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From: Markus Armbruster <armbru@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v4 08/23] qdev: Introduce
	qdev_iterate_recursive
References: <cover.1276641524.git.jan.kiszka@web.de>
	<cover.1276641524.git.jan.kiszka@web.de>
	<8f4efb5aab7b6cd6bca60816059dd38e77c6a1ff.1276641524.git.jan.kiszka@web.de>
Date: Wed, 23 Jun 2010 11:40:37 +0200
In-Reply-To: <8f4efb5aab7b6cd6bca60816059dd38e77c6a1ff.1276641524.git.jan.kiszka@web.de>
	(Jan Kiszka's message of "Wed, 16 Jun 2010 00:38:32 +0200")
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Juan Quintela <quintela@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>, Blue Swirl <blauwirbel@gmail.com>, Avi Kivity <avi@redhat.com>

Jan Kiszka <jan.kiszka@web.de> writes:

> From: Jan Kiszka <jan.kiszka@siemens.com>
>
> Add qdev_iterate_recursive to walk the complete qtree invoking a
> callback for each device. Use this service to implement
> qdev_find_id_recursive.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  hw/qdev.c |   29 +++++++++++++++++++++++++----
>  hw/qdev.h |    3 +++
>  2 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/hw/qdev.c b/hw/qdev.c
> index 2d1d171..466d8d5 100644
> --- a/hw/qdev.c
> +++ b/hw/qdev.c
> @@ -475,16 +475,22 @@ static BusState *qbus_find_recursive(BusState *bus, const char *name,
>      return NULL;
>  }
>  
> -static DeviceState *qdev_find_id_recursive(BusState *bus, const char *id)
> +void *qdev_iterate_recursive(BusState *bus, qdev_iteratefn callback,
> +                             void *opaque)
>  {
>      DeviceState *dev, *ret;
>      BusState *child;
>  
> +    if (!bus) {
> +        bus = main_system_bus;
> +    }
>      QTAILQ_FOREACH(dev, &bus->children, sibling) {
> -        if (dev->id && strcmp(dev->id, id) == 0)
> -            return dev;
> +        ret = callback(dev, opaque);
> +        if (ret) {
> +            return ret;
> +        }
>          QTAILQ_FOREACH(child, &dev->child_bus, sibling) {
> -            ret = qdev_find_id_recursive(child, id);
> +            ret = qdev_iterate_recursive(child, callback, opaque);
>              if (ret) {
>                  return ret;
>              }

I'd call "iterate recursive" simply "walk".  It's common usage for
trees.

Except this isn't a walk or iteration, it's a search: the walk stops as
soon as the callback returns non-null.  Not obvious from the name,
therefore needs a comment.

[...]