2018-02-25 0:24 GMT+09:00 Eugeniu Rosca <roscaeugeniu@xxxxxxxxx>:
> From: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
> ---
> v4->v5:
> * 99% based on Masahiro's https://patchwork.kernel.org/patch/10231295/
> * Requires Masahiro's https://patchwork.kernel.org/patch/10229545/
> * Fixes review findings from Petr Vorel:
> * Adds a colon symbol to the end of every "Selected by [y|m|n]"
> * Fixes copy-paste error (s/sym->rev_dep.expr/sym->implied.expr/)
> leading to segfault when searching for PTP_1588_CLOCK in menuconfig.
> * Ignores checkpatch findings:
> * "WARNING: line over 80 characters", for the same of readability.
> * "ERROR: Please use git commit description style", which seems to
> be a checkpatch issue.
>
> v3->v4 (fixed review findings from Ulf):
> * Remove redundant default cases in switch constructs.
> * Remove gettext _() tokens in str_append() calls.
> * Aggregate code repetitions in expr_print_revdep().
>
> v2->v3:
> * Switch from reverse dependencies prefixed by their tristate value to
> reverse dependencies grouped by the tristate value they evaluate to.
> * Skip printing "{Selected,Implied} by [y|m|n]:" if there are no top
> level OR tokens/sub-expressions that evaluate to y|m|n (suggested
> by Petr).
> * Use [1] as template for updating the interface/prototype of
> __expr_print() (suggested by Ulf).
>
> v1->v2:
> * Don't skip the =n reverse dependency OR tokens, since some users might
> still need this information (suggested by Ulf).
> * Instead of using "Selected by" for active tokens only, use it for all
> OR tokens, but specify the tristate value of each token as prefix
> (suggested by Masahiro).
Applied with
Reviewed-by: Petr Vorel <pvorel@xxxxxxx>
Reviewed-by: Ulf Magnusson <ulfalizer@xxxxxxxxx>
Thanks!
--
Best Regards
Masahiro Yamada
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