diff options
Diffstat (limited to 'drivers/media/usb/uvc/uvc_driver.c')
-rw-r--r-- | drivers/media/usb/uvc/uvc_driver.c | 84 |
1 files changed, 0 insertions, 84 deletions
diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index 9c05776f11d1..0f14dee4b6d7 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -329,90 +329,6 @@ static enum v4l2_ycbcr_encoding uvc_ycbcr_enc(const u8 matrix_coefficients) return V4L2_YCBCR_ENC_DEFAULT; /* Reserved */ } -/* - * Simplify a fraction using a simple continued fraction decomposition. The - * idea here is to convert fractions such as 333333/10000000 to 1/30 using - * 32 bit arithmetic only. The algorithm is not perfect and relies upon two - * arbitrary parameters to remove non-significative terms from the simple - * continued fraction decomposition. Using 8 and 333 for n_terms and threshold - * respectively seems to give nice results. - */ -void uvc_simplify_fraction(u32 *numerator, u32 *denominator, - unsigned int n_terms, unsigned int threshold) -{ - u32 *an; - u32 x, y, r; - unsigned int i, n; - - an = kmalloc_array(n_terms, sizeof(*an), GFP_KERNEL); - if (an == NULL) - return; - - /* - * Convert the fraction to a simple continued fraction. See - * https://en.wikipedia.org/wiki/Continued_fraction - * Stop if the current term is bigger than or equal to the given - * threshold. - */ - x = *numerator; - y = *denominator; - - for (n = 0; n < n_terms && y != 0; ++n) { - an[n] = x / y; - if (an[n] >= threshold) { - if (n < 2) - n++; - break; - } - - r = x - an[n] * y; - x = y; - y = r; - } - - /* Expand the simple continued fraction back to an integer fraction. */ - x = 0; - y = 1; - - for (i = n; i > 0; --i) { - r = y; - y = an[i-1] * y + x; - x = r; - } - - *numerator = y; - *denominator = x; - kfree(an); -} - -/* - * Convert a fraction to a frame interval in 100ns multiples. The idea here is - * to compute numerator / denominator * 10000000 using 32 bit fixed point - * arithmetic only. - */ -u32 uvc_fraction_to_interval(u32 numerator, u32 denominator) -{ - u32 multiplier; - - /* Saturate the result if the operation would overflow. */ - if (denominator == 0 || - numerator/denominator >= ((u32)-1)/10000000) - return (u32)-1; - - /* - * Divide both the denominator and the multiplier by two until - * numerator * multiplier doesn't overflow. If anyone knows a better - * algorithm please let me know. - */ - multiplier = 10000000; - while (numerator > ((u32)-1)/multiplier) { - multiplier /= 2; - denominator /= 2; - } - - return denominator ? numerator * multiplier / denominator : 0; -} - /* ------------------------------------------------------------------------ * Terminal and unit management */ |