Use the ISA bus driver for PC/104 and ISA devices

Two new ISA bus driver macros are introduced in this patchset:
module_isa_driver and max_num_isa_dev.

The module_isa_driver macro is a helper macro for ISA drivers which do not do anything special in module init/exit. This macro is modelled after the module_pci_driver macro and eliminates a lot of module init/exit boilerplate code.

The max_num_isa_dev macro is used to determine the maximum possible number of ISA devices which may be registered in the I/O port address space given the address extent of the ISA devices. This macro is useful for computing the maximum number of elements necessary to hold the base addresses and interrupt line numbers of ISA devices for the respective ISA driver.

Lacking other documentation, I often found myself repeatedly returning to the commit message of the initial commit for drivers/base/isa.c authored by Rene Herman. A verbatim copy of this commit message has been added to Documentation/isa.txt, along with descriptions for the module_isa driver and max_num_isa_dev macros, for posterity.

The Apex Embedded Systems STX104 DAC driver expects to run on an x86 platform. This patchset adds an explicit X86 dependency for the Apex Embedded Systems STX104 DAC driver Kconfig option to prevent building the driver for nonsupported architectures.

Similarly, many PC/104 and ISA devices may also be used on both 32-bit and 64-bit X86 systems. The platform driver had been used to enable support for these devices on 64-bit X86 systems. With the removal of the X86_32 dependency of the ISA Kconfig configuration option, the respective drivers for these devices may now utilize the ISA bus driver without restricting support to only 32-bit X86 systems; the following drivers now utilize the ISA bus driver over the platform driver:

* WinSystems EBC-C384 watchdog timer
* ACCES 104-DIO-48E GPIO driver
* ACCES 104-IDI-48 GPIO driver
* ACCES 104-IDIO-16 GPIO driver
* WinSystems WS16C48 GPIO driver

With the utilization of the ISA bus driver, the GPIO drivers in this patchset may now support multiple devices for each of their respective ISA drivers. A naming convention for module array parameters has been set based on the Apex Embedded Systems STX104 DAC driver.

The "base" array module parameter sets the I/O port base address of each device. The "irq" array module parameter sets the interrupt line number of each device. Each element of the "base" array corresponds to a discrete device; each element of the "irq" array corresponds to the respective device addressed in the respective "base" array element.

Changes in v2:
- Added William Breathitt Gray as maintainer of the relevant ISA bus driver files
- STX104 DAC driver Kconfig option patch now simply adds explicit X86 Kconfig option dependency
- ISA_BUS Kconfig option dependency has been replaced with ISA Kconfig option dependency

William Breathitt Gray (10):
isa: Implement the module_isa_driver macro
isa: Implement the max_num_isa_dev macro
Documentation: Add ISA bus driver documentation
iio: stx104: Add X86 dependency to STX104 Kconfig option
iio: stx104: Utilize the module_isa_driver and max_num_isa_dev macros
watchdog: ebc-c384_wdt: Utilize the ISA bus driver
gpio: 104-dio-48e: Utilize the ISA bus driver
gpio: 104-idi-48: Utilize the ISA bus driver
gpio: 104-idio-16: Utilize the ISA bus driver
gpio: ws16c48: Utilize the ISA bus driver

 Documentation/isa.txt           | 121 ++++++++++++++++++++++++++++++++++++++++
 MAINTAINERS                     |   7 +++
 drivers/gpio/Kconfig            |  38 +++++++------
 drivers/gpio/gpio-104-dio-48e.c | 106 +++++++++++++----------------------
 drivers/gpio/gpio-104-idi-48.c  |  86 ++++++++++------------------
 drivers/gpio/gpio-104-idio-16.c |  85 ++++++++++------------------
 drivers/gpio/gpio-ws16c48.c     |  88 ++++++++++-------------------
 drivers/iio/dac/Kconfig         |   2 +-
 drivers/iio/dac/stx104.c        |  24 +-------
 drivers/watchdog/Kconfig        |   2 +-
 drivers/watchdog/ebc-c384_wdt.c |  43 ++++----------
 include/linux/isa.h             |  32 +++++++++++
 12 files changed, 319 insertions(+), 315 deletions(-)
 create mode 100644 Documentation/isa.txt

2.7.3