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    Subjectv4l device in userspace
    >>>>> "Salvatore" == Salvatore Sanfilippo <antirez@gmail.com> writes:

    Salvatore> Hello, I'm trying to implement a v4l device driver for
    Salvatore> symbian based smart phones. In theory it is very
    Salvatore> simple:

    Salvatore> I've a little program running in the phone, capturing
    Salvatore> images from the camera and sending it to the linux box
    Salvatore> via bluetooth.

    Salvatore> In the linux box side, I've a deamon capturing this
    Salvatore> images (via a bluetooth SP channel), and.... I've to
    Salvatore> pass the images to a fake v4l device driver that
    Salvatore> actually gets the images form userspace.

    Salvatore> Basically I've to pass by the kernel just for the
    Salvatore> interface, and not to do real kernel-side work (like to
    Salvatore> access to the some kind of hardware).

    Salvatore> So I've some questions ( thanks in advance for any
    Salvatore> reply).

    Salvatore> 1) What's the best way to pass relatively high-band
    Salvatore> data between the v4l fake driver and userspace? A char
    Salvatore> device will do the work? ioctl?

    Salvatore> 2) What about some way to handle ioctl directly from
    Salvatore> userspace? Given this support I may implement the whole
    Salvatore> code in userspace. And I guess there are a lot of
    Salvatore> other real world problems that can be handled in
    Salvatore> userspace given the ability to handle ioctl from there.

    Salvatore> If you think 2) is reasonable I may actually implement
    Salvatore> some simple form of generic char driver that just
    Salvatore> allows userspace programs to handle read/write/ioctl
    Salvatore> opreations, and then use this to fix my real issue.

    Salvatore> Thank you very much for the help, and sorry if there is
    Salvatore> something conceptually wrong in my questions.

    Sounds like you should take a look at the v4l loopback device
    (http://www.lavrsen.dk/twiki/bin/view/Motion/VideoFourLinuxLoopbackDevice).
    Otherwise it may be better to ask the question on the v4l mailing list
    (https://listman.redhat.com/mailman/listinfo/video4linux-list).

    Anyway, since you already capture the video, why do you have to pipe
    it through a v4l device?

    Marcus

    --
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    | Dr. Marcus O.C. Metzler | |
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