Hello Petr,
On Sun, Feb 04, 2018 at 04:50:54PM +0100, Petr Vorel wrote:
> Hi Eugeniu,
>
> > From: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
>
> > Commit 1ccb27143360 ("kconfig: make "Selected by:" and "Implied by:"
> > readable") made an incredible improvement in how reverse dependencies
> > are perceived by the user, by breaking down the single (often
> > interminable) expression string into small readable chunks.
>
> > Even so, what happens in practice when reading the reverse
> > dependencies is that 80-90% of the OR sub-expressions simply don't
> > matter, since they evaluate to [=n].
>
> > 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 30 of CONFIG options with
> > the highest amount of OR sub-expressions that make up the final
> > "{Selected,Implied} by" reverse dependency expression.
>
> > | Config | Revdep all | Revdep ![=n] |
> > |-------------------------------|------------|--------------|
> > | 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 |
> > | IRQ_DOMAIN | 75 | 19 |
> > | SERIAL_CORE | 75 | 9 |
> > | PHYLIB | 74 | 16 |
> > | REGMAP_MMIO | 72 | 15 |
> > | GENERIC_PHY | 67 | 20 |
> > | DMA_ENGINE | 66 | 11 |
> > | SERIAL_CORE_CONSOLE | 64 | 9 |
> > | CRYPTO_BLKCIPHER | 64 | 13 |
> > | PINMUX | 60 | 17 |
> > | CRYPTO | 59 | 10 |
> > | MII | 58 | 8 |
> > | GPIOLIB_IRQCHIP | 58 | 9 |
> > | MFD_SYSCON | 58 | 15 |
> > | VIDEOBUF2_DMA_CONTIG | 46 | 4 |
> > | REGMAP_IRQ | 45 | 6 |
> > | REGMAP_SPI | 44 | 2 |
> > | CLKSRC_MMIO | 42 | 5 |
> > | SND_SOC_GENERIC_DMAENGINE_PCM | 41 | 3 |
> > | CRYPTO_SHA1 | 37 | 2 |
> > | REGMAP | 36 | 4 |
>
> > The story behind the above is that we still 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.
>
> > This patch attempts to bring at user's fingertips those reverse
> > dependencies that actually participate in selection of given symbol
> > filtering out the rest of them.
>
> > Signed-off-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
> > ---
> > scripts/kconfig/expr.c | 24 +++++++++++++++++-------
> > 1 file changed, 17 insertions(+), 7 deletions(-)
>
> > diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
> > index 2ba332b3fed7..147b2d8a8f3e 100644
> > --- a/scripts/kconfig/expr.c
> > +++ b/scripts/kconfig/expr.c
> > @@ -1234,14 +1234,24 @@ static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, con
> > fn(data, e->right.sym, e->right.sym->name);
> > break;
> > case E_OR:
> > - if (revdep && e->left.expr->type != E_OR)
> > - fn(data, NULL, "\n - ");
> > - __expr_print(e->left.expr, fn, data, E_OR, revdep);
> > - if (revdep)
> > - fn(data, NULL, "\n - ");
> > - else
> > + if (revdep) {
> > + struct expr *left = e->left.expr;
> > + struct expr *right = e->right.expr;
> > +
> > + if (expr_calc_value(left) != no) {
> > + if (left->type != E_OR)
> > + fn(data, NULL, "\n - ");
> > + __expr_print(left, fn, data, E_OR, revdep);
> > + }
> > + if (expr_calc_value(right) != no) {
> > + fn(data, NULL, "\n - ");
> > + __expr_print(right, fn, data, E_OR, revdep);
> > + }
> > + } else {
> > + __expr_print(e->left.expr, fn, data, E_OR, revdep);
> > fn(data, NULL, " || ");
> > - __expr_print(e->right.expr, fn, data, E_OR, revdep);
> > + __expr_print(e->right.expr, fn, data, E_OR, revdep);
> > + }
> > break;
> > case E_AND:
> > expr_print(e->left.expr, fn, data, E_AND);
>
> Thanks for trying to improve my change.
>
> Applying your patch, running
> $ ARCH=arm64 make defconfig && ARCH=arm64 make menuconfig
> and searching for USB prints "Selected by:" with nothing actually selected.
I think the behavior is correct. All expressions that select USB
translate/evaluate to =n. CONFIG_USB is enabled in the arm64 defconfig.
> Kind regards,
> Petr
Thanks,
Eugeniu.
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