linux-kernel - Re: [PATCH v6 02/17] media: v4l2: async: Allow searching for asd of any type

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Date:   Sat, 29 Sep 2018 10:40:28 -0700
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Sakari Ailus <sakari.ailus@....fi>,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        linux-media@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sebastian Reichel <sre@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 02/17] media: v4l2: async: Allow searching for asd of
 any type

Hi Sakari,


On 09/28/2018 05:16 AM, Sakari Ailus wrote:
> On Wed, Sep 26, 2018 at 10:49:18AM -0700, Steve Longerbeam wrote:
>> Hi Mauro, Sakari,
>>
>>
>> On 09/26/2018 03:40 AM, Sakari Ailus wrote:
>>> Hi Mauro, Steve,
>>>
>>> On Wed, Sep 26, 2018 at 06:33:35AM -0300, Mauro Carvalho Chehab wrote:
>>>> Em Tue, 25 Sep 2018 18:05:36 -0700
>>>> Steve Longerbeam <steve_longerbeam@...tor.com> escreveu:
>>>>
>>>>> On 09/25/2018 03:20 PM, Mauro Carvalho Chehab wrote:
>>>>>> Em Tue, 25 Sep 2018 14:04:21 -0700
>>>>>> Steve Longerbeam <steve_longerbeam@...tor.com> escreveu:
>>>>>>>>> @@ -392,12 +406,11 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
>>>>>>>>>      		case V4L2_ASYNC_MATCH_CUSTOM:
>>>>>>>>>      		case V4L2_ASYNC_MATCH_DEVNAME:
>>>>>>>>>      		case V4L2_ASYNC_MATCH_I2C:
>>>>>>>>> -			break;
>>>>>>>>>      		case V4L2_ASYNC_MATCH_FWNODE:
>>>>>>>>> -			if (v4l2_async_notifier_fwnode_has_async_subdev(
>>>>>>>>> -				    notifier, asd->match.fwnode, i)) {
>>>>>>>>> +			if (v4l2_async_notifier_has_async_subdev(
>>>>>>>>> +				    notifier, asd, i)) {
>>>>>>>>>      				dev_err(dev,
>>>>>>>>> -					"fwnode has already been registered or in notifier's subdev list\n");
>>>>>>>>> +					"asd has already been registered or in notifier's subdev list\n");
>>>>>>>> Please, never use "asd" on messages printed to the user. While someone
>>>>>>>> may understand it while reading the source code, for a poor use,
>>>>>>>> "asd" is just a random sequence of 3 characters.
>>>>>>> I will change the message to read:
>>>>>>>
>>>>>>> "subdev descriptor already listed in this or other notifiers".
>>>>>> Perfect!
>>>>> But the error message is removed in the subsequent patch
>>>>> "[PATCH 03/17] media: v4l2: async: Add v4l2_async_notifier_add_subdev".
>>>>>
>>>>> I could bring it back as a dev_dbg() in v4l2_async_notifier_asd_valid(), but
>>>>> this shouldn't be a dev_err() anymore since it is up to the media platform
>>>>> to decide whether an already existing subdev descriptor is an error.
>>>> Hmm... that's an interesting discussion... what cases do you think it
>>>> would be fine to try to register twice an asd notifier?
>> It should be a fairly common case that a sub-device has multiple fwnode
>> output ports. In that case it's possible multiple sub-devices downstream
>> from it will each encounter it when parsing the fwnode graph, and attempt
>> to add it to their notifiers asd_list multiple times. That isn't an error,
>> any
>> attempt to add it after the first add should be ignored.
>>
>> imx-media is an example, there is a CSI-2 transmitter with four fwnode
>> output ports for each CSI-2 virtual channel. Those channels each go to
>> one of four Camera Sensor Interface in the imx6 IPU. So each CSI will
>> encounter the CSI-2 transmitter when parsing its fwnode ports.
>>
>>
>>> Only the error message is removed; this case is still considered an error.
>>> I think it'd be better to keep this error message; it helps debugging.
>> Ok I will add it back, but it should be a dev_dbg().
> Fine for me.
>
> Could you address especially the author vs. SoB line difference in the set,
> and re-post to the list, please?

Will do!

>
> I've pushed the latest set including my fwnode patches (which you can
> ignore) to my linuxtv.org tree v4l2-fwnode branch; feel free to use these
> as the basis. I've fixed a few conflicts in there in rebasing on current
> media tree master.

Yes in drivers/media/platform/ti-vpe/cal.c, due to

58513d4849 (" media: platform: remove redundant null pointer check 
before of_node_put")

I fixed that conflict too, but in a different way that retains the above 
change.

Since my conflict fix is different from yours, I will push v7 against 
current
media tree master. Let me know if the fixup looks ok to you.

Steve