linux-kernel - Re: [PATCH v1 14/18] driver core: Use device's fwnode to check if it is waiting for suppliers

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Date:   Mon, 16 Nov 2020 17:34:41 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v1 14/18] driver core: Use device's fwnode to check if it
 is waiting for suppliers

On Thu, Nov 5, 2020 at 12:24 AM Saravana Kannan <saravanak@...gle.com> wrote:
>
> To check if a device is still waiting for its supplier devices to be
> added, we used to check if the devices is in a global
> waiting_for_suppliers list. Since the global list will be deleted in
> subsequent patches, this patch stops using this check.

My kind of educated guess is that you want to drop
waiting_for_suppliers and that's why you want to use supplier links
here.

>
> Instead, this patch uses a more device specific check. It checks if the
> device's fwnode has any fwnode links that haven't been converted to
> device links yet.
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 4ae5f2885ac5..d51dd564add1 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -51,6 +51,7 @@ static DEFINE_MUTEX(wfs_lock);
>  static LIST_HEAD(deferred_sync);
>  static unsigned int defer_sync_state_count = 1;
>  static DEFINE_MUTEX(fwnode_link_lock);
> +static bool fw_devlink_is_permissive(void);
>
>  /**
>   * fwnode_link_add - Create a link between two fwnode_handles.
> @@ -994,13 +995,13 @@ int device_links_check_suppliers(struct device *dev)
>          * Device waiting for supplier to become available is not allowed to
>          * probe.
>          */
> -       mutex_lock(&wfs_lock);
> -       if (!list_empty(&dev->links.needs_suppliers) &&
> -           dev->links.need_for_probe) {
> -               mutex_unlock(&wfs_lock);
> +       mutex_lock(&fwnode_link_lock);
> +       if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
> +           !fw_devlink_is_permissive()) {
> +               mutex_unlock(&fwnode_link_lock);
>                 return -EPROBE_DEFER;
>         }
> -       mutex_unlock(&wfs_lock);
> +       mutex_unlock(&fwnode_link_lock);
>
>         device_links_write_lock();
>
> @@ -1166,10 +1167,7 @@ static ssize_t waiting_for_supplier_show(struct device *dev,
>         bool val;
>
>         device_lock(dev);
> -       mutex_lock(&wfs_lock);
> -       val = !list_empty(&dev->links.needs_suppliers)
> -             && dev->links.need_for_probe;
> -       mutex_unlock(&wfs_lock);

Why isn't the lock needed any more?

Or maybe it wasn't needed previously too?

> +       val = !list_empty(&dev->fwnode->suppliers);
>         device_unlock(dev);
>         return sysfs_emit(buf, "%u\n", val);
>  }
> @@ -2226,7 +2224,7 @@ static int device_add_attrs(struct device *dev)
>                         goto err_remove_dev_groups;
>         }
>
> -       if (fw_devlink_flags && !fw_devlink_is_permissive()) {
> +       if (fw_devlink_flags && !fw_devlink_is_permissive() && dev->fwnode) {

And why is this change needed?

>                 error = device_create_file(dev, &dev_attr_waiting_for_supplier);
>                 if (error)
>                         goto err_remove_dev_online;
> --
> 2.29.1.341.ge80a0c044ae-goog
>