From patchwork Sun Dec 5 22:57:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Grzeschik X-Patchwork-Id: 521257 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A213FC4332F for ; Sun, 5 Dec 2021 22:58:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240474AbhLEXBm (ORCPT ); Sun, 5 Dec 2021 18:01:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33202 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238190AbhLEXBi (ORCPT ); Sun, 5 Dec 2021 18:01:38 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D336DC0613F8 for ; Sun, 5 Dec 2021 14:58:10 -0800 (PST) Received: from dude.hi.pengutronix.de ([2001:67c:670:100:1d::7]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mu0SP-0006eI-1K; Sun, 05 Dec 2021 23:58:09 +0100 Received: from mgr by dude.hi.pengutronix.de with local (Exim 4.94.2) (envelope-from ) id 1mu0SO-00182G-7Z; Sun, 05 Dec 2021 23:58:08 +0100 From: Michael Grzeschik To: linux-usb@vger.kernel.org Cc: balbi@kernel.org, laurent.pinchart@ideasonboard.com, paul.elder@ideasonboard.com, kernel@pengutronix.de Subject: [PATCH v4 1/7] media: v4l: move helper functions for fractions from uvc to v4l2-common Date: Sun, 5 Dec 2021 23:57:57 +0100 Message-Id: <20211205225803.268492-2-m.grzeschik@pengutronix.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211205225803.268492-1-m.grzeschik@pengutronix.de> References: <20211205225803.268492-1-m.grzeschik@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::7 X-SA-Exim-Mail-From: mgr@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-usb@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org The functions uvc_simplify_fraction and uvc_fraction_to_interval are generic helpers which are also useful for other v4l2 drivers. This patch moves them to v4l2-common. Signed-off-by: Michael Grzeschik --- v1 -> v2: - v2 -> v3: - v3 -> v4: - drivers/media/usb/uvc/uvc_driver.c | 80 -------------------------- drivers/media/usb/uvc/uvc_v4l2.c | 14 ++--- drivers/media/usb/uvc/uvcvideo.h | 3 - drivers/media/v4l2-core/v4l2-common.c | 82 +++++++++++++++++++++++++++ include/media/v4l2-common.h | 4 ++ 5 files changed, 93 insertions(+), 90 deletions(-) diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index 7c007426e0827e..cdb92da0f56afd 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -324,86 +324,6 @@ 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://mathforum.org/dr.math/faq/faq.fractions.html - * 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 */ diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c index f4e4aff8ddf771..9aa7ee9950c7b4 100644 --- a/drivers/media/usb/uvc/uvc_v4l2.c +++ b/drivers/media/usb/uvc/uvc_v4l2.c @@ -380,7 +380,7 @@ static int uvc_v4l2_get_streamparm(struct uvc_streaming *stream, mutex_unlock(&stream->mutex); denominator = 10000000; - uvc_simplify_fraction(&numerator, &denominator, 8, 333); + v4l2_simplify_fraction(&numerator, &denominator, 8, 333); memset(parm, 0, sizeof(*parm)); parm->type = stream->type; @@ -421,7 +421,7 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream, else timeperframe = parm->parm.output.timeperframe; - interval = uvc_fraction_to_interval(timeperframe.numerator, + interval = v4l2_fraction_to_interval(timeperframe.numerator, timeperframe.denominator); uvc_dbg(stream->dev, FORMAT, "Setting frame interval to %u/%u (%u)\n", timeperframe.numerator, timeperframe.denominator, interval); @@ -475,7 +475,7 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream, /* Return the actual frame period. */ timeperframe.numerator = probe.dwFrameInterval; timeperframe.denominator = 10000000; - uvc_simplify_fraction(&timeperframe.numerator, + v4l2_simplify_fraction(&timeperframe.numerator, &timeperframe.denominator, 8, 333); if (parm->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) { @@ -1267,7 +1267,7 @@ static int uvc_ioctl_enum_frameintervals(struct file *file, void *fh, fival->discrete.numerator = frame->dwFrameInterval[index]; fival->discrete.denominator = 10000000; - uvc_simplify_fraction(&fival->discrete.numerator, + v4l2_simplify_fraction(&fival->discrete.numerator, &fival->discrete.denominator, 8, 333); } else { fival->type = V4L2_FRMIVAL_TYPE_STEPWISE; @@ -1277,11 +1277,11 @@ static int uvc_ioctl_enum_frameintervals(struct file *file, void *fh, fival->stepwise.max.denominator = 10000000; fival->stepwise.step.numerator = frame->dwFrameInterval[2]; fival->stepwise.step.denominator = 10000000; - uvc_simplify_fraction(&fival->stepwise.min.numerator, + v4l2_simplify_fraction(&fival->stepwise.min.numerator, &fival->stepwise.min.denominator, 8, 333); - uvc_simplify_fraction(&fival->stepwise.max.numerator, + v4l2_simplify_fraction(&fival->stepwise.max.numerator, &fival->stepwise.max.denominator, 8, 333); - uvc_simplify_fraction(&fival->stepwise.step.numerator, + v4l2_simplify_fraction(&fival->stepwise.step.numerator, &fival->stepwise.step.denominator, 8, 333); } diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index 2e5366143b8144..a61cd0a459e88d 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -906,9 +906,6 @@ int uvc_xu_ctrl_query(struct uvc_video_chain *chain, struct uvc_xu_control_query *xqry); /* Utility functions */ -void uvc_simplify_fraction(u32 *numerator, u32 *denominator, - unsigned int n_terms, unsigned int threshold); -u32 uvc_fraction_to_interval(u32 numerator, u32 denominator); struct usb_host_endpoint *uvc_find_endpoint(struct usb_host_interface *alts, u8 epaddr); diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c index df34b2a283bc29..1d0b56249ca0e1 100644 --- a/drivers/media/v4l2-core/v4l2-common.c +++ b/drivers/media/v4l2-core/v4l2-common.c @@ -482,3 +482,85 @@ s64 v4l2_get_link_freq(struct v4l2_ctrl_handler *handler, unsigned int mul, return freq > 0 ? freq : -EINVAL; } EXPORT_SYMBOL_GPL(v4l2_get_link_freq); + +/* 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 v4l2_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://mathforum.org/dr.math/faq/faq.fractions.html + * 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); +} +EXPORT_SYMBOL_GPL(v4l2_simplify_fraction); + +/* 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 v4l2_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; +} +EXPORT_SYMBOL_GPL(v4l2_fraction_to_interval); diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h index 3eb202259e8ccd..df4ad81251195e 100644 --- a/include/media/v4l2-common.h +++ b/include/media/v4l2-common.h @@ -540,6 +540,10 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat, s64 v4l2_get_link_freq(struct v4l2_ctrl_handler *handler, unsigned int mul, unsigned int div); +void v4l2_simplify_fraction(u32 *numerator, u32 *denominator, + unsigned int n_terms, unsigned int threshold); +u32 v4l2_fraction_to_interval(u32 numerator, u32 denominator); + static inline u64 v4l2_buffer_get_timestamp(const struct v4l2_buffer *buf) { /*