Date: Mon, 1 Jul 2013 11:56:25 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Aleksandr Rybalko <ray@FreeBSD.org> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r252425 - head/sys/arm/arm Message-ID: <20130701113808.F894@besplex.bde.org> In-Reply-To: <201306301952.r5UJqfwf010873@svn.freebsd.org> References: <201306301952.r5UJqfwf010873@svn.freebsd.org>
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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@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.
> ...
> +#define GENERIC_TIMER_CNTPSIRQ 29
Here the interesting part CNTPSIRQ is fairly abbreviated, but its prefix
is not.
>
> 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.
> @@ -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:
- 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
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