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 X86 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).

For now, the ISA_BUS Kconfig option is only be available on X86
architectures. Support for other architectures may be added as required.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: William Breathitt Gray <redacted>
---
 arch/x86/Kconfig      | 13 +++++++++++++
 drivers/base/Makefile |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0a7b885..a41c0b8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -2439,6 +2439,19 @@ config PCI_CNB20LE_QUIRK
 
 source "drivers/pci/Kconfig"
 
+config ISA_BUS_API
+	def_bool ISA
+
+config ISA_BUS
+	bool "ISA-style bus support on modern systems" if (X86 && EXPERT)
+	default y

+	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 Y.
+
 # 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 6b2a84e..2609ba2 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