On Fri, Mar 31, 2017 at 12:01:13PM -0700, matthew.gerl...@linux.intel.com wrote: > On Fri, 31 Mar 2017, Wu Hao wrote: > >On Fri, Mar 31, 2017 at 08:09:09AM +0200, Greg KH wrote: > >>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/<fpga.x>/name > >>> Name of the fpga device. > >> > >>How does this interact with the existing "fpga class" that is in the > >>kernel already? > > > >The fpga-dev introduced by this patch, is only a container device, and > > I completely understand the need for a container device. The fpga-region is > also primarily a container, and in some cases the fpga-region may represent > the entire fpga. Over time this code may become redundant.
Thanks a lot for your review and comments. I feel that the fpga-region implies that it supports reconfiguration, but in our cases, the Intel FPGA device, doesn't have base fpga-region for full reconfiguration, but many accelerators with partial reconfiguration support. A fpga-region brings together everything needed for the reconfiguration, and a fpga-dev is trying to brings everything on a FPGA device together, including fpga-region/bridge/manager, access different accelerators and other function units. I think it's not mandatory to use fpga-dev, as fpga-dev is just trying to provide one more option here for some complex hardware. Thanks Hao > >drivers could register different functions under it. Per my understanding, > >the existing "fpga class", including fpga-region, fpga-bridge and > >fpga-manager, is used to provide reconfiguration function for FPGA. So > >driver can create child node using this existing "fpga class" to provide > >FPGA reconfiguration function, and more nodes under this container for > >different functions for given FPGA device. > > > >For Intel FPGA device, partial reconfiguration is only one function of > >Intel FPGA Management Engine (FME). FME driver creates fpga_manager under > >below path for partial reconfiguration, and other interfaces for more > >functions, e.g power management, virtualization support and etc. > > > >/sys/class/fpga/<fpga.x>/<intel-fpga-fme.x>/fpga_manager > > > >Thanks > >Hao > > > >> > >>thanks, > >> > >>greg k-h > >-- > >To unsubscribe from this list: send the line "unsubscribe linux-fpga" in > >the body of a message to majord...@vger.kernel.org > >More majordomo info at http://vger.kernel.org/majordomo-info.html > >