Message-ID: <CANk1AXSFGBO3Jrv2VrQmQhSV0sBdsrq1mUn-HARQGoxNTwtsjg@mail.gmail.com>
Date:   Tue, 19 Sep 2017 10:35:12 -0500
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 v4 01/18] fpga: bridge: support getting bridge from device

On Mon, Sep 18, 2017 at 5:53 PM, Moritz Fischer <mdf@...nel.org> wrote:

Hi Moritz,

> On Wed, Sep 13, 2017 at 03:48:24PM -0500, Alan Tull wrote:
>> Add two functions for getting the FPGA bridge from the device
>> rather than device tree node.  This is to enable writing code
>> that will support using FPGA bridges without device tree.
>> Rename one old function to make it clear that it is device
>> tree-ish.  This leaves us with 3 functions for getting a bridge:
>>
>> * fpga_bridge_get
>>   Get the bridge given the device.
>>
>> * fpga_bridges_get_to_list
>>   Given the device, get the bridge and add it to a list.
>>
>> * of_fpga_bridges_get_to_list
>>   Renamed from priviously existing fpga_bridges_get_to_list.
>>   Given the device node, get the bridge and add it to a list.
>>
>> Signed-off-by: Alan Tull <atull@...nel.org>
>> ---
>> v2: use list_for_each_entry
>>     static the bridge_list_lock
>>     update copyright and author email
>> v3: no change to this patch in this version of patchset
>> v4: no change to this patch in this version of patchset
>> ---
>>  drivers/fpga/fpga-bridge.c       | 110 +++++++++++++++++++++++++++++++--------
>>  drivers/fpga/fpga-region.c       |  11 ++--
>>  include/linux/fpga/fpga-bridge.h |   7 ++-
>>  3 files changed, 100 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
>> index fcd2bd3..af6d97e 100644
>> --- a/drivers/fpga/fpga-bridge.c
>> +++ b/drivers/fpga/fpga-bridge.c
>> @@ -2,6 +2,7 @@
>>   * FPGA Bridge Framework Driver
>>   *
>>   *  Copyright (C) 2013-2016 Altera Corporation, All Rights Reserved.
>> + *  Copyright (C) 2017 Intel Corporation
>>   *
>>   * This program is free software; you can redistribute it and/or modify it
>>   * under the terms and conditions of the GNU General Public License,
>> @@ -70,29 +71,12 @@ int fpga_bridge_disable(struct fpga_bridge *bridge)
>>  }
>>  EXPORT_SYMBOL_GPL(fpga_bridge_disable);
>>
>> -/**
>> - * of_fpga_bridge_get - get an exclusive reference to a fpga bridge
>> - *
>> - * @np: node pointer of a FPGA bridge
>> - * @info: fpga image specific information
>> - *
>> - * Return fpga_bridge struct if successful.
>> - * Return -EBUSY if someone already has a reference to the bridge.
>> - * Return -ENODEV if @np is not a FPGA Bridge.
>> - */
>> -struct fpga_bridge *of_fpga_bridge_get(struct device_node *np,
>> -                                    struct fpga_image_info *info)
>> -
>> +struct fpga_bridge *__fpga_bridge_get(struct device *dev,
>> +                                   struct fpga_image_info *info)
>>  {
>> -     struct device *dev;
>>       struct fpga_bridge *bridge;
>>       int ret = -ENODEV;
>>
>> -     dev = class_find_device(fpga_bridge_class, NULL, np,
>> -                             fpga_bridge_of_node_match);
>> -     if (!dev)
>> -             goto err_dev;
>> -
>>       bridge = to_fpga_bridge(dev);
>>       if (!bridge)
>>               goto err_dev;
>> @@ -117,8 +101,58 @@ struct fpga_bridge *of_fpga_bridge_get(struct device_node *np,
>>       put_device(dev);
>>       return ERR_PTR(ret);
>>  }
>> +
>> +/**
>> + * of_fpga_bridge_get - get an exclusive reference to a fpga bridge
>> + *
>> + * @np: node pointer of a FPGA bridge
>> + * @info: fpga image specific information
>> + *
>> + * Return fpga_bridge struct if successful.
>> + * Return -EBUSY if someone already has a reference to the bridge.
>> + * Return -ENODEV if @np is not a FPGA Bridge.
>> + */
>> +struct fpga_bridge *of_fpga_bridge_get(struct device_node *np,
>> +                                    struct fpga_image_info *info)
>> +{
>> +     struct device *dev;
>> +
>> +     dev = class_find_device(fpga_bridge_class, NULL, np,
>> +                             fpga_bridge_of_node_match);
>> +     if (!dev)
>> +             return ERR_PTR(-ENODEV);
>> +
>> +     return __fpga_bridge_get(dev, info);
>> +}
>>  EXPORT_SYMBOL_GPL(of_fpga_bridge_get);
>>
>> +static int fpga_bridge_dev_match(struct device *dev, const void *data)
>> +{
>> +     return dev->parent == data;
>> +}
>> +
>> +/**
>> + * fpga_bridge_get - get an exclusive reference to a fpga bridge
>> + * @dev:     parent device that fpga bridge was registered with
>> + *
>> + * Given a device, get an exclusive reference to a fpga bridge.
>> + *
>> + * Return: fpga manager struct or IS_ERR() condition containing error code.
>> + */
>> +struct fpga_bridge *fpga_bridge_get(struct device *dev,
>> +                                 struct fpga_image_info *info)
>> +{
>> +     struct device *bridge_dev;
>> +
>> +     bridge_dev = class_find_device(fpga_bridge_class, NULL, dev,
>> +                                    fpga_bridge_dev_match);
>> +     if (!bridge_dev)
>> +             return ERR_PTR(-ENODEV);
>> +
>> +     return __fpga_bridge_get(bridge_dev, info);
>> +}
>> +EXPORT_SYMBOL_GPL(fpga_bridge_get);
>
> Do we really need two functions here? Can't we just do a:
>
>         if (dev->of_node)

