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SubjectRe: [PATCH 02/16] fpga: add FPGA device framework
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?

thanks,

greg k-h

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