From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Arnd Bergmann" Date: Wed, 10 May 2023 15:54:18 +0000 Subject: Re: [PATCH v6 5/6] fbdev: Move framebuffer I/O helpers into Message-Id: <743d2b1e-c843-4fb2-b252-0006be2e2bd8@app.fastmail.com> List-Id: References: <20230510110557.14343-6-tzimmermann@suse.de> <202305102136.eMjTSPwH-lkp@intel.com> <49684d58-c19d-b147-5e9f-2ac526dd50f0@suse.de> In-Reply-To: <49684d58-c19d-b147-5e9f-2ac526dd50f0@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Thomas Zimmermann , kernel test robot , Helge Deller , Geert Uytterhoeven , Javier Martinez Canillas , Daniel Vetter , Vineet Gupta , Huacai Chen , WANG Xuerui , "David S . Miller" , "James E . J . Bottomley" , Sam Ravnborg , suijingfeng@loongson.cn Cc: oe-kbuild-all@lists.linux.dev, Linux-Arch , linux-fbdev@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-m68k@lists.linux-m68k.org, loongarch@lists.linux.dev, sparclinux@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org On Wed, May 10, 2023, at 16:27, Thomas Zimmermann wrote: > Am 10.05.23 um 16:15 schrieb Arnd Bergmann: >> On Wed, May 10, 2023, at 16:03, kernel test robot wrote: >> I think that's a preexisting bug and I have no idea what the >> correct solution is. Looking for HD64461 shows it being used >> both with inw/outw and readw/writew, so there is no way to have >> the correct type. The sh __raw_readw() definition hides this bug, >> but that is a problem with arch/sh and it probably hides others >> as well. > > The constant HD64461_IOBASE is defined as integer at > > > https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/hd64461.h#L17 > > but fb_readw() expects a volatile-void pointer. I guess we could add a > cast somewhere to silence the problem. In the current upstream code, > that appears to be done by sh's __raw_readw() internally: > > > https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/io.h#L35 Sure, that would make it build again, but that still doesn't make the code correct, since it's completely unclear what base address the HD64461_IOBASE is relative to. The hp6xx platform code only passes it through inw()/outw(), which take an offset relative to sh_io_port_base, but that is not initialized on hp6xx. I tried to find in the history when it broke, apparently that was in 2007 commit 34a780a0afeb ("sh: hp6xx pata_platform support."), which removed the custom inw/outw implementations. Arnd