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SubjectRe: [PATCH 2/6] fpga: manager: don't use drvdata in common fpga code
On Thu, Mar 29, 2018 at 01:26:39PM -0500, Alan Tull wrote:
> On Thu, Mar 29, 2018 at 12:03 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> Hi Greg,
>
> > On Thu, Mar 29, 2018 at 08:36:54AM -0700, Moritz Fischer wrote:
> >> From: Alan Tull <atull@kernel.org>
> >>
> >> 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 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, parent device, 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.
> >>
> >> Signed-off-by: Alan Tull <atull@kernel.org>
> >> Reported-by: Jiuyue Ma <majiuyue@huawei.com>
> >> Signed-off-by: Moritz Fischer <mdf@kernel.org>
> >> ---
> >> Documentation/fpga/fpga-mgr.txt | 24 +++++++++++++++++-------
> >> drivers/fpga/altera-cvp.c | 18 ++++++++++++++----
> >> drivers/fpga/altera-pr-ip-core.c | 17 +++++++++++++++--
> >> drivers/fpga/altera-ps-spi.c | 18 +++++++++++++++---
> >> drivers/fpga/fpga-mgr.c | 39 ++++++++++++++-------------------------
> >> drivers/fpga/ice40-spi.c | 20 ++++++++++++++++----
> >> drivers/fpga/socfpga-a10.c | 16 +++++++++++++---
> >> drivers/fpga/socfpga.c | 18 +++++++++++++++---
> >> drivers/fpga/ts73xx-fpga.c | 18 +++++++++++++++---
> >> drivers/fpga/xilinx-spi.c | 18 +++++++++++++++---
> >> drivers/fpga/zynq-fpga.c | 16 +++++++++++++---
> >> include/linux/fpga/fpga-mgr.h | 8 ++++----
> >> 12 files changed, 166 insertions(+), 64 deletions(-)
> >>
> >> diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
> >> index cc6413ed6fc9..3cea6b57c156 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 fpga_manager *mgr);
> >>
> >> - 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;
> >
> > This feels odd to have to do for every driver. Why can't the fpga core
> > handle this all for you?
> >
> >
> >> +
> >> priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >> if (!priv)
> >> return -ENOMEM;
> >> @@ -157,13 +160,20 @@ 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);
> >
> > Why can't this be:
> > fpga_mgr_create(...)
> > that returns the correct structure? That way each driver always gets
> > the proper things set (you don't have to remember and audit each driver
> > to ensure they do it all correctly), and all is good?
> >
> > That should make this a lot simpler to use, and change.
>
> Are you suggesting something like this?
>
> - return fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager",
> - &socfpga_fpga_ops, priv);
> + mgr = fpga_mgr_create(dev, "Altera SOCFPGA FPGA Manager",
> + &socfpga_fpga_ops, priv);
> +
> + platform_set_drvdata(pdev, mgr);
> +
> + return fpga_mgr_register(mgr);
>
> That would be straightforward and if there are more fields to fill in
> in the future, we can still do that before calling fpga_mgr_register.

Or you can add another parameter to the fpga_mgr_create() call :)

Yes, that looks a lot better, thanks.

greg k-h

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