linux-kernel - Re: [PATCH v2 2/4] input: keyboard: tegra: use devm

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Message-ID: <20130109092352.GA28037@avionic-0098.adnet.avionic-design.de>
Date:	Wed, 9 Jan 2013 10:23:52 +0100
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Laxman Dewangan <ldewangan@...dia.com>, grant.likely@...retlab.ca,
	rob.herring@...xeda.com, swarren@...dia.com,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	linux-tegra@...r.kernel.org, Wolfram Sang <w.sang@...gutronix.de>
Subject: Re: [PATCH v2 2/4] input: keyboard: tegra: use devm_* for resource
 allocation

On Wed, Jan 09, 2013 at 01:19:39AM -0800, Dmitry Torokhov wrote:
> On Wed, Jan 09, 2013 at 08:07:45AM +0100, Thierry Reding wrote:
> > On Sun, Jan 06, 2013 at 11:57:48AM -0800, Dmitry Torokhov wrote:
> > > On Sun, Jan 06, 2013 at 08:27:39PM +0100, Thierry Reding wrote:
> > > > On Sat, Jan 05, 2013 at 12:06:58AM -0800, Dmitry Torokhov wrote:
> > > > > On Sat, Jan 05, 2013 at 01:15:08PM +0530, Laxman Dewangan wrote:
> > > > [...]
> > > > > > @@ -735,25 +738,16 @@ static int tegra_kbc_probe(struct platform_device *pdev)
> > > > > >  	spin_lock_init(&kbc->lock);
> > > > > >  	setup_timer(&kbc->timer, tegra_kbc_keypress_timer, (unsigned long)kbc);
> > > > > >  
> > > > > > -	res = request_mem_region(res->start, resource_size(res), pdev->name);
> > > > > > -	if (!res) {
> > > > > > -		dev_err(&pdev->dev, "failed to request I/O memory\n");
> > > > > > -		err = -EBUSY;
> > > > > > -		goto err_free_mem;
> > > > > > -	}
> > > > > > -
> > > > > > -	kbc->mmio = ioremap(res->start, resource_size(res));
> > > > > > +	kbc->mmio = devm_request_and_ioremap(&pdev->dev, res);
> > > > > >  	if (!kbc->mmio) {
> > > > > > -		dev_err(&pdev->dev, "failed to remap I/O memory\n");
> > > > > > -		err = -ENXIO;
> > > > > > -		goto err_free_mem_region;
> > > > > > +		dev_err(&pdev->dev, "Cannot request memregion/iomap address\n");
> > > > > > +		return -EADDRNOTAVAIL;
> > > > > 
> > > > > Erm, no, -EBUSY please.
> > > > 
> > > > EADDRNOTAVAIL is the canonical error for devm_request_and_ioremap()
> > > > failure. The kerneldoc comment in lib/devres.c even gives a short
> > > > example that uses this error code.
> > > 
> > > I am sorry, but I do not consider a function that was added a little
> > > over a year ago as a canon. If you look at the uses of EADDRNOTAVAIL it
> > > is used predominantly in networking code to indicate that attempted
> > > _network_ address is not available.
> > 
> > EBUSY might be misleading, though. devm_request_and_ioremap() can fail
> > in both the request_mem_region() and ioremap() calls. Furthermore it'd
> > be good to settle on a consistent error-code instead of doing it
> > differently depending on subsystem and/or driver. Currently the various
> > error codes used are:
> > 
> > 	EBUSY, EADDRNOTAVAIL, ENXIO, ENOMEM, ENODEV, ENOENT, EINVAL,
> > 	EIO, EFAULT, EADDRINUSE
> > 
> > Also if we can settle on one error code we should follow up with a patch
> > to make it consistent across the tree and also update that kerneldoc
> > comment. I volunteer to do that if nobody else steps up. I'm also Cc'ing
> > Wolfram (the original author), maybe he has some thoughts on this.
> > 
> 
> If you going to change all drivers make devm_request_and_ioremap()
> return ERR_PTR()-encoded errors and then we can differentiate what
> part of it failed.

Yeah, that thought also crossed my mind. I'll give other people some
time to comment before hurling myself into preparing patches.

Thierry

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