From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753495AbdC0PTR (ORCPT ); Mon, 27 Mar 2017 11:19:17 -0400 Received: from smtp5-g21.free.fr ([212.27.42.5]:37756 "EHLO smtp5-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752775AbdC0PTK (ORCPT ); Mon, 27 Mar 2017 11:19:10 -0400 Subject: Re: [RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge To: Thomas Gleixner Cc: Marc Zyngier , Bjorn Helgaas , Robin Murphy , Lorenzo Pieralisi , Liviu Dudau , David Laight , linux-pci , Linux ARM , Thibaud Cornic , Phuong Nguyen , LKML References: <91db1f47-3024-9712-309a-fb4b21e42028@free.fr> <310db9dd-7db6-2106-2e53-f0083b2d3758@free.fr> <9fffedd4-6292-b662-a588-a68fe7380af6@free.fr> <6e847686-43c6-11e9-6782-dec0fe81a58e@arm.com> <9c65e647-8395-4467-53ca-c20ed374131b@free.fr> From: Mason Message-ID: <4f426de0-b24a-c8dc-76a0-d4ec607a86be@free.fr> Date: Mon, 27 Mar 2017 17:18:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:51.0) Gecko/20100101 Firefox/51.0 SeaMonkey/2.48 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/03/2017 16:46, Thomas Gleixner wrote: > On Mon, 27 Mar 2017, Mason wrote: > >> On 24/03/2017 19:22, Marc Zyngier wrote: >> >>> You cannot directly use a pointer to a u32 in any of the bitmap >>> operations. You need to copy the value to an unsigned long, and >>> apply the bitmap op on that. >> >> On my platform, find_first_zero_bit() resolves to >> >> int _find_first_zero_bit_le(const void * p, unsigned size); >> >> If the underlying implementation actually expects an unsigned long >> pointer, should the function prototype be changed? > > Errm? Why are you worrying about the underlying implementations? > > find_first_zero_bit() is what you are supposed to use in your code. And > that explicitely takes a unsigned long pointer. I don't think so. If the prototype for find_first_zero_bit() specified the first argument as an unsigned long pointer, then the compiler would have rejected my code like this: CC drivers/pci/host/pcie-tango.o In file included from ./include/linux/bitops.h:36:0, from ./include/linux/kernel.h:10, from ./include/linux/list.h:8, from ./include/linux/smp.h:11, from ./include/linux/irq.h:12, from ./include/linux/irqchip/chained_irq.h:21, from drivers/pci/host/pcie-tango.c:1: drivers/pci/host/pcie-tango.c: In function 'tango_irq_domain_alloc': drivers/pci/host/pcie-tango.c:122:28: error: passing argument 1 of '_find_first_zero_bit_le' from incompatible pointer type [-Werror=incompatible-pointer-types] pos = find_first_zero_bit(&mask, 32); ^ ./arch/arm/include/asm/bitops.h:199:59: note: in definition of macro 'find_first_zero_bit' #define find_first_zero_bit(p,sz) _find_first_zero_bit_le(p,sz) ^ ./arch/arm/include/asm/bitops.h:162:12: note: expected 'const long unsigned int *' but argument is of type 'u32 * {aka unsigned int *}' extern int _find_first_zero_bit_le(const unsigned long * p, unsigned size); ^ cc1: some warnings being treated as errors make[1]: *** [drivers/pci/host/pcie-tango.o] Error 1 make: *** [drivers/pci/host/pcie-tango.o] Error 2 But, in fact, the compiler remained silent, specifically because the situation on my platform is: #define find_first_zero_bit(p,sz) _find_first_zero_bit_le(p,sz) int _find_first_zero_bit_le(const void * p, unsigned size); So I asked if the prototype could/should be changed, to have the compiler catch the error as early as possible. Regards.