From: Steve Longerbeam <slongerbeam@gmail.com>
To: jacopo mondi <jacopo@jmondi.org>
Cc: linux-media@vger.kernel.org,
"Steve Longerbeam" <steve_longerbeam@mentor.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
"Sakari Ailus" <sakari.ailus@linux.intel.com>,
"Sebastian Reichel" <sre@kernel.org>,
"Hans Verkuil" <hans.verkuil@cisco.com>,
"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 03/17] media: v4l2: async: Add v4l2_async_notifier_add_subdev
Date: Sat, 4 Aug 2018 09:39:30 -0700 [thread overview]
Message-ID: <e465780e-823c-c59e-29d1-f62f3a0e1673@gmail.com> (raw)
In-Reply-To: <20180803151346.GG4528@w540>
Hi Jacopo,
On 08/03/2018 08:13 AM, jacopo mondi wrote:
> Hi Steven,
> I've a small remark, which is probably not only related to your
> patches but was there alreay... Anyway, please read below..
>
>
> On Mon, Jul 09, 2018 at 03:39:03PM -0700, Steve Longerbeam wrote:
>> <snip>
>> +static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
>> +{
>> struct v4l2_async_subdev *asd;
>> int ret;
>> int i;
>> @@ -399,29 +445,25 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
>>
>> mutex_lock(&list_lock);
>>
>> - for (i = 0; i < notifier->num_subdevs; i++) {
>> - asd = notifier->subdevs[i];
>> + if (notifier->subdevs) {
>> + for (i = 0; i < notifier->num_subdevs; i++) {
>> + asd = notifier->subdevs[i];
>>
>> - switch (asd->match_type) {
>> - case V4L2_ASYNC_MATCH_CUSTOM:
>> - case V4L2_ASYNC_MATCH_DEVNAME:
>> - case V4L2_ASYNC_MATCH_I2C:
>> - case V4L2_ASYNC_MATCH_FWNODE:
>> - if (v4l2_async_notifier_has_async_subdev(
>> - notifier, asd, i)) {
>> - dev_err(dev,
>> - "asd has already been registered or in notifier's subdev list\n");
>> - ret = -EEXIST;
>> + ret = v4l2_async_notifier_asd_valid(notifier, asd, i);
>> + if (ret)
>> goto err_unlock;
>> - }
>> - break;
>> - default:
>> - dev_err(dev, "Invalid match type %u on %p\n",
>> - asd->match_type, asd);
>> - ret = -EINVAL;
>> - goto err_unlock;
>> +
>> + list_add_tail(&asd->list, ¬ifier->waiting);
>> + }
>> + } else {
>> + i = 0;
>> + list_for_each_entry(asd, ¬ifier->asd_list, asd_list) {
>> + ret = v4l2_async_notifier_asd_valid(notifier, asd, i++);
> Here the call stack looks like this, if I'm not mistaken:
>
> list_for_each_entry(asd, notifier->asd_list, i) {
> v4l2_async_notifier_asd_valid(notifier, asd, i):
> v4l2_async_notifier_has_async_subdev(notifier, asd, i):
> list_for_each_entry(asd_y, notifier->asd_list, j) {
> if (j >= i) break;
> if (asd == asd_y) return true;
> }
> }
>
> Which is an optimization of O(n^2), but still bad.
>
> This was there already there, it was:
Agreed, it should be safe to remove the check for duplicate
asd's at notifier registration, since this check is done now
in v4l2_async_notifier_add_subdev().
Steve
> for (i = 0; i < notifier->num_subdevs; i++) {
> v4l2_async_notifier_has_async_subdev(notifier, notifier->subdevs[i], i):
> for (j = 0; j < i; j++) {
> if (notifier->subdevs[i] == notifier->subdevs[j])
> return true;
> }
> }
> }
>
> We're not talking high performances here, but I see no reason to go through
> the list twice, as after switching to use your here introduced
> v4l2_async_notifier_add_subdev() async subdevices are tested at endpoint
> parsing time in v4l2_async_notifier_fwnode_parse_endpoint(), which
> guarantees we can't have doubles later, at notifier registration time.
>
> If I'm not wrong, this can be anyway optimized later.
>
> Thanks
> j
>
>
next prev parent reply other threads:[~2018-08-04 16:39 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1531175957-1973-1-git-send-email-steve_longerbeam@mentor.com>
2018-07-09 22:39 ` [PATCH v6 01/17] media: v4l2-fwnode: ignore endpoints that have no remote port parent Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 02/17] media: v4l2: async: Allow searching for asd of any type Steve Longerbeam
2018-09-24 17:06 ` Mauro Carvalho Chehab
2018-09-25 21:04 ` Steve Longerbeam
2018-09-25 22:20 ` Mauro Carvalho Chehab
2018-09-26 1:05 ` Steve Longerbeam
2018-09-26 9:33 ` Mauro Carvalho Chehab
2018-09-26 10:40 ` Sakari Ailus
2018-09-26 17:49 ` Steve Longerbeam
2018-09-28 12:16 ` Sakari Ailus
2018-09-29 17:40 ` Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 03/17] media: v4l2: async: Add v4l2_async_notifier_add_subdev Steve Longerbeam
2018-08-03 15:13 ` jacopo mondi
2018-08-04 16:39 ` Steve Longerbeam [this message]
2018-07-09 22:39 ` [PATCH v6 04/17] media: v4l2: async: Add convenience functions to allocate and add asd's Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 05/17] media: v4l2-fwnode: Switch to v4l2_async_notifier_add_subdev Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 06/17] media: v4l2-fwnode: Add a convenience function for registering subdevs with notifiers Steve Longerbeam
2018-09-13 10:37 ` jacopo mondi
2018-09-13 12:44 ` Sakari Ailus
2018-09-13 12:58 ` jacopo mondi
2018-09-14 0:57 ` Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 07/17] media: platform: video-mux: Register a subdev notifier Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 08/17] media: imx: csi: " Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 09/17] media: imx: mipi csi-2: " Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 10/17] media: staging/imx: of: Remove recursive graph walk Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 11/17] media: staging/imx: Loop through all registered subdevs for media links Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 12/17] media: staging/imx: Rename root notifier Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 13/17] media: staging/imx: Switch to v4l2_async_notifier_add_*_subdev Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 14/17] media: staging/imx: TODO: Remove one assumption about OF graph parsing Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 16/17] media: v4l2: async: Remove notifier subdevs array Steve Longerbeam
2018-07-23 12:35 ` Sakari Ailus
2018-07-23 16:44 ` Steve Longerbeam
2018-07-23 17:24 ` Sakari Ailus
2018-08-04 10:33 ` jacopo mondi
2018-08-04 17:20 ` Steve Longerbeam
2018-07-09 22:39 ` [PATCH v6 17/17] [media] v4l2-subdev.rst: Update doc regarding subdev descriptors Steve Longerbeam
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