From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: Re: [PATCH v3 1/3] asm-generic/io.h: Implement generic {read,write}s*() Date: Thu, 17 Jul 2014 13:01:22 +0100 Message-ID: <20140717120122.GG18203@arm.com> References: <1405508484-18303-1-git-send-email-thierry.reding@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from fw-tnat.austin.arm.com ([217.140.110.23]:19292 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754855AbaGQMBj (ORCPT ); Thu, 17 Jul 2014 08:01:39 -0400 Content-Disposition: inline In-Reply-To: <1405508484-18303-1-git-send-email-thierry.reding@gmail.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Thierry Reding Cc: Russell King , Will Deacon , Arnd Bergmann , Stephen Boyd , "linux-arm-kernel@lists.infradead.org" , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" On Wed, Jul 16, 2014 at 12:01:22PM +0100, Thierry Reding wrote: > From: Thierry Reding > > 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 Acked-by: Catalin Marinas