x86/irq: Standardize on CONFIG_SPARSE_IRQ=y

Sparseirq got introduced in v2.6.28 and Thomas did a huge cleanup
around v2.6.38 that eliminated basically all disadvantages
of it.

So we can remove non-sparseirq support now and simplify
our IRQ degrees of freedom a bit.

Suggested-and-acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/4E95E21D.6090200@oracle.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -64,6 +64,7 @@ config X86
 	select HAVE_TEXT_POKE_SMP
 	select HAVE_GENERIC_HARDIRQS
 	select HAVE_SPARSE_IRQ
+	select SPARSE_IRQ
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_IRQ_PROBE
 	select GENERIC_PENDING_IRQ if SMP

arch/x86/include/asm/irq_vectors.h

@@ -160,19 +160,11 @@ static inline int invalid_vm86_irq(int irq)
 #define IO_APIC_VECTOR_LIMIT		( 32 * MAX_IO_APICS )
 
 #ifdef CONFIG_X86_IO_APIC
-# ifdef CONFIG_SPARSE_IRQ
-#  define CPU_VECTOR_LIMIT		(64 * NR_CPUS)
-#  define NR_IRQS					\
+# define CPU_VECTOR_LIMIT		(64 * NR_CPUS)
+# define NR_IRQS					\
 	(CPU_VECTOR_LIMIT > IO_APIC_VECTOR_LIMIT ?	\
 		(NR_VECTORS + CPU_VECTOR_LIMIT)  :	\
 		(NR_VECTORS + IO_APIC_VECTOR_LIMIT))
-# else
-#  define CPU_VECTOR_LIMIT		(32 * NR_CPUS)
-#  define NR_IRQS					\
-	(CPU_VECTOR_LIMIT < IO_APIC_VECTOR_LIMIT ?	\
-		(NR_VECTORS + CPU_VECTOR_LIMIT)  :	\
-		(NR_VECTORS + IO_APIC_VECTOR_LIMIT))
-# endif
 #else /* !CONFIG_X86_IO_APIC: */
 # define NR_IRQS			NR_IRQS_LEGACY
 #endif

arch/x86/kernel/apic/io_apic.c

@@ -186,11 +186,7 @@ static struct irq_pin_list *alloc_irq_pin_list(int node)
 
 
 /* irq_cfg is indexed by the sum of all RTEs in all I/O APICs. */
-#ifdef CONFIG_SPARSE_IRQ
 static struct irq_cfg irq_cfgx[NR_IRQS_LEGACY];
-#else
-static struct irq_cfg irq_cfgx[NR_IRQS];
-#endif
 
 int __init arch_early_irq_init(void)
 {
@@ -234,7 +230,6 @@ int __init arch_early_irq_init(void)
 	return 0;
 }
 
-#ifdef CONFIG_SPARSE_IRQ
 static struct irq_cfg *irq_cfg(unsigned int irq)
 {
 	return irq_get_chip_data(irq);
@@ -269,22 +264,6 @@ static void free_irq_cfg(unsigned int at, struct irq_cfg *cfg)
 	kfree(cfg);
 }
 
-#else
-
-struct irq_cfg *irq_cfg(unsigned int irq)
-{
-	return irq < nr_irqs ? irq_cfgx + irq : NULL;
-}
-
-static struct irq_cfg *alloc_irq_cfg(unsigned int irq, int node)
-{
-	return irq_cfgx + irq;
-}
-
-static inline void free_irq_cfg(unsigned int at, struct irq_cfg *cfg) { }
-
-#endif
-
 static struct irq_cfg *alloc_irq_and_cfg_at(unsigned int at, int node)
 {
 	int res = irq_alloc_desc_at(at, node);
@@ -3644,7 +3623,6 @@ int get_nr_irqs_gsi(void)
 	return nr_irqs_gsi;
 }
 
-#ifdef CONFIG_SPARSE_IRQ
 int __init arch_probe_nr_irqs(void)
 {
 	int nr;
@@ -3664,7 +3642,6 @@ int __init arch_probe_nr_irqs(void)
 
 	return NR_IRQS_LEGACY;
 }
-#endif
 
 int io_apic_set_pci_routing(struct device *dev, int irq,
 			    struct io_apic_irq_attr *irq_attr)