Re: v4l2 kernel module debugging methods
On Fri, Dec 11, 2015 at 10:50 AM, Fabien DESSENNEwrote: > Hi Ran, > > On 12/10/2015 10:46 PM, Ran Shalit wrote: >> On Sun, Dec 6, 2015 at 2:23 AM, Nicolas Dufresne >> 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 Thank you very much for the helpful ideas. Regards, Ran -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: v4l2 kernel module debugging methods
Hi Ran, On 12/10/2015 10:46 PM, Ran Shalit wrote: > On Sun, Dec 6, 2015 at 2:23 AM, Nicolas Dufresne >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 FabienN�r��yb�X��ǧv�^�){.n�+{���bj)w*jg����ݢj/���z�ޖ��2�ޙ&�)ߡ�a�����G���h��j:+v���w��٥
Re: v4l2 kernel module debugging methods
On Sun, Dec 6, 2015 at 2:23 AM, Nicolas Dufresnewrote: > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: v4l2 kernel module debugging methods
Le jeudi 10 décembre 2015 à 23:46 +0200, Ran Shalit a écrit : > 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 ? I never used that, printing I used. You should also run v4l2- compliance. It's a test suite, part of v4l-utils. Nicolas signature.asc Description: This is a digitally signed message part
v4l2 kernel module debugging methods
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 ? Any other methods, tips, about validation, testing and developing a v4l2 device is appreciated. Best Regards, Ran -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: v4l2 kernel module debugging methods
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 signature.asc Description: This is a digitally signed message part