linux-kernel - Re: [PATCH v2 05/16] USB: ACPI: Replace usb_acpi_find_port() with acpi_find_child_by

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Date:   Mon, 13 Jun 2022 21:53:33 +0300
From:   Andy Shevchenko <andriy.shevchenko@...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>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 05/16] USB: ACPI: Replace usb_acpi_find_port() with
 acpi_find_child_by_adr()

On Mon, Jun 13, 2022 at 08:39:37PM +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.
> 
> Also notice that if acpi_find_child_by_adr() doesn't find a matching
> child, acpi_find_child_device() will not find it too, so directly
> replace usb_acpi_find_port() in usb_acpi_get_companion_for_port() with
> acpi_find_child_by_adr() and drop it entirely.
> 
> 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).

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> v1 -> v2:
>    * Drop usb_acpi_find_port() (Heikki, Andy).
>    * Change the subject accordingly.
> 
> ---
>  drivers/usb/core/usb-acpi.c |   18 +-----------------
>  1 file changed, 1 insertion(+), 17 deletions(-)
> 
> Index: linux-pm/drivers/usb/core/usb-acpi.c
> ===================================================================
> --- linux-pm.orig/drivers/usb/core/usb-acpi.c
> +++ linux-pm/drivers/usb/core/usb-acpi.c
> @@ -124,22 +124,6 @@ out:
>   */
>  #define USB_ACPI_LOCATION_VALID (1 << 31)
>  
> -static struct acpi_device *usb_acpi_find_port(struct acpi_device *parent,
> -					      int raw)
> -{
> -	struct acpi_device *adev;
> -
> -	if (!parent)
> -		return NULL;
> -
> -	list_for_each_entry(adev, &parent->children, node) {
> -		if (acpi_device_adr(adev) == raw)
> -			return adev;
> -	}
> -
> -	return acpi_find_child_device(parent, raw, false);
> -}
> -
>  static struct acpi_device *
>  usb_acpi_get_companion_for_port(struct usb_port *port_dev)
>  {
> @@ -170,7 +154,7 @@ usb_acpi_get_companion_for_port(struct u
>  		port1 = port_dev->portnum;
>  	}
>  
> -	return usb_acpi_find_port(adev, port1);
> +	return acpi_find_child_by_adr(adev, port1);
>  }
>  
>  static struct acpi_device *
> 
> 
> 

-- 
With Best Regards,
Andy Shevchenko