linux/scripts/kconfig/expr.h

329 lines
9.6 KiB

Kconfig: Introduce the "imply" keyword The "imply" keyword is a weak version of "select" where the target config symbol can still be turned off, avoiding those pitfalls that come with the "select" keyword. This is useful e.g. with multiple drivers that want to indicate their ability to hook into a secondary subsystem while allowing the user to configure that subsystem out without also having to unset these drivers. Currently, the same effect can almost be achieved with: config DRIVER_A tristate config DRIVER_B tristate config DRIVER_C tristate config DRIVER_D tristate [...] config SUBSYSTEM_X tristate default DRIVER_A || DRIVER_B || DRIVER_C || DRIVER_D || [...] This is unwieldy to maintain especially with a large number of drivers. Furthermore, there is no easy way to restrict the choice for SUBSYSTEM_X to y or n, excluding m, when some drivers are built-in. The "select" keyword allows for excluding m, but it excludes n as well. Hence this "imply" keyword. The above becomes: config DRIVER_A tristate imply SUBSYSTEM_X config DRIVER_B tristate imply SUBSYSTEM_X [...] config SUBSYSTEM_X tristate This is much cleaner, and way more flexible than "select". SUBSYSTEM_X can still be configured out, and it can be set as a module when none of the drivers are configured in or all of them are modular. Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Richard Cochran <richardcochran@gmail.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Cc: Paul Bolle <pebolle@tiscali.nl> Cc: linux-kbuild@vger.kernel.org Cc: netdev@vger.kernel.org Cc: Michal Marek <mmarek@suse.com> Cc: Edward Cree <ecree@solarflare.com> Link: http://lkml.kernel.org/r/1478841010-28605-2-git-send-email-nicolas.pitre@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-11 00:10:05 -05:00
Improve kconfig symbol hashing While looking for something else I noticed that the symbol hash function used by kconfig is quite poor. It doesn't use any of the standard hash techniques but simply adds up the string and then uses power of two masking, which is both known to perform poorly. The current x86 kconfig has over 7000 symbols. When I instrumented it showed that the minimum hash chain length was 16 and a significant number of them was over 30. It didn't help that the hash table size was only 256 buckets. This patch increases the hash table size to a larger prime and switches to a FNV32 hash. I played around with a couple of hash functions, but that one seemed to perform best with reasonable hash table sizes. Increasing the hash table size even further didn't seem like a good idea, because there are a couple of global walks which walk the complete hash table. I also moved the unnamed bucket to 0. It's still the longest of all the buckets (44 entries), but hopefully it's not often hit except for the global walk which doesn't care. The result is a much nicer distribution: (first column bucket length, second number of buckets with that length) 1: 3505 2: 1236 3: 294 4: 52 5: 3 47: 1 <--- this is the unnamed symbols bucket There are still some 5+ buckets, but increasing the hash table even more would be likely not worth it. This also cleans up the code slightly by removing hard coded magic numbers. I didn't notice a big performance difference either way on my Nehalem system, but I presume it'll help somewhat on slower systems. Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Michal Marek <mmarek@suse.cz>
2010-01-13 17:02:44 +01:00
