Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932327AbdCaGJg (ORCPT ); Fri, 31 Mar 2017 02:09:36 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:52766 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751012AbdCaGJY (ORCPT ); Fri, 31 Mar 2017 02:09:24 -0400 X-ME-Sender: X-Sasl-enc: djkao30Ur/6xqU00+gyUxFHKt7p+qrGhrT2caqB+OsNJ 1490940562 Date: Fri, 31 Mar 2017 08:09:09 +0200 From: Greg KH To: Wu Hao Cc: atull@kernel.org, moritz.fischer@ettus.com, linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, luwei.kang@intel.com, yi.z.zhang@intel.com, Tim Whisonant , Enno Luebbers , Shiva Rao , Christopher Rauer , Xiao Guangrong Subject: Re: [PATCH 02/16] fpga: add FPGA device framework Message-ID: <20170331060909.GA7621@kroah.com> References: <1490875696-15145-1-git-send-email-hao.wu@intel.com> <1490875696-15145-3-git-send-email-hao.wu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1490875696-15145-3-git-send-email-hao.wu@intel.com> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2124 Lines: 61 On Thu, Mar 30, 2017 at 08:08:02PM +0800, Wu Hao wrote: > During FPGA device (e.g PCI-based) discovery, platform devices are > registered for different FPGA function units. But the device node path > isn't quite friendly to applications. > > Consider this case, applications want to access child device's sysfs file > for some information. > > 1) Access using bus-based path (e.g PCI) > > /sys/bus/pci/devices/xxxxx/fpga_func_a.0/sysfs_file > > From the path, it's clear which PCI device is the parent, but not perfect > solution for applications. PCI device BDF is not fixed, application may > need to search all PCI device to find the actual FPGA Device. > > 2) Or access using platform device path > > /sys/bus/platform/devices/fpga_func_a.0/sysfs_file > > Applications find the actual function by name easily, but no information > about which fpga device it belongs to. It's quite confusing if multiple > FPGA devices are in one system. > > 'FPGA Device' class is introduced to resolve this problem. Each node under > this class represents a fpga device, which may have one or more child > devices. Applications only need to search under this FPGA Device class > folder to find the child device node it needs. > > For example, for the platform has 2 fpga devices, each fpga device has > 3 child devices, the hierarchy looks like this. > > Two nodes are under /sys/class/fpga/: > /sys/class/fpga/fpga.0 > /sys/class/fpga/fpga.1 > > Each node has 1 function A device and 2 function B devices: > /sys/class/fpga/fpga.0/func_a.0 > /sys/class/fpga/fpga.0/func_b.0 > /sys/class/fpga/fpga.0/func_b.1 > > /sys/class/fpga/fpga.1/func_a.1 > /sys/class/fpga/fpga.1/func_b.2 > /sys/class/fpga/fpga.1/func_b.3 > > This following APIs are provided by FPGA device framework: > * fpga_dev_create > Create fpga device under the given parent device. > * fpga_dev_destroy > Destroy fpga device > > The following sysfs files are created: > * /sys/class/fpga//name > Name of the fpga device. How does this interact with the existing "fpga class" that is in the kernel already? thanks, greg k-h