linux-kernel - Re: [PATCH v1] driver core: fw_devlink: Don't create device links for devices not on a bus

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Date:   Wed, 1 Sep 2021 08:24:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] driver core: fw_devlink: Don't create device links
 for devices not on a bus

On Tue, Aug 31, 2021 at 03:45:10PM -0700, Saravana Kannan wrote:
> Devices that are not on a bus will never have a driver bound to it. So,
> fw_devlink should not create device links for it as it can cause probe
> issues[1] or sync_state() call back issues[2].
> 
> [1] - https://lore.kernel.org/lkml/CAGETcx_xJCqOWtwZ9Ee2+0sPGNLM5=F=djtbdYENkAYZa0ynqQ@mail.gmail.com/
> [2] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/
> Fixes: f9aa460672c9 ("driver core: Refactor fw_devlink feature")
> Reported-by: Ulf Hansson <ulf.hansson@...aro.org>
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index f6360490a4a3..304a06314656 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1719,8 +1719,24 @@ static int fw_devlink_create_devlink(struct device *con,
>  	struct device *sup_dev;
>  	int ret = 0;
>  
> +	/*
> +	 * If a consumer device is not on a bus (i.e. a driver will never bind
> +	 * to it), it doesn't make sense for fw_devlink to create device links
> +	 * for it.
> +	 */
> +	if (con->bus == NULL)
> +		return -EINVAL;
> +

Why would a device not be on a bus that has to do with a driver needing
it?  What types of devices are these?

thanks,

greg k-h