linux-kernel - Re: [PATCH v1 04/16] thunderbolt: ACPI: Use acpi_find_child_by

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Date:   Fri, 10 Jun 2022 09:46:26 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v1 04/16] thunderbolt: ACPI: Use acpi_find_child_by_adr()

On Thu, Jun 09, 2022 at 03:54:40PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Instead of walking the list of children of an ACPI device directly
> in order to find the child matching a given bus address, use
> acpi_find_child_by_adr() for this purpose.
> 
> Apart from simplifying the code, this will help to eliminate the
> children list head from struct acpi_device as it is redundant and it
> is used in questionable ways in some places (in particular, locking is
> needed for walking the list pointed to it safely, but it is often
> missing).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/thunderbolt/acpi.c |    9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> Index: linux-pm/drivers/thunderbolt/acpi.c
> ===================================================================
> --- linux-pm.orig/drivers/thunderbolt/acpi.c
> +++ linux-pm/drivers/thunderbolt/acpi.c
> @@ -304,8 +304,6 @@ static bool tb_acpi_bus_match(struct dev
>  static struct acpi_device *tb_acpi_find_port(struct acpi_device *adev,
>  					     const struct tb_port *port)
>  {
> -	struct acpi_device *port_adev;
> -
>  	if (!adev)
>  		return NULL;
>  
> @@ -313,12 +311,7 @@ static struct acpi_device *tb_acpi_find_
>  	 * Device routers exists under the downstream facing USB4 port
>  	 * of the parent router. Their _ADR is always 0.
>  	 */
> -	list_for_each_entry(port_adev, &adev->children, node) {
> -		if (acpi_device_adr(port_adev) == port->port)
> -			return port_adev;
> -	}
> -
> -	return NULL;
> +	return acpi_find_child_by_adr(adev, port->port);
>  }
>  
>  static struct acpi_device *tb_acpi_switch_find_companion(struct tb_switch *sw)

I don't think you need tb_acpi_find_port() anymore. You can just call
acpi_find_child_by_ard(ACPI_COMPANION(...), port->port) directly, no?

thanks,

-- 
heikki