If we have the device, we might as well find the bridge using the
device.  But if we have the of node, but not the device, we need some
way to get to the device from the of node (can't use container_of).
Such as in the loop in fpga_region_get_bridges() which is going
through the device tree.

>                 dev = class_find_device(fpga_bridge_class, NULL, np,
>                         fpga_bridge_of_node_match);
>         else
>                 dev = class_find_device(fpga_bridge_class, NULL, dev,
>                         fpga_bridge_dev_match);
>
> instead? Maybe you could even move the check into the match function,
> so you can reuse all the code here?

But I agree it would be nice to have one function and if we can make
it work, we should.  We could have one function that takes both a
device node and a device.  If the device is non-null, look it up, else
if the device node is non-node, look it up and return.  If that
doesn't seem ugly and ungainly.

Alan

>
>> +
>>  /**
>>   * fpga_bridge_put - release a reference to a bridge
>>   *
>> @@ -206,7 +240,7 @@ void fpga_bridges_put(struct list_head *bridge_list)
>>  EXPORT_SYMBOL_GPL(fpga_bridges_put);
>>
>>  /**
>> - * fpga_bridges_get_to_list - get a bridge, add it to a list
>> + * of_fpga_bridge_get_to_list - get a bridge, add it to a list
>>   *
>>   * @np: node pointer of a FPGA bridge
>>   * @info: fpga image specific information
>> @@ -216,14 +250,44 @@ EXPORT_SYMBOL_GPL(fpga_bridges_put);
>>   *
>>   * Return 0 for success, error code from of_fpga_bridge_get() othewise.
>>   */
>> -int fpga_bridge_get_to_list(struct device_node *np,
>> +int of_fpga_bridge_get_to_list(struct device_node *np,
>> +                            struct fpga_image_info *info,
>> +                            struct list_head *bridge_list)
>> +{
>> +     struct fpga_bridge *bridge;
>> +     unsigned long flags;
>> +
>> +     bridge = of_fpga_bridge_get(np, info);
>> +     if (IS_ERR(bridge))
>> +             return PTR_ERR(bridge);
>> +
>> +     spin_lock_irqsave(&bridge_list_lock, flags);
>> +     list_add(&bridge->node, bridge_list);
>> +     spin_unlock_irqrestore(&bridge_list_lock, flags);
>> +
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(of_fpga_bridge_get_to_list);
>> +
>> +/**
>> + * fpga_bridge_get_to_list - given device, get a bridge, add it to a list
>> + *
>> + * @dev: FPGA bridge device
>> + * @info: fpga image specific information
>> + * @bridge_list: list of FPGA bridges
>> + *
>> + * Get an exclusive reference to the bridge and and it to the list.
>> + *
>> + * Return 0 for success, error code from fpga_bridge_get() othewise.
>> + */
>> +int fpga_bridge_get_to_list(struct device *dev,
>>                           struct fpga_image_info *info,
>>                           struct list_head *bridge_list)
>>  {
>>       struct fpga_bridge *bridge;
>>       unsigned long flags;
>>
>> -     bridge = of_fpga_bridge_get(np, info);
>> +     bridge = fpga_bridge_get(dev, info);
>>       if (IS_ERR(bridge))
>>               return PTR_ERR(bridge);
>>
>> @@ -381,7 +445,7 @@ static void __exit fpga_bridge_dev_exit(void)
>>  }
>>
>>  MODULE_DESCRIPTION("FPGA Bridge Driver");
