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SubjectRe: [PATCH RESEND] of: add const to struct of_device_id.data
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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@pengutronix.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]

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.

Arnd

8<---
diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
index 2a8e380..577baf7 100644
--- a/arch/arm/mm/cache-l2x0.c
+++ b/arch/arm/mm/cache-l2x0.c
@@ -554,7 +554,7 @@ static const struct of_device_id l2x0_ids[] __initconst = {
int __init l2x0_of_init(u32 aux_val, u32 aux_mask)
{
struct device_node *np;
- struct l2x0_of_data *data;
+ const struct l2x0_of_data *data;
struct resource res;

np = of_find_matching_node(NULL, l2x0_ids);
diff --git a/include/linux/atmel_tc.h b/include/linux/atmel_tc.h
index 1d14b1dc..89a931b 100644
--- a/include/linux/atmel_tc.h
+++ b/include/linux/atmel_tc.h
@@ -63,7 +63,7 @@ struct atmel_tc {
struct platform_device *pdev;
struct resource *iomem;
void __iomem *regs;
- struct atmel_tcb_config *tcb_config;
+ const struct atmel_tcb_config *tcb_config;
int irq[3];
struct clk *clk[3];
struct list_head node;
--
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