Message-ID: <CANk1AXSKQ1A66sTn3KMNN3G6bXm7aifp5yr90-bgWyTYSb=9ww@mail.gmail.com>
Date:   Mon, 13 Nov 2017 11:51:59 -0600
From:   Alan Tull <atull@...nel.org>
To:     Moritz Fischer <mdf@...nel.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org
Subject: Re: [PATCH 2/3] fpga: manager: don't use drvdata in common fpga code

On Tue, Oct 31, 2017 at 9:22 PM, Alan Tull <atull@...nel.org> wrote:

Any further comments on v5?  I'm getting ready to send v6.  If I do it
today, most of these patches will have no changes (again), the only
changes will be in the patches that move drvdata out of the common
code.

I've gone to a lot of trouble to break out functional patches to make
them easy to review and to keep what I was trying to accomplish clear
here.  I think this stuff is necessary going forward.  If this stuff
doesn't have errors, let's move forward and make whatever changes we
want to make on top of this.

Alan

> On Tue, Oct 31, 2017 at 8:34 PM, Moritz Fischer <mdf@...nel.org> wrote:
>> On Tue, Oct 31, 2017 at 04:45:54PM -0500, Alan Tull wrote:
>>> On Tue, Oct 31, 2017 at 3:59 PM, Moritz Fischer <mdf@...nel.org> wrote:
>>> > On Tue, Oct 31, 2017 at 08:42:14PM +0000, Alan Tull wrote:
>>> >> Changes to the fpga manager code to not use drvdata in common
>>> >> code.
>>> >>
>>> >> Change fpga_mgr_register to not set or use drvdata.
>>> >>
>>> >> Change the register/unregister function parameters to take the mgr
>>> >> struct:
>>> >> * int fpga_mgr_register(struct device *dev,
>>> >>                         struct fpga_manager *mgr);
>>> >> * void fpga_mgr_unregister(struct fpga_manager *mgr);
>>> >>
>>> >> Change the drivers that call fpga_mgr_register to alloc the struct
>>> >> fpga_manager (using devm_kzalloc) and partly fill it, adding name,
>>> >> ops, and priv.
>>> >>
>>> >> The rationale is that setting drvdata is fine for DT based devices
>>> >> that will have one manager, bridge, or region per platform device.
>>> >> However PCIe based devices may have multiple FPGA mgr/bridge/regions
>>> >> under one pcie device.  Without these changes, the PCIe solution has
>>> >> to create an extra device for each child mgr/bridge/region to hold
>>> >> drvdata.
>>> >
>>> > This looks very common, in fact several subsystems provide this two step
>>> > way of registering things.
>>> >
>>> > - Allocate fpga_mgr via fpga_mgr_alloc() where you pass in the size of
>>> >   the private data
>>> > - Fill in some fields
>>> > - fpga_mgr_register() where you pass in the fpga_mgr as suggested
>>> >
>>> > See for example the alloc_etherdev() for ethernet devices.
>>> >
>>>
>>> Yes, I considered it when I was writing this.  I've seen it both ways.
>>> In the case you mention, they've got reasons they absolutely needed to
>>> do it that way.  alloc_etherdev() calls eventually to
>>> alloc_netdev_mqs() which is about 100 lines of alloc'ing and
>>> initializing a network device struct.
>>
>> Yeah, sure. I looked around some more. Other subsystems just alloc
>> manually, seems fine with me.
>>>
>>> > The benefit of the API you proposed is that one could embed the fpga_mgr
>>> > struct inside of another struct and get to the container via
>>> > container_of() I guess ...
>>>
>>> Yes, let's keep it simple for now, as that gives us greater
>>> flexibility.  We can add alloc functions when it becomes clear that it
>>> won't get in the way of someone's use.
>>
>> Agreed.
>>>
>>> Alan
>>>
>>> >
>>> >>
>>> >> Signed-off-by: Alan Tull <atull@...nel.org>
>>> >> Reported-by: Jiuyue Ma <majiuyue@...wei.com>
