linux-kernel - Re: [PATCH v5 08/11] devm-helpers: Add resource managed version of debugfs directory create function

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Date: Sun, 24 Mar 2024 16:08:28 +0100
From: Marek Behún <kabel@...nel.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Jonathan.Cameron@...wei.com, Laurent.pinchart@...asonboard.com,
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Subject: Re: [PATCH v5 08/11] devm-helpers: Add resource managed version of
 debugfs directory create function

On Sun, 24 Mar 2024 10:21:28 +0100
Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:

> Le 23/03/2024 à 22:25, Marek Behún a écrit :
> > On Sat, 23 Mar 2024 22:10:40 +0100
> > Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
> >   
> 
> ...
> 
> >>>    static int pvt_ts_dbgfs_create(struct pvt_device *pvt, struct device *dev)
> >>>    {
> >>> -	pvt->dbgfs_dir = debugfs_create_dir(dev_name(dev), NULL);
> >>> +	pvt->dbgfs_dir = devm_debugfs_create_dir(dev, dev_name(dev), NULL);
> >>> +	if (IS_ERR(pvt->dbgfs_dir))
> >>> +		return PTR_ERR(pvt->dbgfs_dir);  
> >>
> >> Not sure if the test and error handling should be added here.
> >> *If I'm correct*, functions related to debugfs already handle this case
> >> and just do nothing. And failure in debugfs related code is not
> >> considered as something that need to be reported and abort a probe function.
> >>
> >> Maybe the same other (already existing) tests in this patch should be
> >> removed as well, in a separated patch.  
> > 
> > Functions related to debugfs maybe do, but devm_ resource management
> > functions may fail to allocate release structure, and those errors need
> > to be handled, AFAIK.  
> 
> I would say no.
> If this memory allocation fails, then debugfs_create_dir() will not be 
> called, but that's not a really big deal if the driver itself can still 
> run normally without it.

debugfs_create_dir() will always be called. Resource allocation is done
afterwards, and if it fails, then the created dir will be removed.

But now I don't know what to do, because yes, it seems that the debugfs
errors are being ignored at many places...

> 
> Up to you to leave it as-is or remove what I think is a useless error 
> handling.
> At least, maybe it could be said in the commit log, so that maintainers 
> can comment on it, if they don't spot the error handling you introduce.
> 
> CJ
> 
> > 
> > Marek
> >   
>