math: rational: add missing MODULE_DESCRIPTION() macro

With ARCH=sh, make allmodconfig && make W=1 C=1 reports: WARNING: modpost:
missing MODULE_DESCRIPTION() in lib/math/rational.o

Add the missing

math: rational: add missing MODULE_DESCRIPTION() macro

With ARCH=sh, make allmodconfig && make W=1 C=1 reports: WARNING: modpost:
missing MODULE_DESCRIPTION() in lib/math/rational.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jeff Johnson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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math: make RATIONAL tristate

Patch series "math: RATIONAL and RATIONAL_KUNIT_TEST improvements".

This series makes the RATIONAL symbol tristate, so it is not forced
builtin if all users are modular

math: make RATIONAL tristate

Patch series "math: RATIONAL and RATIONAL_KUNIT_TEST improvements".

This series makes the RATIONAL symbol tristate, so it is not forced
builtin if all users are modular, and makes the RATIONAL_KUNIT_TEST depend
on RATIONAL, to avoid enabling RATIONAL if there are no real users.

This patch (of 2):

All but one symbols that select RATIONAL are tristate, but RATIONAL itself
is bool. Change it to tristate, so the rational fractions support code
can be modular if no builtin code relies on it.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Trent Piepho <[email protected]>
Cc: Colin Ian King <[email protected]>
Cc: Brendan Higgins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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lib/math/rational.c: fix divide by zero

If the input is out of the range of the allowed values, either larger than
the largest value or closer to zero than the smallest non-zero allowed
value, then

lib/math/rational.c: fix divide by zero

If the input is out of the range of the allowed values, either larger than
the largest value or closer to zero than the smallest non-zero allowed
value, then a division by zero would occur.

In the case of input too large, the division by zero will occur on the
first iteration. The best result (largest allowed value) will be found by
always choosing the semi-convergent and excluding the denominator based
limit when finding it.

In the case of the input too small, the division by zero will occur on the
second iteration. The numerator based semi-convergent should not be
calculated to avoid the division by zero. But the semi-convergent vs
previous convergent test is still needed, which effectively chooses
between 0 (the previous convergent) vs the smallest allowed fraction (best
semi-convergent) as the result.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 323dd2c3ed0 ("lib/math/rational.c: fix possible incorrect result from rational fractions helper")
Signed-off-by: Trent Piepho <[email protected]>
Reported-by: Yiyuan Guo <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Oskar Schirmer <[email protected]>
Cc: Daniel Latypov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kernel.h: split out min()/max() et al. helpers

kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out min()/max()
et al

kernel.h: split out min()/max() et al. helpers

kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out min()/max()
et al. helpers.

At the same time convert users in header and lib folder to use new header.
Though for time being include new header back to kernel.h to avoid
twisted indirected includes for other existing users.

Signed-off-by: Andy Shevchenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

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lib/: replace HTTP links with HTTPS ones

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Signed-off-by: Alexander A. Klimo

lib/: replace HTTP links with HTTPS ones

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Signed-off-by: Alexander A. Klimov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Coly Li <[email protected]> [crc64.c]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

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lib/math/rational.c: fix possible incorrect result from rational fractions helper

In some cases the previous algorithm would not return the closest
approximation. This would happen when a semi-conv

lib/math/rational.c: fix possible incorrect result from rational fractions helper

In some cases the previous algorithm would not return the closest
approximation. This would happen when a semi-convergent was the
closest, as the previous algorithm would only consider convergents.

As an example, consider an initial value of 5/4, and trying to find the
closest approximation with a maximum of 4 for numerator and denominator.
The previous algorithm would return 1/1 as the closest approximation,
while this version will return the correct answer of 4/3.

To do this, the main loop performs effectively the same operations as it
did before. It must now keep track of the last three approximations,
n2/d2 .. n0/d0, while before it only needed the last two.

If an exact answer is not found, the algorithm will now calculate the
best semi-convergent term, t, which is a single expression with two
divisions:

min((max_numerator - n0) / n1, (max_denominator - d0) / d1)

This will be used if it is better than previous convergent. The test
for this is generally a simple comparison, 2*t > a. But in an edge
case, where the convergent's final term is even and the best allowable
semi-convergent has a final term of exactly half the convergent's final
term, the more complex comparison (d0*dp > d1*d) is used.

I also wrote some comments explaining the code. While one still needs
to look up the math elsewhere, they should help a lot to follow how the
code relates to that math.

This routine is used in two places in the video4linux code, but in those
cases it is only used to reduce a fraction to lowest terms, which the
existing code will do correctly. This could be done more efficiently
with a different library routine but it would still be the Euclidean
alogrithm at its heart. So no change.

The remain users are places where a fractional PLL divider is
programmed. What would happen is something asked for a clock of X MHz
but instead gets Y MHz, where Y is close to X but not exactly due to the
hardware limitations. After this change they might, in some cases, get
Y' MHz, where Y' is a little closer to X then Y was.

Users like this are: Three UARTs, in 8250_mid, 8250_lpss, and imx. One
GPU in vp4_hdmi. And three clock drivers, clk-cdce706, clk-si5351, and
clk-fractional-divider. The last is a generic clock driver and so would
have more users referenced via device tree entries.

I think there's a bug in that one, it's limiting an N bit field that is
offset-by-1 to the range 0 .. (1<<N)-2, when it should be (1<<N)-1 as
the upper limit.

I have an IMX system, one of the UARTs using this, so I can provide a
real example. If I request a custom baud rate of 1499978, the driver
will program the PLL to produce a baud rate of 1500000. After this
change, the fractional divider in the UART is programmed to a ratio of
65535/65536, which produces a baud rate of 1499977.0625. Closer to the
requested value.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Trent Piepho <[email protected]>
Cc: Oskar Schirmer <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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lib: Move mathematic helpers to separate folder

For better maintenance and expansion move the mathematic helpers to the
separate folder.

No functional change intended.

Note, the int_sqrt() is not

lib: Move mathematic helpers to separate folder

For better maintenance and expansion move the mathematic helpers to the
separate folder.

No functional change intended.

Note, the int_sqrt() is not used as a part of lib, so, moved to regular
obj.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andy Shevchenko <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Lee Jones <[email protected]>
Cc: Daniel Thompson <[email protected]>
Cc: Ray Jui <[email protected]>
[[email protected]: fix broken doc references for div64.c and gcd.c]
Link: http://lkml.kernel.org/r/734f49bae5d4052b3c25691dfefad59bea2e5843.1555580999.git.mchehab+samsung@kernel.org
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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