ethernet/smsc/smc91x.c:250:9: note: in expansion of macro ‘SMC_SELECT_BANK’
>   250 |         SMC_SELECT_BANK(lp, 2);
>       |         ^~~~~~~~~~~~~~~
> cc1: some warnings being treated as errors
> 
> The function _swapw() was removed in commit d97cf70af097 ("m68k: use
> asm-generic/io.h for non-MMU io access functions"), but is still used in
> drivers/net/ethernet/smsc/smc91x.h.
> 
> Re-adding the previously deleted _swapw() function resolves the error.

This seems like the wrong fix.

commit d97cf70af09721ef416c61faa44543e3b84c9a55
Author: Greg Ungerer <gerg@linux-m68k.org>
Date:   Fri Mar 23 23:39:10 2018 +1000

    m68k: use asm-generic/io.h for non-MMU io access functions
    
    There is nothing really special about the non-MMU m68k IO access functions.
    So we can easily switch to using the asm-generic/io.h functions.

So it rather than put something back which there is an aim to remove,
please find the generic replacement. This _swapw() swaps a 16 bit
word. The generic for that is swab16().

I'm also surprised it took 6 years to find this. Has something else
changed recently?

    Andrew

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