linux-kernel - Re: [PATCH v1 09/18] driver core: Allow only unprobed consumers for SYNC_STATE

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Date:   Mon, 16 Nov 2020 16:57:15 +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 09/18] driver core: Allow only unprobed consumers for
 SYNC_STATE_ONLY device links

On Thu, Nov 5, 2020 at 12:24 AM Saravana Kannan <saravanak@...gle.com> wrote:
>
> SYNC_STATE_ONLY device links only affect the behavior of sync_state()
> callbacks. Specifically, they prevent sync_state() only callbacks from
> being called on a device if one or more of its consumers haven't probed.
>
> So, creating a SYNC_STATE_ONLY device link from an already probed
> consumer is useless. So, don't allow creating such device links.

I'm wondering why this needs to be part of the series?

It looks like it could go in separately, couldn't it?

>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 1a1d9a55645c..4a0907574646 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -646,6 +646,17 @@ struct device_link *device_link_add(struct device *consumer,
>                 goto out;
>         }
>
> +       /*
> +        * SYNC_STATE_ONLY links are useless once a consumer device has probed.
> +        * So, only create it if the consumer hasn't probed yet.
> +        */
> +       if (flags & DL_FLAG_SYNC_STATE_ONLY &&
> +           consumer->links.status != DL_DEV_NO_DRIVER &&
> +           consumer->links.status != DL_DEV_PROBING) {
> +               link = NULL;
> +               goto out;
> +       }

Returning NULL at this point may be confusing if there is a link
between these devices already.

> +
>         /*
>          * DL_FLAG_AUTOREMOVE_SUPPLIER indicates that the link will be needed
>          * longer than for DL_FLAG_AUTOREMOVE_CONSUMER and setting them both
> --
> 2.29.1.341.ge80a0c044ae-goog
>