linux-kernel - Re: [PATCH] driver core: Don't log intentional skip of device link creation as error

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Date: Mon, 24 Jun 2024 16:53:30 -0700
From: Saravana Kannan <saravanak@...gle.com>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, kernel@...labora.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver core: Don't log intentional skip of device link
 creation as error

On Mon, Jun 24, 2024 at 8:21 AM Nícolas F. R. A. Prado
<nfraprado@...labora.com> wrote:
>
> Commit ac66c5bbb437 ("driver core: Allow only unprobed consumers for
> SYNC_STATE_ONLY device links") introduced an early return in
> device_link_add() to prevent useless links from being created. However
> the calling function fw_devlink_create_devlink() unconditionally prints
> an error if device_link_add() didn't create a link, even in this case
> where it is intentionally skipping the link creation.
>
> Add a check to detect if the link wasn't created intentionally and in
> that case don't log an error.

Your point is somewhat valid, and I might Ack this. But this really
shouldn't be happening a lot. Can you give more context on how you are
hitting this?

There might be a better way to filter things out.

-Saravana

>
> Fixes: ac66c5bbb437 ("driver core: Allow only unprobed consumers for SYNC_STATE_ONLY device links")
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> ---
>  drivers/base/core.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 2b4c0624b704..5eaafe3a280c 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2187,8 +2187,13 @@ static int fw_devlink_create_devlink(struct device *con,
>                 }
>
>                 if (con != sup_dev && !device_link_add(con, sup_dev, flags)) {
> -                       dev_err(con, "Failed to create device link (0x%x) with %s\n",
> -                               flags, dev_name(sup_dev));
> +                       if (flags & DL_FLAG_SYNC_STATE_ONLY &&
> +                           con->links.status != DL_DEV_NO_DRIVER &&
> +                           con->links.status != DL_DEV_PROBING)
> +                               dev_dbg(con, "Skipping device link creation for probed device\n");
> +                       else
> +                               dev_err(con, "Failed to create device link (0x%x) with %s\n",
> +                                       flags, dev_name(sup_dev));
>                         ret = -EINVAL;
>                 }
>
>
> ---
> base-commit: b992b79ca8bc336fa8e2c80990b5af80ed8f36fd
> change-id: 20240624-fwdevlink-probed-no-err-45d21feb05fd
>
> Best regards,
> --
> Nícolas F. R. A. Prado <nfraprado@...labora.com>
>