[MPlayer-dev-eng] [PATCH] v4l/v4l2 buffer size bug

[Alan Curry]

Ivan Kalvachev writes the following:
>
>2006/4/25, Alan Curry <pacman at theworld.com>:
>>
>> mem_unit hasn't always been there. Detecting whether the running kernel
>> supports mem_unit, and doing the right thing when <sys/sysinfo.h> contains
>> the old struct definition without mem_unit, is left as an exercise for the
>> v4l maintainer.
>
>i don't see such person in docs/tech/maintainers.

    * TV input/capture: Jindrich Makovicka

>You'd better do the exercise yourself and send patch before commit.

All right then...

There was no explicit upper limit on buffersize, which defaults to half of
totalram. This patch caps it at 2G. Someone more familiar with real usage
scenarios, please comment on this upper bound and propose a better one.

I don't have the hardware, so I can't test this, but it compiles.

Index: libmpdemux/tvi_v4l.c
===================================================================
RCS file: /cvsroot/mplayer/main/libmpdemux/tvi_v4l.c,v
retrieving revision 1.78
diff -u -r1.78 tvi_v4l.c
--- libmpdemux/tvi_v4l.c	21 Apr 2006 12:47:37 -0000	1.78
+++ libmpdemux/tvi_v4l.c	25 Apr 2006 22:06:34 -0000
@@ -750,12 +750,20 @@
     } else {
 #ifdef HAVE_SYS_SYSINFO_H
 	struct sysinfo si;
+	unsigned long long totalram;
 	
 	sysinfo(&si);
-	if (si.totalram<2*1024*1024) {
+	totalram = si.totalram;
+#ifdef HAVE_SYSINFO_MEM_UNIT
+	if (si.mem_unit)
+	    totalram *= si.mem_unit;
+	if (totalram > (1ULL<<32) - 1)
+	    totalram = (1ULL<<32) - 1;
+#endif
+	if (totalram<2*1024*1024) {
 	    bufsize = 1024*1024;
 	} else {
-	    bufsize = si.totalram/2;
+	    bufsize = totalram/2;
 	}
 #else
 	bufsize = 16*1024*1024;
Index: libmpdemux/tvi_v4l2.c
===================================================================
RCS file: /cvsroot/mplayer/main/libmpdemux/tvi_v4l2.c,v
retrieving revision 1.39
diff -u -r1.39 tvi_v4l2.c
--- libmpdemux/tvi_v4l2.c	22 Apr 2006 05:12:10 -0000	1.39
+++ libmpdemux/tvi_v4l2.c	25 Apr 2006 22:06:40 -0000
@@ -1131,12 +1131,20 @@
     } else {
 #ifdef HAVE_SYS_SYSINFO_H
 	struct sysinfo si;
+	unsigned long long totalram;
 	
 	sysinfo(&si);
-	if (si.totalram<2*1024*1024) {
+	totalram = si.totalram;
+#ifdef HAVE_SYSINFO_MEM_UNIT
+	if (si.mem_unit)
+	    totalram *= si.mem_unit;
+	if (totalram > (1ULL<<32) - 1)
+	    totalram = (1ULL<<32) - 1;
+#endif
+	if (totalram<2*1024*1024) {
 	    bufsize = 1024*1024;
 	} else {
-	    bufsize = si.totalram/2;
+	    bufsize = totalram/2;
 	}
 #else
 	bufsize = 16*1024*1024;
Index: configure
===================================================================
RCS file: /cvsroot/mplayer/main/configure,v
retrieving revision 1.1178
diff -u -r1.1178 configure
--- configure	25 Apr 2006 01:38:02 -0000	1.1178
+++ configure	25 Apr 2006 22:07:11 -0000
@@ -3349,6 +3349,25 @@
 fi
 echores "$_sys_sysinfo"
 
+_sysinfo_mem_unit=no
+if test "$_sys_sysinfo" = yes ; then
+    echocheck "mem_unit field in sysinfo"
+    cat > $TMPC << EOF
+#include <sys/sysinfo.h>
+int main(void) {
+  struct sysinfo s_info;
+  sysinfo(&s_info);
+  return s_info.mem_unit>0;
+}
+EOF
+    cc_check && _sysinfo_mem_unit=yes
+    if test "$_sysinfo_mem_unit" = yes ; then
+      _def_sysinfo_mem_unit='#define HAVE_SYSINFO_MEM_UNIT 1'
+    else
+      _def_sysinfo_mem_unit='#undef HAVE_SYSINFO_MEM_UNIT'
+    fi
+    echores "$_sysinfo_mem_unit"
+fi
 
 echocheck "Mac OS X APIs"
 if test "$_macosx" = auto && darwin ; then
@@ -7585,6 +7604,9 @@
 /* Define this if your system has the sysinfo header */
 $_def_sys_sysinfo
 
+/* Define this if your struct sysinfo contains the mem_unit field */
+$_def_sysinfo_mem_unit
+
 /* Define this if your system has ftello() */
 
 $_def_ftello