Hi Ran, On 12/10/2015 10:46 PM, Ran Shalit wrote: > On Sun, Dec 6, 2015 at 2:23 AM, Nicolas Dufresne > <nicolas.dufresne@xxxxxxxxxxxxx> wrote: >> Le dimanche 06 décembre 2015 à 00:00 +0200, Ran Shalit a écrit : >>> Hello, >>> >>> I would like to ask a general question regarding methods to debug a >>> v4l2 device driver. >>> Since I assume that the kernel driver will probably won't work in >>> first try after coding everything inside the device driver... >>> >>> 1. Do you think qemu/kgdb debugger is a good method for the device >>> driver debugging , or is it plain printing ? >>> >>> 2. Is there a simple way to display the image of a YUV-like buffer in >>> memory ? >> >> Most Linux distribution ships GStreamer. You can with GStreamer read >> and display a raw YUV images (you need to know the specific format) >> using videoparse element. >> >> gst-launch-1.0 filesrc location=my.yuv ! videoparse format=yuy2 width=320 height=240 ! imagefreeze ! videoconvert ! autovideosink >> >> You could also encode and store to various formats, replacing the >> imagefreeze ... section with an encoder and a filesink. Note that >> videoparse unfortunatly does not allow passing strides array or >> offsets. So it will work only if you set the width/height to padded >> width/height. >> >> regards, >> Nicolas > > Hi Nicolas, > > Thank you for the comment. > As someone expreinced with v4l2 device driver, do you recommened using > debugging technique such as qemu (or kgdb) or do you rather use plain > printing ? > > Thank you very much, > Ran You can get several level of logs. First, you can enable v4l2 core debug logs. Example: echo 3 > /sys/class/video4linux/video0/debug More details: https://www.kernel.org/doc/Documentation/video4linux/v4l2-framework.txt If the tested driver uses the v4l2_mem2mem framework you can get M2M logs with: echo Y > /sys/module/v4l2_mem2mem/parameters/debug Get also internal vb2 logs with: echo 3 > /sys/module/videobuf2_core/parameters/debug And optionally more logs using the dynamic debug feature: (https://www.kernel.org/doc/Documentation/dynamic-debug-howto.txt). Example: echo "module my_driver +p" > /sys/kernel/debug/dynamic_debug/control Fabien��.n��������+%������w��{.n�����{��g����^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