kconfig: Fix defconfig when one choice menu selects options that another choice menu depends on The defconfig and Kconfig combination below, which is based on 3.10-rc4 Kconfigs, resulted in several options getting set to "m" instead of "y". defconfig.choice: ---8<--- CONFIG_MODULES=y CONFIG_USB_ZERO=y ---8<--- Kconfig.choice: ---8<--- menuconfig MODULES bool "Enable loadable module support" config CONFIGFS_FS tristate "Userspace-driven configuration filesystem" config OCFS2_FS tristate "OCFS2 file system support" depends on CONFIGFS_FS select CRC32 config USB_LIBCOMPOSITE tristate select CONFIGFS_FS choice tristate "USB Gadget Drivers" default USB_ETH config USB_ZERO tristate "Gadget Zero (DEVELOPMENT)" select USB_LIBCOMPOSITE config USB_ETH tristate "Ethernet Gadget (with CDC Ethernet support)" select USB_LIBCOMPOSITE endchoice config CRC32 tristate "CRC32/CRC32c functions" default y choice prompt "CRC32 implementation" depends on CRC32 default CRC32_SLICEBY8 config CRC32_SLICEBY8 bool "Slice by 8 bytes" endchoice ---8<--- $ scripts/kconfig/conf --defconfig=defconfig.choice Kconfig.choice would result in: .config: ---8<--- CONFIG_MODULES=y CONFIG_CONFIGFS_FS=m CONFIG_USB_LIBCOMPOSITE=m CONFIG_USB_ZERO=m CONFIG_CRC32=y CONFIG_CRC32_SLICEBY8=y ---8<--- when the expected result would be: .config: ---8<--- CONFIG_MODULES=y CONFIG_CONFIGFS_FS=y CONFIG_USB_LIBCOMPOSITE=y CONFIG_USB_ZERO=y CONFIG_CRC32=y CONFIG_CRC32_SLICEBY8=y ---8<--- Signed-off-by: Arve Hjønnevåg <arve@android.com> [yann.morin.1998@free.fr: add the resulting .config to commit log, remove unneeded USB_GADGET from the defconfig] Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
2013-06-06 20:37:00 -07:00
Improve kconfig symbol hashing While looking for something else I noticed that the symbol hash function used by kconfig is quite poor. It doesn't use any of the standard hash techniques but simply adds up the string and then uses power of two masking, which is both known to perform poorly. The current x86 kconfig has over 7000 symbols. When I instrumented it showed that the minimum hash chain length was 16 and a significant number of them was over 30. It didn't help that the hash table size was only 256 buckets. This patch increases the hash table size to a larger prime and switches to a FNV32 hash. I played around with a couple of hash functions, but that one seemed to perform best with reasonable hash table sizes. Increasing the hash table size even further didn't seem like a good idea, because there are a couple of global walks which walk the complete hash table. I also moved the unnamed bucket to 0. It's still the longest of all the buckets (44 entries), but hopefully it's not often hit except for the global walk which doesn't care. The result is a much nicer distribution: (first column bucket length, second number of buckets with that length) 1: 3505 2: 1236 3: 294 4: 52 5: 3 47: 1 <--- this is the unnamed symbols bucket There are still some 5+ buckets, but increasing the hash table even more would be likely not worth it. This also cleans up the code slightly by removing hard coded magic numbers. I didn't notice a big performance difference either way on my Nehalem system, but I presume it'll help somewhat on slower systems. Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Michal Marek <mmarek@suse.cz>
2010-01-13 17:02:44 +01:00
Kconfig: Introduce the "imply" keyword The "imply" keyword is a weak version of "select" where the target config symbol can still be turned off, avoiding those pitfalls that come with the "select" keyword. This is useful e.g. with multiple drivers that want to indicate their ability to hook into a secondary subsystem while allowing the user to configure that subsystem out without also having to unset these drivers. Currently, the same effect can almost be achieved with: config DRIVER_A tristate config DRIVER_B tristate config DRIVER_C tristate config DRIVER_D tristate [...] config SUBSYSTEM_X tristate default DRIVER_A || DRIVER_B || DRIVER_C || DRIVER_D || [...] This is unwieldy to maintain especially with a large number of drivers. Furthermore, there is no easy way to restrict the choice for SUBSYSTEM_X to y or n, excluding m, when some drivers are built-in. The "select" keyword allows for excluding m, but it excludes n as well. Hence this "imply" keyword. The above becomes: config DRIVER_A tristate imply SUBSYSTEM_X config DRIVER_B tristate imply SUBSYSTEM_X [...] config SUBSYSTEM_X tristate This is much cleaner, and way more flexible than "select". SUBSYSTEM_X can still be configured out, and it can be set as a module when none of the drivers are configured in or all of them are modular. Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Richard Cochran <richardcochran@gmail.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Cc: Paul Bolle <pebolle@tiscali.nl> Cc: linux-kbuild@vger.kernel.org Cc: netdev@vger.kernel.org Cc: Michal Marek <mmarek@suse.com> Cc: Edward Cree <ecree@solarflare.com> Link: http://lkml.kernel.org/r/1478841010-28605-2-git-send-email-nicolas.pitre@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-11 00:10:05 -05:00
kconfig: Print reverse dependencies in groups Surprisingly or not, disabling a CONFIG option (which is assumed to be unneeded) may be not so trivial. Especially it is not trivial, when this CONFIG option is selected by a dozen of other configs. Before the moment commit 1ccb27143360 ("kconfig: make "Selected by:" and "Implied by:" readable") popped up in v4.16-rc1, it was an absolute pain to break down the "Selected by" reverse dependency expression in order to identify all those configs which select (IOW *do not allow disabling*) a certain feature (assumed to be not needed). This patch tries to make one step further by putting at users' fingertips the revdep top level OR sub-expressions grouped/clustered by the tristate value they evaluate to. This should allow the users to directly concentrate on and tackle the _active_ reverse dependencies. To give some numbers and quantify the complexity of certain reverse dependencies, assuming commit 617aebe6a97e ("Merge tag 'usercopy-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux"), ARCH=arm64 and vanilla arm64 defconfig, here is the top 10 CONFIG options with the highest amount of top level "||" sub-expressions/tokens that make up the final "Selected by" reverse dependency expression. | Config | All revdep | Active revdep | |-------------------|------------|---------------| | REGMAP_I2C | 212 | 9 | | CRC32 | 167 | 25 | | FW_LOADER | 128 | 5 | | MFD_CORE | 124 | 9 | | FB_CFB_IMAGEBLIT | 114 | 2 | | FB_CFB_COPYAREA | 111 | 2 | | FB_CFB_FILLRECT | 110 | 2 | | SND_PCM | 103 | 2 | | CRYPTO_HASH | 87 | 19 | | WATCHDOG_CORE | 86 | 6 | The story behind the above is that users need to visually review/evaluate 212 expressions which *potentially* select REGMAP_I2C in order to identify the expressions which *actually* select REGMAP_I2C, for a particular ARCH and for a particular defconfig used. To make this experience smoother, change the way reverse dependencies are displayed to the user from [1] to [2]. [1] Old representation of DMA_ENGINE_RAID: Selected by: - AMCC_PPC440SPE_ADMA [=n] && DMADEVICES [=y] && (440SPe || 440SP) - BCM_SBA_RAID [=m] && DMADEVICES [=y] && (ARM64 [=y] || ... - FSL_RAID [=n] && DMADEVICES [=y] && FSL_SOC && ... - INTEL_IOATDMA [=n] && DMADEVICES [=y] && PCI [=y] && X86_64 - MV_XOR [=n] && DMADEVICES [=y] && (PLAT_ORION || ARCH_MVEBU [=y] ... - MV_XOR_V2 [=y] && DMADEVICES [=y] && ARM64 [=y] - XGENE_DMA [=n] && DMADEVICES [=y] && (ARCH_XGENE [=y] || ... - DMATEST [=n] && DMADEVICES [=y] && DMA_ENGINE [=y] [2] New representation of DMA_ENGINE_RAID: Selected by [y]: - MV_XOR_V2 [=y] && DMADEVICES [=y] && ARM64 [=y] Selected by [m]: - BCM_SBA_RAID [=m] && DMADEVICES [=y] && (ARM64 [=y] || ... Selected by [n]: - AMCC_PPC440SPE_ADMA [=n] && DMADEVICES [=y] && (440SPe || ... - FSL_RAID [=n] && DMADEVICES [=y] && FSL_SOC && ... - INTEL_IOATDMA [=n] && DMADEVICES [=y] && PCI [=y] && X86_64 - MV_XOR [=n] && DMADEVICES [=y] && (PLAT_ORION || ARCH_MVEBU [=y] ... - XGENE_DMA [=n] && DMADEVICES [=y] && (ARCH_XGENE [=y] || ... - DMATEST [=n] && DMADEVICES [=y] && DMA_ENGINE [=y] Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com> Reviewed-by: Petr Vorel <pvorel@suse.cz> Reviewed-by: Ulf Magnusson <ulfalizer@gmail.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-02-24 16:24:18 +01:00