>> -MODULE_AUTHOR("Alan Tull <atull@...nsource.altera.com>");
>> +MODULE_AUTHOR("Alan Tull <atull@...nel.org>");
>>  MODULE_LICENSE("GPL v2");
>>
>>  subsys_initcall(fpga_bridge_dev_init);
>> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
>> index d9ab7c7..91755562 100644
>> --- a/drivers/fpga/fpga-region.c
>> +++ b/drivers/fpga/fpga-region.c
>> @@ -183,11 +183,14 @@ static int fpga_region_get_bridges(struct fpga_region *region,
>>       int i, ret;
>>
>>       /* If parent is a bridge, add to list */
>> -     ret = fpga_bridge_get_to_list(region_np->parent, region->info,
>> -                                   &region->bridge_list);
>> +     ret = of_fpga_bridge_get_to_list(region_np->parent, region->info,
>> +                                      &region->bridge_list);
>> +
>> +     /* -EBUSY means parent is a bridge that is under use. Give up. */
>>       if (ret == -EBUSY)
>>               return ret;
>>
>> +     /* Zero return code means parent was a bridge and was added to list. */
>>       if (!ret)
>>               parent_br = region_np->parent;
>>
>> @@ -207,8 +210,8 @@ static int fpga_region_get_bridges(struct fpga_region *region,
>>                       continue;
>>
>>               /* If node is a bridge, get it and add to list */
>> -             ret = fpga_bridge_get_to_list(br, region->info,
>> -                                           &region->bridge_list);
>> +             ret = of_fpga_bridge_get_to_list(br, region->info,
>> +                                              &region->bridge_list);
>>
>>               /* If any of the bridges are in use, give up */
>>               if (ret == -EBUSY) {
>> diff --git a/include/linux/fpga/fpga-bridge.h b/include/linux/fpga/fpga-bridge.h
>> index dba6e3c..9f6696b 100644
>> --- a/include/linux/fpga/fpga-bridge.h
>> +++ b/include/linux/fpga/fpga-bridge.h
>> @@ -42,6 +42,8 @@ struct fpga_bridge {
>>
>>  struct fpga_bridge *of_fpga_bridge_get(struct device_node *node,
>>                                      struct fpga_image_info *info);
>> +struct fpga_bridge *fpga_bridge_get(struct device *dev,
>> +                                 struct fpga_image_info *info);
>>  void fpga_bridge_put(struct fpga_bridge *bridge);
>>  int fpga_bridge_enable(struct fpga_bridge *bridge);
>>  int fpga_bridge_disable(struct fpga_bridge *bridge);
>> @@ -49,9 +51,12 @@ int fpga_bridge_disable(struct fpga_bridge *bridge);
>>  int fpga_bridges_enable(struct list_head *bridge_list);
>>  int fpga_bridges_disable(struct list_head *bridge_list);
>>  void fpga_bridges_put(struct list_head *bridge_list);
>> -int fpga_bridge_get_to_list(struct device_node *np,
>> +int fpga_bridge_get_to_list(struct device *dev,
>>                           struct fpga_image_info *info,
>>                           struct list_head *bridge_list);
>> +int of_fpga_bridge_get_to_list(struct device_node *np,
>> +                            struct fpga_image_info *info,
>> +                            struct list_head *bridge_list);
>>
>>  int fpga_bridge_register(struct device *dev, const char *name,
>>                        const struct fpga_bridge_ops *br_ops, void *priv);
>> --
>> 2.7.4
>>

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