svn commit: r252425 - head/sys/arm/arm

[Aleksandr Rybalko]

On Mon, 1 Jul 2013 11:56:25 +1000 (EST)
Bruce Evans <brde at optusnet.com.au> wrote:

> On Sun, 30 Jun 2013, Aleksandr Rybalko wrote:
> 
> > Log:
> >  Decrypt magic numbers - define names for fields of Generic Timer's CNTKCTL reg.
> >
> >  Submitted by:	Ruslan Bukin <br at bsdpad.com>
> >
> > Modified:
> >  head/sys/arm/arm/generic_timer.c
> >
> > Modified: head/sys/arm/arm/generic_timer.c
> > ==============================================================================
> > --- head/sys/arm/arm/generic_timer.c	Sun Jun 30 19:36:17 2013	(r252424)
> > +++ head/sys/arm/arm/generic_timer.c	Sun Jun 30 19:52:41 2013	(r252425)
> > @@ -66,7 +66,22 @@ __FBSDID("$FreeBSD$");
> > #define	GENERIC_TIMER_REG_CTRL		0
> > #define	GENERIC_TIMER_REG_TVAL		1
> >
> > -#define	CNTPSIRQ	29
> > +#define	GENERIC_TIMER_CNTKCTL_PL0PTEN	(1 << 9) /* Physical timer registers
> > +						    access from PL0 */
> > +#define	GENERIC_TIMER_CNTKCTL_PL0VTEN	(1 << 8) /* Virtual timer registers
> 
> With names like these, the magic numbers are better.  The prefix name
> GENERIC_TIMER is especially bad.  GT would be good.

Changed in r252780.

> 
> > ...
> > +#define	GENERIC_TIMER_CNTPSIRQ	29
> 
> Here the interesting part CNTPSIRQ is fairly abbreviated, but its prefix
> is not.

GENERIC_TIMER was original prefix before timer access bits was added,
but CNTPSIRQ is original name from documentation. Name was preserved to
avoid confusion.

> 
> >
> > struct arm_tmr_softc {
> > 	struct resource		*irq_res;
> > @@ -167,7 +182,11 @@ disable_user_access(void)
> > 	uint32_t cntkctl;
> >
> > 	__asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
> > -	cntkctl &= ~((3 << 8) | (7 << 0));
> > +	cntkctl &= ~(GENERIC_TIMER_CNTKCTL_PL0PTEN |
> > +		GENERIC_TIMER_CNTKCTL_PL0VTEN |
> > +		GENERIC_TIMER_CNTKCTL_EVNTEN |
> > +		GENERIC_TIMER_CNTKCTL_PL0VCTEN |
> > +		GENERIC_TIMER_CNTKCTL_PL0PCTEN);
> > 	__asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
> > 	isb();
> > }
> 
> Using these verbose names takes about 15 times as much code as
> before (the statement is only 5 times longer, but the definitions
> macros are about 10 times longer), and looks like even more becayse
> the statement is misformatted with non-KNF indentation which then
> requires extra line spitting with only 1 name per line.

Now a lot of bytes saved! :)

> 
> > @@ -270,7 +289,8 @@ arm_tmr_attach(device_t dev)
> >
> > 	rid = 0;
> > 	sc->irq_res = bus_alloc_resource(dev, SYS_RES_IRQ, &rid,
> > -	    CNTPSIRQ, CNTPSIRQ, 1, RF_SHAREABLE | RF_ACTIVE);
> > +	    GENERIC_TIMER_CNTPSIRQ, GENERIC_TIMER_CNTPSIRQ,
> > +	    1, RF_SHAREABLE | RF_ACTIVE);
> >
> > 	arm_tmr_sc = sc;
> 
> For full uglyness, expand all the prefixes and names:

I will! :-D

> - SYS -> SYSTEM
> - RES -> RESOURCE
> - IRQ -> INTERRUPT_REQUEST_NUMBER
> - SYS_RES_IRQ -> SYSTEM_RESOURCE_INTERRUPT_REQUEST_NUMBER
> - RF -> RESOURCE_FLAG
> - RF_SHAREABLE_RESOURCE_FLAG_SHAREABLE 
> - RF_ACTIVE -> RESOURCE_FLAG_ACTIVE
> - CNTPSIRQ -> COUNT_PRIVATELY_SOURCED_INTERRUPT_REQUEST_NUMBER
>    (just guessing what PS means):
> 
>  	sc->irq_res = bus_alloc_resource(dev, SYS_RES_INTERRUPT_REQUEST_NUMBER,
>  	    &rid,
>  	    GENERIC_TIMER_COUNT_PRIVATELY_SOURCED_INTERRUPT_REQUEST_NUMBER,
>  	    GENERIC_TIMER_COUNT_PRIVATELY_SOURCED_INTERRUPT_REQUEST_NUMBER,
>  	    1, RESOURCE_FLAG_SHAREABLE | RESOURCE_FLAG_ACTIVE);
> 
> Next, use non-KNF indentation:
> 
>  	sc->irq_res = bus_alloc_resource(dev, SYS_RES_INTERRUPT_REQUEST_NUMBER,
>  		&rid,
>  		GENERIC_TIMER_COUNT_PRIVATELY_SOURCED_INTERRUPT_REQUEST_NUMBER,
>  		GENERIC_TIMER_COUNT_PRIVATELY_SOURCED_INTERRUPT_REQUEST_NUMBER,
>  		1, RESOURCE_FLAG_SHAREABLE | RESOURCE_FLAG_ACTIVE);
> 
> The names aren't even 80 characters long, so they actually fit on 1 line.
> 
> Bruce

Thanks Bruce!

"Long words only upset me." (c) Vinny-Pooh (USSR version) :-D

-- 
Aleksandr Rybalko <ray at freebsd.org>