isa: Allow ISA-style drivers on modern systems

Several modern devices, such as PC/104 cards, are expected to run on
modern systems via an ISA bus interface. Since ISA is a legacy interface
for most modern architectures, ISA support should remain disabled in
general. Support for ISA-style drivers should be enabled on a per driver
basis.

To allow ISA-style drivers on modern systems, this patch introduces the
ISA_BUS_API and ISA_BUS Kconfig options. The ISA bus driver will now
build conditionally on the ISA_BUS_API Kconfig option, which defaults to
the legacy ISA Kconfig option. The ISA_BUS Kconfig option allows the
ISA_BUS_API Kconfig option to be selected on architectures which do not
enable ISA (e.g. X86_64).

The ISA_BUS Kconfig option is currently only implemented for X86
architectures. Other architectures may have their own ISA_BUS Kconfig
options added as required.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 14 insertions, 2 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index d794384a0404..e9734796531f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -606,6 +606,9 @@ config HAVE_ARCH_HASH
           file which provides platform-specific implementations of some
           functions in <linux/hash.h> or fs/namei.c.
 
+config ISA_BUS_API
+        def_bool ISA
+
 #
 # ABI hall of shame
 #
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0a7b885964ba..d9a94da0c29f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2439,6 +2439,15 @@ config PCI_CNB20LE_QUIRK
 
 source "drivers/pci/Kconfig"
 
+config ISA_BUS
+        bool "ISA-style bus support on modern systems" if EXPERT
+        select ISA_BUS_API
+        help
+          Enables ISA-style drivers on modern systems. This is necessary to
+          support PC/104 devices on X86_64 platforms.
+
+          If unsure, say N.
+
 # x86_64 have no ISA slots, but can have ISA-style DMA.
 config ISA_DMA_API
         bool "ISA-style DMA support" if (X86_64 && EXPERT)
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 6b2a84e7f2be..2609ba20b396 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -10,7 +10,7 @@ obj-$(CONFIG_DMA_CMA) += dma-contiguous.o
 obj-y                   += power/
 obj-$(CONFIG_HAS_DMA)   += dma-mapping.o
 obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
-obj-$(CONFIG_ISA)       += isa.o
+obj-$(CONFIG_ISA_BUS_API)       += isa.o
 obj-$(CONFIG_FW_LOADER) += firmware_class.o
 obj-$(CONFIG_NUMA)      += node.o
 obj-$(CONFIG_MEMORY_HOTPLUG_SPARSE) += memory.o
diff --git a/include/linux/isa.h b/include/linux/isa.h
index 5ab85281230b..384ab9b7d79a 100644
--- a/include/linux/isa.h
+++ b/include/linux/isa.h
@@ -22,7 +22,7 @@ struct isa_driver {
 
 #define to_isa_driver(x) container_of((x), struct isa_driver, driver)
 
-#ifdef CONFIG_ISA
+#ifdef CONFIG_ISA_BUS_API
 int isa_register_driver(struct isa_driver *, unsigned int);
 void isa_unregister_driver(struct isa_driver *);
 #else