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From: Wu Hao <hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: Alan Tull <atull-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Moritz Fischer <mdf-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-fpga-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"Kang,
	Luwei" <luwei.kang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	"Zhang,
	Yi Z" <yi.z.zhang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Tim Whisonant
	<tim.whisonant-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Enno Luebbers
	<enno.luebbers-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Shiva Rao <shiva.rao-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Christopher Rauer
	<christopher.rauer-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH v2 02/22] fpga: add FPGA device framework
Date: Tue, 1 Aug 2017 16:43:26 +0800	[thread overview]
Message-ID: <20170801084326.GB26227@hao-dev> (raw)
In-Reply-To: <CANk1AXTsBQgX+0hYZA6mMhESApB-MkG9CETWExSPOpf7MXeKFw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Mon, Jul 31, 2017 at 04:40:16PM -0500, Alan Tull wrote:
> On Thu, Jul 27, 2017 at 2:10 PM, Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> > On Thu, Jul 27, 2017 at 11:35 AM, Alan Tull <atull-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> >> On Sun, Jun 25, 2017 at 8:51 PM, Wu Hao <hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
> >>
> >> Hi Rob,
> >>
> >> I was hoping to pick your brain a bit on a DT question.
> >>
> >>> 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.
> >>
> >> There's a proposal for adding sysfs nodes that correspond to each FPGA
> >> device., with the devices located on each FPGA under them.  It makes
> >> it easier to see which device is on which FPGA.
> >
> > Makes sense.
> >
> >>> '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
> >
> > A class is generally what is the function of the device, not how it is
> > attached. Seems like what you want here is a new bus type if the
> > existing PCI and platform bus types don't work.
> >
> >>
> >> I can see the value of having sysfs nodes that correspond to fpga
> >> devices and being able to find devices under them.  I'm thinking what
> >> that would mean for Device Tree when fpga-dev is used on DT enabled
> >> systems.  In Device Tree, what is a fpga-dev?
> >
> > Just properly setting the parent struct device on the functions should
> > be enough to figure out which function is in which fpga. I don't see
> > why a new class is needed.
> >
> >> Currently the DT would have a FPGA bridge corresponding to each FPGA's
> >> hardware bridge and a heirarchy of bridges, regions and devices under
> >> it.  On systems that don't support partial reconfiguration under the
> >> OS (so not main bridge that was controlled by the OS), there would be
> >> a FPGA region, then its child regions, bridges, and devices.
> >
> > The FPGA bridges could instantiate fpga bus type devices instead of
> > platform devices.
> 
> Yes
> 
> Some FPGA use cases already have a base bridge per FPGA that could
> serve as this bus.  But this use case has a static FPGA image +
> reprogrammable child fpga regions.  There's no base bridge under Linux
> since the FPGA was programmed and the bridge enabled before Linux
> boots.   An added base bridge that doesn't touch hardware will be
> required for this type of use.

Hi Alan

Does 'base bridge' mentioned above mean a hardware bridge just like
PCIe or USB?

I tried to use fpga bus type device instead of fpga-dev class today,
it works for me, e.g Intel FPGA device PCIe driver could create a
fpga bus type dev as a child of PCIe device and its sysfs path will be
changed to /sys/bus/fpga/devices/fpga.x/ from /sys/class/fpga/fpga.x/.
For now, this fpga bus type device is only used as container device,
so no driver needed for it.

Do you have any concern on this? I see fpga bus type works fine, but
I didn't see other advantages for this case, as we only use it as a
container device to represent a FPGA device in sysfs hierarchy. :)

Thanks
Hao

> 
> > That's really up to Linux and outside the scope of
> > the bindings.
> 
> Thanks for the feedback.
> 
> Alan Tull
> 
> >
> > Rob

  parent reply	other threads:[~2017-08-01  8:43 UTC|newest]

