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Date: Thu, 17 Jul 2014 13:01:22 +0100 From: Catalin Marinas <catalin.marinas@....com> To: Thierry Reding <thierry.reding@...il.com> Cc: Russell King <linux@....linux.org.uk>, Will Deacon <Will.Deacon@....com>, Arnd Bergmann <arnd@...db.de>, Stephen Boyd <sboyd@...eaurora.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v3 1/3] asm-generic/io.h: Implement generic {read,write}s*() On Wed, Jul 16, 2014 at 12:01:22PM +0100, Thierry Reding wrote: > From: Thierry Reding <treding@...dia.com> > > Currently driver writers need to use io{read,write}{8,16,32}_rep() when > accessing FIFO registers portably. This is bad for two reasons: it is > inconsistent with how other registers are accessed using the standard > {read,write}{b,w,l}() functions, which can lead to confusion. On some > architectures the io{read,write}*() functions also need to perform some > extra checks to determine whether an address is memory-mapped or refers > to I/O space. Drivers which can be expected to never use I/O can safely > use the {read,write}s{b,w,l,q}(), just like they use their non-string > variants and there's no need for these extra checks. > > This patch implements generic versions of readsb(), readsw(), readsl(), > readsq(), writesb(), writesw(), writesl() and writesq(). Variants of > these string functions for I/O accesses (ins*() and outs*() as well as > ioread*_rep() and iowrite*_rep()) are now implemented in terms of the > new functions. > > Going forward, {read,write}{,s}{b,w,l,q}() should be used consistently > by drivers for devices that will only ever be memory-mapped and hence > don't need to access I/O space, whereas io{read,write}{8,16,32}_rep() > should be used by drivers for devices that can be either memory-mapped > or I/O-mapped. > > While at it, also make sure that any of the functions provided as > fallback for architectures that don't override them can't be overridden > subsequently. > > This is compile- and runtime-tested on 32-bit and 64-bit ARM and compile > tested on Microblaze, s390, SPARC and Xtensa. For ARC, Blackfin, Metag, > OpenRISC, Score and Unicore32 which also use asm-generic/io.h I couldn't > find or build a cross-compiler that would run on my system. But by code > inspection they shouldn't break with this patch. > > Signed-off-by: Thierry Reding <treding@...dia.com> Acked-by: Catalin Marinas <catalin.marinas@....com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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