From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports Date: Tue, 29 Dec 2015 17:20:08 +0100 Message-ID: <1961979.Xhiud0jvNd@wuerfel> References: <20140509191914.GA7286@jtriplet-mobl1> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Santosh Shukla Cc: alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, "H. Peter Anvin" , josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org, Greg Kroah-Hartman , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Linux Kernel Mailing List , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, yuanhan.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, Santosh Shukla List-Id: linux-api@vger.kernel.org On Tuesday 29 December 2015 21:25:15 Santosh Shukla wrote: > mistakenly added wrong email-id of alex, looping his correct one. > > On 29 December 2015 at 21:23, Santosh Shukla wrote: > > On 29 December 2015 at 18:58, Arnd Bergmann wrote: > >> On Wednesday 23 December 2015 17:04:40 Santosh Shukla wrote: > >>> On 23 December 2015 at 03:26, Arnd Bergmann wrote: > >>> > On Tuesday 22 December 2015, Santosh Shukla wrote: > >>> >> } > >>> >> > >>> >> So I care for /dev/ioport types interface who could do more than byte > >>> >> data copy to/from user-space. I tested this patch with little > >>> >> modification and could able to run pmd driver for arm/arm64 case. > >>> >> > >>> >> Like to know how to address pci_io region mapping problem for > >>> >> arm/arm64, in-case /dev/ioports approach is not acceptable or else I > >>> >> can spent time on restructuring the patch? > >>> >> > >>> > > >>> > For the use case you describe, can't you use the vfio framework to > >>> > access the PCI BARs? > >>> > > >>> > >>> I looked at file: drivers/vfio/pci/vfio_pci.c, func vfio_pci_map() and > >>> it look to me that it only maps ioresource_mem pci region, pasting > >>> code snap: > >>> > >>> if (!(pci_resource_flags(pdev, index) & IORESOURCE_MEM)) > >>> return -EINVAL; > >>> .... > >>> > >>> and I want to map ioresource_io pci region for arm platform in my > >>> use-case. Not sure vfio maps pci_iobar region? > >> > >> Mapping I/O BARs is not portable, notably it doesn't work on x86. > >> > >> You should be able access them using the read/write interface on > >> the vfio device. > >> > > Right, x86 doesn't care as iopl() could give userspace application > > direct access to ioports. > > > > Also, Alex in other dpdk thread [1] suggested someone to propose io > > bar mapping in vfio-pci, I guess in particular to non-x86 arch so I > > started working on it. > > > So what's wrong with just using the existing read/write API on all architectures? Arnd