From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Date: Wed, 04 May 2022 21:08:40 +0000 Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary Message-Id: <20220504210840.GA469916@bhelgaas> List-Id: In-Reply-To: <20220429135108.2781579-2-schnelle@linux.ibm.com> References: <20220429135108.2781579-2-schnelle@linux.ibm.com> In-Reply-To: <20220429135108.2781579-2-schnelle@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Niklas Schnelle Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pci@vger.kernel.org, Arnd Bergmann , Richard Henderson , Ivan Kokshaysky , Matt Turner , Russell King , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Michal Simek , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Paul Walmsley , Palmer Dabbelt , Albert Ou , Yoshinori Sato , Rich Felker , "David S. Miller" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:ALPHA PORT" , "moderated list:ARM PORT" , "open list:IA64 (Itanium) PLATFORM" , "open list:M68K ARCHITECTURE" , "open list:MIPS" , "open list:PARISC ARCHITECTURE" , "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" , "open list:RISC-V ARCHITECTURE" , "open list:SUPERH" , "open list:SPARC + UltraSPARC (sparc/sparc64)" On Fri, Apr 29, 2022 at 03:49:59PM +0200, Niklas Schnelle wrote: > We introduce a new HAS_IOPORT Kconfig option to indicate support for > I/O Port access. In a future patch HAS_IOPORT=n will disable compilation > of the I/O accessor functions inb()/outb() and friends on architectures > which can not meaningfully support legacy I/O spaces such as s390 or > where such support is optional. So you plan to drop inb()/outb() on architectures where I/O port space is optional? So even platforms that have I/O port space may not be able to use it? This feels like a lot of work where the main benefit is to keep Kconfig from offering drivers that aren't of interest on s390. Granted, there may be issues where inb()/outb() does the wrong thing such as dereferencing null pointers when I/O port space isn't implemented. I think that's a defect in inb()/outb() and could be fixed there. Bjorn