linux-kernel - Re: [PATCH] smc91x: remove ARM hack for unaligned 16-bit writes

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Date:   Fri, 26 Aug 2016 11:56:16 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Nicolas Pitre <nico@...xnic.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] smc91x: remove ARM hack for unaligned 16-bit writes

On Friday, August 26, 2016 11:41:21 AM CEST Arnd Bergmann wrote:
> 
> I think this breaks machines that declare a device that just lists
> SMC91X_USE_32BIT but not SMC91X_USE_16BIT. Right now, the way this
> is interpreted is to use 32-bit accessors for most things, but
> not avoiding 16-bit reads.

I guess my patch has the same problem here, with the

	if (SMC_CAN_USE_8BIT && !SMC_16BIT(lp))

check that is true when a platform device is declared with 32-bit
I/O only but all three are enabled at compile-time. The best check
I can think of here (aside from redefining how the flags work)
would be

#define SMC_8BIT_ONLY(p) 	\
	(((p)->cfg.flags & (SMC91X_USE_8BIT |SMC91X_USE_16BIT | SMC91X_USE_32BIT)) == \
	 SMC91X_USE_8BIT)


	Arnd