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-26  1:51 [PATCH v2 00/22] Intel FPGA Device Drivers Wu Hao
     [not found] ` <1498441938-14046-1-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-06-26  1:51   ` [PATCH v2 01/22] docs: fpga: add a document for Intel FPGA driver overview Wu Hao
2017-07-12 14:51     ` Alan Tull
     [not found]       ` <CANk1AXTDVVRG05H9kwZujFYGGS=AjQ2cdfrBm=bRNz9S7p6R6w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-13  4:25         ` Wu Hao
2017-07-14 23:59           ` Luebbers, Enno
2017-07-17 20:14             ` Alan Tull
     [not found]               ` <CANk1AXTLhbczboA=wCYGUhnJyyYfvmUqUpk490sk34eh-MU5Ew-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-18  5:22                 ` Greg KH
     [not found]                   ` <20170718052228.GA10631-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-07-18 14:32                     ` Alan Tull
2017-06-26  1:51   ` [PATCH v2 02/22] fpga: add FPGA device framework Wu Hao
2017-07-27 16:35     ` Alan Tull
     [not found]       ` <CANk1AXRoxz7nOY--UYfBtg-3kGFy0gqCz0cbF9mOvzU2+EdzpA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-27 19:10         ` Rob Herring
     [not found]           ` <CAL_JsqJfGJwDcXtpBs73TsSKTCwfAPywgyTPwzy1GQotJ7DTzw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-31 21:40             ` Alan Tull
     [not found]               ` <CANk1AXTsBQgX+0hYZA6mMhESApB-MkG9CETWExSPOpf7MXeKFw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-01  8:43                 ` Wu Hao [this message]
2017-08-01 21:04                   ` Alan Tull
2017-08-02 14:07                     ` Wu Hao
2017-08-02 21:01                       ` Alan Tull
2017-08-07 15:13             ` Alan Tull
2017-07-27 16:44     ` Alan Tull
     [not found]       ` <CANk1AXR-nSB-6TKpVyskbvfj_F2=jbSv48hpp+UXtKxkTseLqw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-28  7:55         ` Wu Hao
2017-06-26  1:51   ` [PATCH v2 03/22] fpga: bridge: remove OF dependency for fpga-bridge Wu Hao
2017-08-02 21:21     ` Alan Tull
2017-09-25 16:34       ` Moritz Fischer
     [not found]     ` <1498441938-14046-4-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-09-21 19:11       ` Moritz Fischer
2017-09-21 19:50         ` Alan Tull
     [not found]           ` <CANk1AXRbXybjwq-ha=G6Z7nXwd8fNjPWP5awTz6=23KVXbd=kQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-09-22  2:15             ` Wu Hao
2017-09-23  1:53               ` Alan Tull
2017-06-26  1:52   ` [PATCH v2 04/22] fpga: mgr: add region_id to fpga_image_info Wu Hao
     [not found]     ` <1498441938-14046-5-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-07-26 18:33       ` Alan Tull
2017-07-27  5:14         ` Wu Hao
2017-06-26  1:52   ` [PATCH v2 09/22] fpga: intel: pcie: adds fpga_for_each_port callback for fme device Wu Hao
2017-08-17 21:31     ` Alan Tull
     [not found]       ` <CANk1AXRQfGViXn+vEErmN6N8LtOsX7Arh-VPPbDjKiEyGGvV-A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-18  7:03         ` Wu Hao
2017-06-26  1:52   ` [PATCH v2 10/22] fpga: intel: add feature device infrastructure Wu Hao
2017-06-26  1:52   ` [PATCH v2 12/22] fpga: intel: fme: add header sub feature support Wu Hao
2017-07-17 18:53     ` Alan Tull
2017-07-18  1:17       ` Wu, Hao
     [not found]         ` <BE8371DA886269458E0220A16DC1F8277E058300-0J0gbvR4kTg/UvCtAeCM4rfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2017-07-18 14:33           ` Alan Tull
2017-06-26  1:52   ` [PATCH v2 14/22] fpga: intel: fme: add partial reconfiguration " Wu Hao
2017-06-26  1:52   ` [PATCH v2 16/22] fpga: intel: add fpga bridge platform driver for FME Wu Hao
     [not found]     ` <1498441938-14046-17-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-17 19:34       ` Alan Tull
2017-08-17 19:55     ` Moritz Fischer
2017-08-18  3:06       ` Wu Hao
2017-06-26  1:52   ` [PATCH v2 18/22] fpga: intel: add FPGA Accelerated Function Unit driver basic framework Wu Hao
     [not found]     ` <1498441938-14046-19-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-17 19:00       ` Alan Tull
     [not found]         ` <CANk1AXSN76qZD+h8iBeYGPEGwquvGms9VC2tXG7rf16NeNUoiw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-18  6:40           ` Wu Hao
2017-08-17 19:09     ` Moritz Fischer
     [not found]       ` <CAAtXAHca6R7rKOmFHD0eic1dv-NxfG3fBS+yRVFNYoX_M0eVbw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-18  6:42         ` Wu Hao
