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

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Message-ID: <20180926104038.tc3u7vzojumcthen@kekkonen.localdomain>
Date:   Wed, 26 Sep 2018 13:40:39 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc:     Steve Longerbeam <steve_longerbeam@...tor.com>,
        Steve Longerbeam <slongerbeam@...il.com>,
        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 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?

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.

> 
> Haven't write myself any piece of code using async framework, on a first
> glance, trying to register twice sounds like an error to me.
> 
> Sakari, what do you think?

-- 
Regards,

Sakari Ailus
sakari.ailus@...ux.intel.com