linux-kernel - Re: [PATCH v2 04/16] thunderbolt: ACPI: Replace tb_acpi_find_port() with acpi_find_child_by

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Date:   Tue, 14 Jun 2022 10:36:05 +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 v2 04/16] thunderbolt: ACPI: Replace tb_acpi_find_port()
 with acpi_find_child_by_adr()

On Mon, Jun 13, 2022 at 08:11:36PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Use acpi_find_child_by_adr() to find the child matching a given bus
> address instead of tb_acpi_find_port() that walks the list of children
> of an ACPI device directly for this purpose and drop the latter.
> 
> 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>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
> 
> v1 -> v2:
>    * Drop tb_acpi_find_port() (Heikki, Andy).
>    * Change the subject accordingly
> 
> ---
>  drivers/thunderbolt/acpi.c |   27 ++++-----------------------
>  1 file changed, 4 insertions(+), 23 deletions(-)
> 
> Index: linux-pm/drivers/thunderbolt/acpi.c
> ===================================================================
> --- linux-pm.orig/drivers/thunderbolt/acpi.c
> +++ linux-pm/drivers/thunderbolt/acpi.c
> @@ -301,26 +301,6 @@ static bool tb_acpi_bus_match(struct dev
>  	return tb_is_switch(dev) || tb_is_usb4_port_device(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;
> -
> -	/*
> -	 * 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;
> -}
> -
>  static struct acpi_device *tb_acpi_switch_find_companion(struct tb_switch *sw)
>  {
>  	struct acpi_device *adev = NULL;
> @@ -331,7 +311,8 @@ static struct acpi_device *tb_acpi_switc
>  		struct tb_port *port = tb_port_at(tb_route(sw), parent_sw);
>  		struct acpi_device *port_adev;
>  
> -		port_adev = tb_acpi_find_port(ACPI_COMPANION(&parent_sw->dev), port);
> +		port_adev = acpi_find_child_by_adr(ACPI_COMPANION(&parent_sw->dev),
> +						   port->port);
>  		if (port_adev)
>  			adev = acpi_find_child_device(port_adev, 0, false);
>  	} else {
> @@ -364,8 +345,8 @@ static struct acpi_device *tb_acpi_find_
>  	if (tb_is_switch(dev))
>  		return tb_acpi_switch_find_companion(tb_to_switch(dev));
>  	else if (tb_is_usb4_port_device(dev))
> -		return tb_acpi_find_port(ACPI_COMPANION(dev->parent),
> -					 tb_to_usb4_port_device(dev)->port);
> +		return acpi_find_child_by_adr(ACPI_COMPANION(dev->parent),
> +					      tb_to_usb4_port_device(dev)->port->port);
>  	return NULL;
>  }
>  
> 
> 

-- 
heikki