linux-kernel - Re: [PATCH RESEND] of: add const to struct of_device

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Message-ID: <20120624144320.GB28001@pengutronix.de>
Date:	Sun, 24 Jun 2012 16:43:20 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	kernel@...gutronix.de,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [PATCH RESEND] of: add const to struct of_device_id.data

Hello Arnd,

On Fri, Jun 22, 2012 at 05:26:22PM +0000, Arnd Bergmann wrote:
> On Friday 22 June 2012, Uwe Kleine-König wrote:
> > On Thu, Jun 07, 2012 at 12:20:14PM +0200, Uwe Kleine-König wrote:
> > > Drivers should never need to modify the data of a device id. So it can
> > > be const which in turn allows more consts in the driver.
> > > 
> > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > > ---
> > > (Cc += lkml + Grant)
> > > 
> > > Hello,
> > > 
> > > this might introduce warnings in drivers that access the data member
> > > without using const, so this is definitly merge window material if it is
> > > considered at all.
> >
> > ping
> 
> Sorry for the delayed response. I think the approach is right, but I
> am a bit worried about adding warnings for legit code.
> 
> A quick test with the defconfigs gave me this error for prima2_defconfig
> and kzm9g_defconfig:
> 
> /home/arnd/linux-arm/arch/arm/mm/cache-l2x0.c: In function 'l2x0_of_init':
> /home/arnd/linux-arm/arch/arm/mm/cache-l2x0.c:573:7: error: assignment discards 'const' qualifier from pointer target type [-Werror]
I already sent a patch for that to rmk's patch system:

	http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7429/1

Russell commented: 
Sigh, a gmane.org URL.  Which is difficult to dig the thread out of.
Eventually you can.  And I see nothing which suggests that the series
will be applied or, more importantly when it is going to be applied.
Punting this patch until there's better communication.

Russell, I didn't completely get your problem about gmane here. If you
follow the link in the Subject: line, you get a thread view. Does this
address your concerns?

And even without the of: add const to struct of_device_id.data patch
patch using more consts is IMHO nice.

> and this one with at91sam9263_defconfig:
> /home/arnd/linux-arm/drivers/misc/atmel_tclib.c: In function 'tc_probe':
> /home/arnd/linux-arm/drivers/misc/atmel_tclib.c:170:19: error: assignment discards 'const' qualifier from pointer target type [-Werror]
> 
> I haven't checked all the defconfigs yet, but I think we should at least
> make sure they build fine before applying your patch.
Fine for me, I will come up with a series next week.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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