On 08/01/2012 02:46 PM, Steven Rostedt wrote: > On Wed, 2012-08-01 at 12:56 +0200, Lars-Peter Clausen wrote: > >> You could do that by using a construct like below, but well... >> >> config HAS_PWM >> bool >> >> config PWM >> bool "PWM >> depends on HAS_PWM >> >> config PWM_CAN_BUILD_DRIVER_X >> defbool I2C >> select HAS_PWM >> >> config PWM_DRIVER_X >> tristate "PWM chip X support" >> depends on PWM && PWM_CAN_BUILD_DRIVER_X >> >> config PWM_CAN_BUILD_DRIVER_Y >> defbool ARCH_Y >> select HAS_PWM >> >> config PWM_DRIVER_Y >> tristate "PWM chip Y support" >> depends on PWM && PWM_CAN_BUILD_DRIVER_Y > > What selects the 'PWM_CAN_BUILD_DRIVER_FOO'? >
Its def_bool statement, which lists the prerequisites to build the driver. E.g. for a I2C PWM expander I2S support, for a on-SoC PWM core support for the SoC family, etc.. So it will be true if the driver can actually be built and false otherwise. If one of the PWM_CAN_BUILD_DRIVER_FOO symbols is true also HAS_PWM will be true and PWM becomes selectable. But it seems to be a bid tedious to have these extra lines for each driver and I guess it is not a PWM subsystem specific issue. There are other subsystems where this probably applies as well, e.g. the MFD subsystem. Also such a solution would rule out out-of-tree PWM driver modules, since it is not possible to get CONFIG_PWM selected. - Lars -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
