Re: v4l2 api compliance test

[Carl Karsten <carl@personnelware.com>]

Andy Walls wrote:
> On Sun, 2008-11-02 at 18:32 -0600, Carl Karsten wrote:
>> Mauro Carvalho Chehab wrote:
>>> On Sat, 01 Mar 2008 01:45:24 -0600
>>> Carl Karsten <carl@personnelware.com> wrote:
>>>
>>>
>>> Please, feel free to improve the tools. Unfortunately, nobody yet had time to
>>> dedicate on improving the testing tools.
>> These 2 issues are thwarting my efforts to write my tester:
>>
>> 1. memory leak:
>> valgrind ./capture --userp -d /dev/video1
>> ==17153== malloc/free: in use at exit: 2,457,632 bytes in 5 blocks.
>>
>> 2. capabilities mismatch:
>> ./capture --userp -d /dev/video1
>> VIDIOC_QBUF error 22, Invalid argument
>>
>> details: http://linuxtv.org/v4lwiki/index.php/Test_Suite#Bugs_in_Examples
>
> I'm not sure why a memory leak on abnormal termination is worrisome for
> you.  It looks like init_userp() allocated a bunch of "buffers", which
> has to happen for a program to use user pointer mode of v4l2.  The
> function errno_exit() doesn't bother to clean up when the VIDIOC_QBUF
> ioctl() call fails.  free() is only called by uninit_device().  Since
> the alternate flow of the program through errno_exit() to termination
> doesn't call free() on "buffers", you should have a process heap memory
> leak on error exit.
>
> Since this is userspace, a memory leak from the process heap doesn't
> hang around when the process terminates - no big deal.

Are you sure about that?

if I run
./capture --userp -d /dev/video1
VIDIOC_QBUF error 22, Invalid argument

enough I can't run the valid modes:

juser@dhcp186:~/vga2usb/v4l.org/examples$ ./capture --read -d /dev/video1
read error 12, Cannot allocate memory

juser@dhcp186:~/vga2usb/v4l.org/examples$ ./capture --mmap -d /dev/video1
mmap error 12, Cannot allocate memory

although free still shows lots:

juser@dhcp186:~/vga2usb/v4l.org/examples$ free
             total       used       free     shared    buffers     cached
Mem:       1033388     282340     751048          0      31012      98208
-/+ buffers/cache:     153120     880268
Swap:       859436          0     859436


> You could
> equally gripe that the program didn't close it's file descriptors with
> the driver on errno_exit() - but process termination cleans those up
> too.

I am personally interested in anything that makes it harder for me to determine
if a driver is misbehaving.

In addition, I would think that the API's example code should be a squeaky clean
example of how real code should be written, given it is often used as a starting
point.  If problems are identified, they should at least be noted, better yet
removed.

Carl K

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