Revision 9a765881bf3dcd32847d7108cf48cb04a4ed993f authored by Bjørn Mork on 10 October 2016, 19:12:49 UTC, committed by David S. Miller on 13 October 2016, 14:05:06 UTC
The Quectel EC21 and EC25 need the same "set DTR" request as devices based on the MDM9230 chipset, but has no USB3 support. Our best guess is that the "set DTR" functionality depends on chipset and/or baseband firmware generation. But USB3 is still an optional feature. Since we cannot enable this unconditionally for all older devices, and there doesn't appear to be anything we can use in the USB descriptors to identify these chips, we are forced to use a device specific quirk flag. Reported-and-tested-by: Sebastian Sjoholm <sebastian.sjoholm@gmail.com> Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: David S. Miller <davem@davemloft.net>
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rational.c
/*
* rational fractions
*
* Copyright (C) 2009 emlix GmbH, Oskar Schirmer <oskar@scara.com>
*
* helper functions when coping with rational numbers
*/
#include <linux/rational.h>
#include <linux/compiler.h>
#include <linux/export.h>
/*
* calculate best rational approximation for a given fraction
* taking into account restricted register size, e.g. to find
* appropriate values for a pll with 5 bit denominator and
* 8 bit numerator register fields, trying to set up with a
* frequency ratio of 3.1415, one would say:
*
* rational_best_approximation(31415, 10000,
* (1 << 8) - 1, (1 << 5) - 1, &n, &d);
*
* you may look at given_numerator as a fixed point number,
* with the fractional part size described in given_denominator.
*
* for theoretical background, see:
* http://en.wikipedia.org/wiki/Continued_fraction
*/
void rational_best_approximation(
unsigned long given_numerator, unsigned long given_denominator,
unsigned long max_numerator, unsigned long max_denominator,
unsigned long *best_numerator, unsigned long *best_denominator)
{
unsigned long n, d, n0, d0, n1, d1;
n = given_numerator;
d = given_denominator;
n0 = d1 = 0;
n1 = d0 = 1;
for (;;) {
unsigned long t, a;
if ((n1 > max_numerator) || (d1 > max_denominator)) {
n1 = n0;
d1 = d0;
break;
}
if (d == 0)
break;
t = d;
a = n / d;
d = n % d;
n = t;
t = n0 + a * n1;
n0 = n1;
n1 = t;
t = d0 + a * d1;
d0 = d1;
d1 = t;
}
*best_numerator = n1;
*best_denominator = d1;
}
EXPORT_SYMBOL(rational_best_approximation);
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