Commit d9119b59 authored Feb 24, 2018 by Eugeniu Rosca Committed by Masahiro Yamada Mar 26, 2018

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 1ccb2714 ("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 617aebe6 ("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>

parent 9a47ceec

scripts/kconfig/expr.c

+12 −6

Original line number	Diff line number	Diff line
		@@ -1323,19 +1323,25 @@ void expr_gstr_print(struct expr e, struct gstr gs)
		*/
		static void expr_print_revdep(struct expr *e,
		void (fn)(void , struct symbol , const char ),
		void *data)
		void data, tristate pr_type, const char *title)
		{
		if (e->type == E_OR) {
		expr_print_revdep(e->left.expr, fn, data);
		expr_print_revdep(e->right.expr, fn, data);
		} else {
		expr_print_revdep(e->left.expr, fn, data, pr_type, title);
		expr_print_revdep(e->right.expr, fn, data, pr_type, title);
		} else if (expr_calc_value(e) == pr_type) {
		if (*title) {
		fn(data, NULL, *title);
		*title = NULL;
		}

		fn(data, NULL, " - ");
		expr_print(e, fn, data, E_NONE);
		fn(data, NULL, "\n");
		}
		}

		void expr_gstr_print_revdep(struct expr e, struct gstr gs)
		void expr_gstr_print_revdep(struct expr e, struct gstr gs,
		tristate pr_type, const char *title)
		{
		expr_print_revdep(e, expr_print_gstr_helper, gs);
		expr_print_revdep(e, expr_print_gstr_helper, gs, pr_type, &title);
		}

scripts/kconfig/expr.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -310,7 +310,8 @@ struct expr expr_simplify_unmet_dep(struct expr e1, struct expr *e2);
		void expr_fprint(struct expr e, FILE out);
		struct gstr; /* forward */
		void expr_gstr_print(struct expr e, struct gstr gs);
		void expr_gstr_print_revdep(struct expr e, struct gstr gs);
		void expr_gstr_print_revdep(struct expr e, struct gstr gs,
		tristate pr_type, const char *title);

		static inline int expr_is_yes(struct expr *e)
		{

scripts/kconfig/menu.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -828,16 +828,16 @@ static void get_symbol_str(struct gstr r, struct symbol sym,

		get_symbol_props_str(r, sym, P_SELECT, _(" Selects: "));
		if (sym->rev_dep.expr) {
		str_append(r, _(" Selected by: "));
		str_append(r, "\n");
		expr_gstr_print_revdep(sym->rev_dep.expr, r);
		expr_gstr_print_revdep(sym->rev_dep.expr, r, yes, " Selected by [y]:\n");
		expr_gstr_print_revdep(sym->rev_dep.expr, r, mod, " Selected by [m]:\n");
		expr_gstr_print_revdep(sym->rev_dep.expr, r, no, " Selected by [n]:\n");
		}

		get_symbol_props_str(r, sym, P_IMPLY, _(" Implies: "));
		if (sym->implied.expr) {
		str_append(r, _(" Implied by: "));
		str_append(r, "\n");
		expr_gstr_print_revdep(sym->implied.expr, r);
		expr_gstr_print_revdep(sym->implied.expr, r, yes, " Implied by [y]:\n");
		expr_gstr_print_revdep(sym->implied.expr, r, mod, " Implied by [m]:\n");
		expr_gstr_print_revdep(sym->implied.expr, r, no, " Implied by [n]:\n");
		}

		str_append(r, "\n\n");