linux-kernel - Re: [PATCH v1 1/2] driver core: fw_devlink: Allow firmware to mark devices as best effort

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Date:   Thu, 23 Jun 2022 08:50:31 +0200
From:   Sascha Hauer <sha@...gutronix.de>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Len Brown <lenb@...nel.org>, Peng Fan <peng.fan@....com>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-gpio@...r.kernel.org, kernel@...gutronix.de,
        devicetree@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v1 1/2] driver core: fw_devlink: Allow firmware to mark
 devices as best effort

On Wed, Jun 22, 2022 at 02:59:10PM -0700, Saravana Kannan wrote:
> When firmware sets the FWNODE_FLAG_BEST_EFFORT flag for a fwnode,
> fw_devlink will do a best effort ordering for that device where it'll
> only enforce the probe/suspend/resume ordering of that device with
> suppliers that have drivers. The driver of that device can then decide
> if it wants to defer probe or probe without the suppliers.
> 
> This will be useful for avoid probe delays of the console device that
> were caused by commit 71066545b48e ("driver core: Set
> fw_devlink.strict=1 by default").
> 
> Fixes: 71066545b48e ("driver core: Set fw_devlink.strict=1 by default")
> Reported-by: Sascha Hauer <sha@...gutronix.de>
> Reported-by: Peng Fan <peng.fan@....com>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c    | 3 ++-
>  include/linux/fwnode.h | 4 ++++
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 839f64485a55..61edd18b7bf3 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -968,7 +968,8 @@ static void device_links_missing_supplier(struct device *dev)
>  
>  static bool dev_is_best_effort(struct device *dev)
>  {
> -	return fw_devlink_best_effort && dev->can_match;
> +	return (fw_devlink_best_effort && dev->can_match) ||
> +		dev->fwnode->flags & FWNODE_FLAG_BEST_EFFORT;

Check for dev->fwnode first. I am running in a NULL pointer exception
here for a device that doesn't have a fwnode.

Sascha


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