V4L2-library February 2008

v4l2-library@linuxtv.org

4 participants
3 discussions

Re: [V4l2-library] [RFC 1/1] v4l2_extension: helper daemon commands passing
by Jiri Slaby 25 Feb '08

25 Feb '08

On 02/22/2008 09:25 PM, Thierry Merle wrote: > Jiri Slaby a écrit : >> Here I would like to know if the the commands passing interface to the >> helper daemon introduced in this patch is OK, or alternatively propose >> some other idea ;). >> > It is a good starting point. > All ioctls will be processed in the helper daemon via the process_ioctl > command. > read/write processings make less context switchings than ioctls. > Further, mmap will be required to pass the compressed/uncompressed frames. > > The point to think about is how to identify the base driver when we > reach the process_ioctl function. > The helper daemon must behave in a specific way for each base driver to > extend. I was thinking about yet another thing. Maybe the driver should pass to the ext layer, which conversions should be done. I mean for example vert./horiz. flip, image rotation, which has nothing to do with V4l, but some cameras might want this (stk11xx is good/bad example ;)). In this case no matter of chosen format, every frame must go through the daemon to process the conversion. So I was also thinking about passing to the ext layer in which (non-v4l = upside-down) formats the driver can emit frames (or layer can ask through v4l ioctl callbacks). Or just letting this on the base driver? > I see 2 solutions: > - identify the base driver at each request between the extended driver > and the helper daemon, > - instanciate a helper daemon for each base driver (that means > concurrent accesses to /dev/v4l2_extension) But how to distinguish the application accessing the node then? > Identify the base driver means the helper daemon must know its > capabilities, not only its name. Yes. But it must in any way, needn't it? (To not return yet enumered formats for example.) I don't know, both have their pros and cons.

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Joint, on board :-)
by Thomas Kaiser 23 Feb '08

23 Feb '08

Hi You may read my name already on the V4l mail list. I am pleased to join this list :-) I just read http://www.linuxtv.org/v4lwiki/index.php/V4L2UserspaceLibrary (I did not look at the code, yet) Looks very good. But how you will get the raw stream from the V4l1/2 device? As far as I know, this is not defined by V4l. That's way I asked for V4L2_PIX_FMT_RAW on the v4l mail list. Thomas -- http://www.kaiser-linux.li

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Re: [V4l2-library] [PATCH 4/4] v4l2_extension: grab real driver reference
by Thierry Merle 15 Feb '08

15 Feb '08

Thierry Merle a écrit : > Jiri Slaby a écrit : > >> From: Jiri Slaby <ku(a)bellona.localdomain> >> >> Before opening real backing device, make sure, it is there and not going away. >> Drop the reference after release and failing open. >> >> Signed-off-by: Jiri Slaby <jirislaby(a)gmail.com> >> --- >> > All this patch series is comitted in > http://linuxtv.org/hg/~tmerle/v4l2_extension , thanks. > > > -- > video4linux-list mailing list > Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe > https://www.redhat.com/mailman/listinfo/video4linux-list > > Argh, I did not notice, this patch series is for the v4l2 library, not for the v4l-dvb mainstream. Sorry people, wrong list :) Thierry

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V4L2-library February 2008