>>> >> ---
>>> >>  Documentation/fpga/fpga-mgr.txt  | 23 ++++++++++++++++-------
>>> >>  drivers/fpga/altera-cvp.c        | 17 +++++++++++++----
>>> >>  drivers/fpga/altera-pr-ip-core.c | 16 ++++++++++++++--
>>> >>  drivers/fpga/altera-ps-spi.c     | 17 ++++++++++++++---
>>> >>  drivers/fpga/fpga-mgr.c          | 28 +++++++---------------------
>>> >>  drivers/fpga/ice40-spi.c         | 19 +++++++++++++++----
>>> >>  drivers/fpga/socfpga-a10.c       | 15 ++++++++++++---
>>> >>  drivers/fpga/socfpga.c           | 17 ++++++++++++++---
>>> >>  drivers/fpga/ts73xx-fpga.c       | 17 ++++++++++++++---
>>> >>  drivers/fpga/xilinx-spi.c        | 17 ++++++++++++++---
>>> >>  drivers/fpga/zynq-fpga.c         | 15 ++++++++++++---
>>> >>  include/linux/fpga/fpga-mgr.h    |  6 ++----
>>> >>  12 files changed, 147 insertions(+), 60 deletions(-)
>>> >>
>>> >> diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
>>> >> index cc6413e..7e5e5c8 100644
>>> >> --- a/Documentation/fpga/fpga-mgr.txt
>>> >> +++ b/Documentation/fpga/fpga-mgr.txt
>>> >> @@ -67,11 +67,9 @@ fpga_mgr_unlock when done programming the FPGA.
>>> >>  To register or unregister the low level FPGA-specific driver:
>>> >>  -------------------------------------------------------------
>>> >>
>>> >> -     int fpga_mgr_register(struct device *dev, const char *name,
>>> >> -                           const struct fpga_manager_ops *mops,
>>> >> -                           void *priv);
>>> >> +     int fpga_mgr_register(struct device *dev, struct fpga_manager *mgr);
>>
>> At that point you could also just give the struct fpga_manager a
>> ->parent or ->dev that you populate with &pdev->dev or &spi->dev etc instead of
>> making it a separate parameter, this makes an odd mix of half and half here.
>
> Yes, I'd have to call it parent as dev is taken.  I also noticed that
> I forgot to edit the function parameter documentation in the c file.
>
>>> >>
>>> >> -     void fpga_mgr_unregister(struct device *dev);
>>> >> +     void fpga_mgr_unregister(struct fpga_manager *mgr);
>>> >>
>>> >>  Use of these two functions is described below in "How To Support a new FPGA
>>> >>  device."
>>> >> @@ -148,8 +146,13 @@ static int socfpga_fpga_probe(struct platform_device *pdev)
>>> >>  {
>>> >>       struct device *dev = &pdev->dev;
>>> >>       struct socfpga_fpga_priv *priv;
>>> >> +     struct fpga_manager *mgr;
>>> >>       int ret;
>>> >>
>>> >> +     mgr = devm_kzalloc(dev, sizeof(*mgr), GFP_KERNEL);
>>> >> +     if (!mgr)
>>> >> +             return -ENOMEM;
>>> >> +
>>> >>       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>> >>       if (!priv)
>>> >>               return -ENOMEM;
>>> >> @@ -157,13 +160,19 @@ static int socfpga_fpga_probe(struct platform_device *pdev)
>>> >>       /* ... do ioremaps, get interrupts, etc. and save
>>> >>          them in priv... */
>>> >>
>>> >> -     return fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager",
>>> >> -                              &socfpga_fpga_ops, priv);
>>> >> +     mgr->name = "Altera SOCFPGA FPGA Manager";
>>> >> +     mgr->mops = &socfpga_fpga_ops;
>>> >> +     mgr->priv = priv;
>> Like here: mgr->dev = &pdev->dev
>
> Yes, good catch.  By the way, I pushed these patches on a branch to
> linux-fpga (branch name is review-v4.14-rc7-non-dt-support-v5.1).
>
> Thanks for reviewing,
> Alan
>
>>
>>> >> +     platform_set_drvdata(pdev, mgr);
>>> >> +
>>> >> +     return fpga_mgr_register(dev, mgr);
>>> >>  }

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