Date:   Thu, 6 Jul 2017 13:53:23 -0500
From:   Alan Tull <atull@...nel.org>
To:     Anatolij Gustschin <agust@...x.de>
Cc:     Moritz Fischer <moritz.fischer@...us.com>,
        linux-fpga@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fpga manager: add notifier for manager register and
 unregister events

On Thu, Jul 6, 2017 at 11:02 AM, Anatolij Gustschin <agust@...x.de> wrote:
> Add API functions for registering and removing a notifier for FPGA
> manager register/unregister events. Notify when a new FPGA manager
> has been registered or when an existing manager is being removed.
> This will help configuration interface drivers to get the notion
> of low-level FPGA managers popping up or disappearing, when using
> hotpluggable FPGA configuration devices (e.g. via USB-SPI adapters).
>

Hi Anatolij,

This is interesting and looks pretty straightforward.  Do you have any
code that uses it?

Alan

> Signed-off-by: Anatolij Gustschin <agust@...x.de>
> ---
>  Documentation/fpga/fpga-mgr.txt |  8 ++++++++
>  drivers/fpga/fpga-mgr.c         | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/fpga/fpga-mgr.h   | 13 +++++++++++++
>  3 files changed, 55 insertions(+)
>
> diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
> index 78f197f..e81d566 100644
> --- a/Documentation/fpga/fpga-mgr.txt
> +++ b/Documentation/fpga/fpga-mgr.txt
> @@ -73,6 +73,14 @@ Use of these two functions is described below in "How To Support a new FPGA
>  device."
>
>
> +To register or unregister the notifier callback for signalling
> +about the low level FPGA-Managers being added or removed:
> +----------------------------------------------------------
> +
> +       void fpga_mgr_register_mgr_notifier(struct notifier_block *nb);
> +       void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb);
> +
> +
>  How to write an image buffer to a supported FPGA
>  ================================================
>  /* Include to get the API */
> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
> index 188ffef..7362bb4 100644
> --- a/drivers/fpga/fpga-mgr.c
> +++ b/drivers/fpga/fpga-mgr.c
> @@ -27,10 +27,39 @@
>  #include <linux/slab.h>
>  #include <linux/scatterlist.h>
>  #include <linux/highmem.h>
> +#include <linux/notifier.h>
>
>  static DEFINE_IDA(fpga_mgr_ida);
>  static struct class *fpga_mgr_class;
>
> +static BLOCKING_NOTIFIER_HEAD(fpga_mgr_notifier_list);
> +
> +/**
> + * fpga_mgr_register_mgr_notifier() - register fpga manager notifier callback
> + * @nb: pointer to the notifier block for the callback events.
> + *
> + * Add a notifier callback for FPGA manager changes. These changes are
> + * either FPGA manager being added or removed.
> + */
> +void fpga_mgr_register_mgr_notifier(struct notifier_block *nb)
> +{
> +       blocking_notifier_chain_register(&fpga_mgr_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(fpga_mgr_register_mgr_notifier);
> +
> +/**
> + * fpga_mgr_unregister_mgr_notifier() - unregister a notifier callback
> + * @nb: pointer to the notifier block for the callback events.
> + *
> + * Remove a notifier callback. fpga_mgr_register_mgr_notifier() must have
> + * been previously called for this function to work properly.
> + */
> +void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb)
> +{
> +       blocking_notifier_chain_unregister(&fpga_mgr_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(fpga_mgr_unregister_mgr_notifier);
> +
>  /*
>   * Call the low level driver's write_init function.  This will do the
>   * device-specific things to get the FPGA into the state where it is ready to
> @@ -518,6 +547,8 @@ int fpga_mgr_register(struct device *dev, const char *name,
>
>         dev_info(&mgr->dev, "%s registered\n", mgr->name);
>
> +       blocking_notifier_call_chain(&fpga_mgr_notifier_list,
> +                                    FPGA_MGR_ADD, mgr);
>         return 0;
>
>  error_device:
> @@ -539,6 +570,9 @@ void fpga_mgr_unregister(struct device *dev)
>
>         dev_info(&mgr->dev, "%s %s\n", __func__, mgr->name);
>
> +       blocking_notifier_call_chain(&fpga_mgr_notifier_list,
> +                                    FPGA_MGR_REMOVE, mgr);
> +
>         /*
>          * If the low level driver provides a method for putting fpga into
>          * a desired state upon unregister, do it.
> diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
> index b4ac24c..7ed4f68 100644
> --- a/include/linux/fpga/fpga-mgr.h
> +++ b/include/linux/fpga/fpga-mgr.h
> @@ -17,6 +17,7 @@
>   */
>  #include <linux/mutex.h>
>  #include <linux/platform_device.h>
> +#include <linux/notifier.h>
>
>  #ifndef _LINUX_FPGA_MGR_H
>  #define _LINUX_FPGA_MGR_H
> @@ -154,4 +155,16 @@ int fpga_mgr_register(struct device *dev, const char *name,
>
>  void fpga_mgr_unregister(struct device *dev);
>
> +/*
> + * FPGA Manager register notifier events
> + * FPGA_MGR_ADD: a new fpga manager has been registered
> + * FPGA_MGR_REMOVE: a registered fpga manager is being removed
> + */
> +#define FPGA_MGR_ADD   1
> +#define FPGA_MGR_REMOVE        2
> +
> +void fpga_mgr_register_mgr_notifier(struct notifier_block *nb);
> +
> +void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb);
> +
>  #endif /*_LINUX_FPGA_MGR_H */
> --
> 2.7.4
>
> --
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