From mboxrd@z Thu Jan 1 00:00:00 1970 From: Santosh Shukla Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports Date: Tue, 29 Dec 2015 22:00:43 +0530 Message-ID: References: <20140509191914.GA7286@jtriplet-mobl1> <1961979.Xhiud0jvNd@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <1961979.Xhiud0jvNd@wuerfel> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann Cc: Santosh Shukla , Alex Williamson , "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 List-Id: linux-api@vger.kernel.org On Tue, Dec 29, 2015 at 9:50 PM, Arnd Bergmann wrote: > 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? > nothing wrong, infact read/write api will still be used so to access mmaped io pci bar at userspace. But right now vfio_pci_map() doesn't map io pci bar in particular (i.e.. ioresource_io) so I guess need to add that bar mapping in vfio. pl. correct me if i misunderstood anything. > Arnd