On Wed, Apr 04, 2018 at 01:19:29PM +0200, Linus Walleij wrote: >- There is a series of ISA_BUS_API changes that ended up > getting queued in my tree. Most of them have proper ACKs > and they have been tested throughly in linux-next. > These patches finally split ISA_BUS and ISA_BUS_API > apart as I understand it, as there are devices using > port-mapped I/O but not strictly speaking using any ISA > bus. So the ISA_BUS and the ISA_BUS_API are two > things. The most notable effect of ISA_BUS_API is that > it compiles drivers/base/isa.c so that we get device driver > core infrastructure for these devices. The ISA bus was merged > in 2006 (a5117ba7da37) and was used for sound cards and > watchdog, but only recently William started > to use it for his industrial data acquisition cards and he's found > a bit of problems that are now (hopefully) finally fixed up. > Any questions: William Breathitt Gray is on the CC for this > pull request to answer them.
Some background on the impetus and rationale of the ISA_BUS_API Kconfig changes: During submission of the Winbond GPIO driver (a0d65009411c), an attempt to select ISA_BUS_API revealed a recursive dependency bug: https://lkml.org/lkml/2017/12/26/235 The recursive dependency could be avoided if ISA_BUS_API was selected by drivers where needed rather than depended on. A select semantic makes sense as well for these drivers because ISA_BUS_API is simply used to compile the drivers/base/isa.c file, which is just a thin wrapper to allow these ISA-style I/O port drivers to fit the device driver model. ISA_BUS_API is decoupled from the ISA_BUS so that it can be selected independent of the legacy ISA_BUS drivers, which do not necessary make use of drivers/base/isa.c functionality. Thus there is a clean separation between the modern drivers for ISA-style devices which select ISA_BUS_API, and the legacy drivers for true ISA cards which utilize the legacy ISA_BUS Kconfig option. The reason these changes are coming in through the GPIO tree is to avoid a similar recursive dependency error if the STX104 IIO driver attempts to select ISA_BUS_API separate from the other patches (due to its GPIOLIB selection): https://lkml.org/lkml/2017/12/29/384 These updates missed the last merge window, so the Winbond GPIO driver was merged in at that time with a "depends on ISA_BUS_API" line patch to pacify the recursive dependency error. Now that these updates were picked up in the GPIO tree, the revert patch was merged to revert the "depends on ISA_BUS_API" line to the originally intended "select ISA_BUS_API" line. Finally, an explicit EXPERT dependency is added to the PC104 Kconfig option to keep the PC/104 drivers masked as they have been -- the PC/104 interface is somewhat niche and unlikely to be a concern for regular users, so let's keep it tucked away. William Breathitt Gray