2017-06-26  1:52   ` [PATCH v2 19/22] fpga: intel: afu: add header sub feature support Wu Hao
2017-08-14 21:37     ` Alan Tull
     [not found]       ` <CANk1AXSb==KikMjw4PJ4Yx97vT5JxDkHR5k2Cb0cdrQFUOZqQw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-16  5:11         ` Wu, Hao
2017-08-17 21:41           ` Alan Tull
2017-06-26  1:52   ` [PATCH v2 20/22] fpga: intel: afu add FPGA_GET_API_VERSION/CHECK_EXTENSION ioctls support Wu Hao
2017-08-17 19:07     ` Alan Tull
2017-08-17 19:12     ` Moritz Fischer
     [not found]       ` <CAAtXAHdyCNBRHdk-9L+AOT7g7BEsxBN-EkdhxO2-aSqdDovTHg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-18  3:20         ` Wu Hao
2017-06-26  1:52   ` [PATCH v2 21/22] fpga: intel: afu: add user afu sub feature support Wu Hao
2017-06-26  1:52   ` [PATCH v2 22/22] fpga: intel: afu: add FPGA_PORT_DMA_MAP/UNMAP ioctls support Wu Hao
2017-07-31 21:41     ` Alan Tull
     [not found]       ` <CANk1AXQ0kKnDOWo_BLA_r3P_rsmiZ1LQCVWqXtmXYmkUnzDtog-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-01  7:21         ` Wu Hao
2017-08-01 18:15     ` Moritz Fischer
     [not found]       ` <CAAtXAHfB906JNRzwzrx9kB4kMwcTz-201QQSr=486j8hrH7WMA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-02  7:30         ` Wu Hao
2017-07-28 13:28   ` [PATCH v2 00/22] Intel FPGA Device Drivers Alan Tull
2017-06-26  1:52 ` [PATCH v2 05/22] fpga: mgr: add status for fpga-mgr Wu Hao
     [not found]   ` <1498441938-14046-6-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-07-12 15:22     ` Alan Tull
     [not found]       ` <CANk1AXQ4-BWzhRjR+BTmnSae+4FeBamZyYbH1MMZWaAqeW_CEA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-13  3:11         ` Wu Hao
2017-06-26  1:52 ` [PATCH v2 06/22] fpga: intel: add FPGA PCIe device driver Wu Hao
2017-08-07 20:43   ` Alan Tull
     [not found]     ` <CANk1AXQ__fFCfv335ySGMxG=8UXReEk8V1=a-3pCw5S-v=sSRQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-14 12:33       ` Wu, Hao
2017-06-26  1:52 ` [PATCH v2 07/22] fpga: intel: pcie: parse feature list and create platform device for features Wu Hao
2017-06-26 18:42   ` Moritz Fischer
2017-06-27  3:17     ` Wu Hao
     [not found]     ` <20170626184205.GA13190-R0KNJUYl863z/wjs7L+eiWPmTBeX6bocVpNB7YpNyf8@public.gmane.org>
2017-06-27 15:34       ` Alan Tull
     [not found]   ` <1498441938-14046-8-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-07-13 17:52     ` Alan Tull
     [not found]       ` <CANk1AXS-VftzKmmK4P3Anas+DQZ0ZPQ=7yVQt=QrNULPY7PaDA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-14  9:22         ` Wu Hao
2017-07-17 19:15   ` Alan Tull
2017-07-18  2:29     ` Wu, Hao
2017-09-20 21:24   ` Alan Tull
2017-09-21 19:58     ` Alan Tull
     [not found]       ` <CANk1AXTvHm-y0vUmCTPX47T9G1TJsatfwoC-bx-tPFRoJA9+AA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-09-22  7:33         ` Wu Hao
2017-09-22  7:28     ` Wu Hao
2017-09-27 20:27       ` Alan Tull
     [not found]         ` <CANk1AXQe2mrpqq-7uc8QvPPBYaMvQjBhbjLaee1XQ6L+kiCKTQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-09-28  9:32           ` Wu Hao
2017-06-26  1:52 ` [PATCH v2 08/22] fpga: intel: pcie: add chardev support for feature devices Wu Hao
2017-06-26  1:52 ` [PATCH v2 11/22] fpga: intel: add FPGA Management Engine driver basic framework Wu Hao
2017-06-26  1:52 ` [PATCH v2 13/22] fpga: intel: fme: add FPGA_GET_API_VERSION/CHECK_EXTENSION ioctls support Wu Hao
2017-08-17 19:11   ` Alan Tull
2017-06-26  1:52 ` [PATCH v2 15/22] fpga: intel: add fpga manager platform driver for FME Wu Hao
2017-09-25 21:24   ` Moritz Fischer
     [not found]     ` <20170925212457.GB14795-KFgJe6S/L2nknyRNNOXSQ2IaLvZF3x2V0E9HWUfgJXw@public.gmane.org>
2017-09-27  1:18       ` Wu Hao
2017-09-27 18:54         ` Alan Tull
     [not found]           ` <CANk1AXTQLiR7ayLzsgU9TOePY2Zc01P-mMOy7n509S7+bcS-5A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-09-28  8:25             ` Wu Hao
2017-06-26  1:52 ` [PATCH v2 17/22] fpga: intel: add fpga region " Wu Hao
     [not found]   ` <1498441938-14046-18-git-send-email-hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-07-12 16:09     ` Alan Tull
     [not found]       ` <CANk1AXRioZsobi9k_VVcRypV+LrviPLjRejb_Og9VwKhCRth5g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-07-13  2:31         ` Wu Hao

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