Ilan Finci wrote:
Thanks,
I've looked at the code of do_div on PPC, and it uses % and /. Will it
still work?
Also, I tried to use do_div on i386 (kernel 2.4.18), and I get wrong
answer. Attached is a small test program, where do_div is the version
from the i386 sources, and do_div1 is the version from PPC sources.
The first one give wrong answer, while the second one works fine. What
am I missing? Will the code in v4l2 that uses do_div works on Intel
platforms?
Thanks,
Ilan
Gerd Knorr wrote:
/lib/modules/2.4.16/kernel/drivers/media/video/videodevX.o:
unresolved symbol __udivdi3
/lib/modules/2.4.16/kernel/drivers/media/video/videodevX.o:
unresolved symbol __umoddi3
libgcc functions for 64bit math, which are not present in the kernel
because it isn't linked against libgcc.
I see in videodevX.c that the function v4l2_math_div6432(...) I see
that for intel cpus, there is an assembly code, and for others, a use
of the '/' and '%', can this be the problem?
Yes.
The modules in http://bytesex.org/patches/12_v4l2-2.4.19-pre2.diff.gz
have this fixed, they use the kernel functions for 64bit division.
Gerd
Attached is a completely untested patch (well, it does build...) for
videodevX, that adds Gerd's math routines. Please give it a try, and
let me know if it works.
-justin
diff -urN videodevX/videodev.h videodevX-newdiv/videodev.h
--- videodevX/videodev.h Thu Jun 14 07:45:23 2001
+++ videodevX-newdiv/videodev.h Thu Mar 14 10:58:56 2002
@@ -879,9 +879,6 @@
extern void *v4l2_q_yank_node(struct v4l2_queue *q, struct v4l2_q_node *node);
extern int v4l2_q_last(struct v4l2_queue *q);
-/* Math functions */
-extern u32 v4l2_math_div6432(u64 a, u32 d, u32 *r);
-
/* Time functions */
extern unsigned long v4l2_timestamp_divide(stamp_t t,
unsigned long p_100ns);
diff -urN videodevX/videodevX.c videodevX-newdiv/videodevX.c
--- videodevX/videodevX.c Thu Jun 14 07:45:23 2001
+++ videodevX-newdiv/videodevX.c Thu Mar 14 11:03:42 2002
@@ -42,19 +42,18 @@
* 2.4 devfs support ported from 2.4 kernels by
* Dan Merillat <dan@xxxxxxxxxxxx>
* Added Gerd Knorrs v4l1 enhancements (Justin Schoeman)
+ * Arch independant division hacked for Gerd Knor's v4l2 patch
*/
#ifndef __KERNEL__
#define __KERNEL__
#endif
-
#include <linux/config.h>
#ifndef EXPORT_SYMTAB
#define EXPORT_SYMTAB
#endif
-
#include <linux/version.h>
#include <linux/module.h>
#include <linux/types.h>
@@ -66,13 +65,13 @@
#include <linux/errno.h>
#include "videodev.h"
-
#if LINUX_VERSION_CODE >= 0x020100
#include <asm/uaccess.h>
#endif
#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/io.h>
+#include <asm/div64.h>
#ifdef CONFIG_KMOD
#include <linux/kmod.h>
@@ -1132,7 +1131,7 @@
int count, int *eof, void *data)
{
int len = 0;
- struct videodev_proc_data *d;
+ struct videodev_proc_data *d = NULL;
struct list_head *tmp;
list_for_each (tmp, &videodev_proc_list) {
@@ -1765,41 +1764,15 @@
* Math functions
*/
-u32
-v4l2_math_div6432(u64 a, u32 d, u32 *r)
-{
- u32 q, m;
-#ifdef __i386__
-/* Danger: This function will fault if the quotient exceeds (1<<32) - 1 */
- __asm__ __volatile__ (
- " movl %2,%%eax\n"
- " movl %3,%%edx\n"
- " divl %4\n"
- " movl %%eax,%0\n"
- " movl %%edx,%1\n"
- : "=g" (q), "=g" (m)
- : "g" ((u32)a), "g" ((u32)(a >> 32)), "g" (d)
- : "eax", "edx"
- );
-#else
- q = a / d;
- m = a % d;
-#endif
- if (r) *r = m;
- return q;
-}
-
unsigned long
v4l2_timestamp_divide(stamp_t t, unsigned long p_100ns)
{
- /* Note: 't' is in 1ns units, 'p_100ns' is in 100ns units, */
- /* and the quotient is rounded */
- u64 p;
-
- p = (u64)p_100ns * 100; /* 1ns units */
- t >>= 6; /* /64 to allow p_100ns longer than 4 secs. */
- p >>= 6; /* to keep quotient the same */
- return v4l2_math_div6432((u64)t + (p >> 1), (u32)p, NULL);
+ u32 p;
+
+ p = ((u64)p_100ns * 100) >> 6;
+ t = (t >> 6) + (p >> 1);
+ do_div(t,p);
+ return t;
}
/* Force the timestamp to be an integer multiple of p_100ns */
@@ -1877,13 +1850,16 @@
unsigned long
v4l2_video_std_tpf(struct v4l2_standard *vs)
{
- return v4l2_math_div6432(
- (u64)vs->framerate.numerator * 10000000
- + vs->framerate.denominator / 2,
- vs->framerate.denominator,
- NULL);
+ u64 a;
+ u32 b;
+
+ a = (u64)vs->framerate.numerator * 10000000 + vs->framerate.denominator / 2;
+ b = vs->framerate.denominator;
+ do_div(a,b);
+ return a;
}
+
/* Used only in v4l2_video_std_confirm() */
static void
catc1p2e6(__u8 *s, char c, int n)
@@ -2139,7 +2115,6 @@
EXPORT_SYMBOL(v4l2_q_peek_tail);
EXPORT_SYMBOL(v4l2_q_yank_node);
EXPORT_SYMBOL(v4l2_q_last);
-EXPORT_SYMBOL(v4l2_math_div6432);
EXPORT_SYMBOL(v4l2_timestamp_divide);
EXPORT_SYMBOL(v4l2_timestamp_correct);
EXPORT_SYMBOL(v4l2_masterclock_register);
