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SubjectRe: [PATCH 2/6] fpga: manager: don't use drvdata in common fpga code
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.

Alan

>
> thanks,
>
> greg k-h

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