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    SubjectRe: USB mini-summit at LinuxCon Vancouver


    On Wed, 10 Aug 2011, Mauro Carvalho Chehab wrote:

    > Em 10-08-2011 15:33, Theodore Kilgore escreveu:
    >
    > > Hans seems to have argued cogently for doing all of this in the kernel and
    > > for abandoning the usbfs-based drivers for these particular drivers for
    > > dual-mode cameras and, I would conjecture, for drivers for dual-mode
    > > hardware in general. Therefore, I anticipate that he won't like that very
    > > much.
    > >
    > > My position:
    > >
    > > I do not have preconceptions about how the problem gets handled, and at
    > > this point I remain agnostic and believe that all approaches ought to be
    > > carefully analysed. I can imagine, abstractly, that things like this
    > > could be handled by
    > >
    > > -- moving all basic functionality to the kernel, and fixing the
    > > relevant libgphoto2 drivers to look to the kernel instead of to libusb.
    > > (What Hans argues for, and I am not opposed if his arguments convince
    > > other concerned parties)
    >
    > Not looking on the amount of work to be done, I think that this would
    > give better results, IMO.

    Okay. I would guess that I am one of the guys who gets to do the work,
    though.

    >
    > > -- doing some kind of patch job to make current arrangement somehow to
    > > work better (this seems to be the position of Adam Baker; I do share
    > > the skepticism Hans has expressed about how well this could all be
    > > pasted together)
    >
    > Adam Baker's proposal of a locking between usbfs and the kernel driver seems
    > to be interesting, but, as he pointed, there are some side effects to consider,
    > like suspend/resume, PM, etc.
    >
    > > -- doing something like the previous, but also figuring out how to bring
    > > udev rules into play, which would make it all work better (just tossing
    > > this one in, for laughs, but who knows someone might like it)
    >
    > I don't think this is a good alternative.

    I was trying to mention all alternatives. I should have also mentioned
    "leave things the way they are" but that is certainly out the window.

    >
    > > -- moving the kernel webcam drivers out of the kernel and doing with these
    > > cameras _everything_ including webcam function through libusb. I myself do
    > > not have the imagination to be able to figure out how this could be done
    > > without a rather humongous amount of work (for example, which streaming
    > > apps that are currently available would be able to live with this?) but
    > > unless I misunderstand what he was saying, Greg K-H seems to think that
    > > this would be the best thing to do.
    >
    > I also don't think that this a good alternative. As Hans V. pointed, one of
    > our long term targets is to create per-sensor I2C drivers that are independent
    > from the bridges. Also, moving it to userspace would require lots of work
    > with the duplication of V4L and gspca core into userspace for the devices
    > that would be moved, and may have some performance impacts.

    A good argument, though it probably does not affect the devices on my list
    one way or the other.

    >
    > > Which one of these possibile approaches gets adopted is a policy issue
    > > which I would consider is ultimately way above my pay grade.
    > >
    > > My main motivation for bringing up the issue was to get it to the front
    > > burner so that _something_ gets done. It is a matter which has been left
    > > alone for too long. Therefore, I am very glad that the matter is being
    > > addressed.
    > >
    > > Let me add to this that I have gotten permission for time off and for a
    > > expense money which might possibly cover my air fare. I hope to arrive in
    > > Vancouver by sometime on Monday and intend to attend the mini-summit. I
    > > suggest that we get all intersted parties together and figure out what is
    > > the best way to go.
    > >
    > > I hope everyone who is actively concerned can meet in Vancouver, and if
    > > all goes well then on Monday as well as Tuesday. I can hang around for
    > > another day or two after Tuesday, but I do not expect to register for
    > > LinuxCon or be involved in it.
    >
    > It will be great to have you there for those discussions.

    My take on this was that it seems to have become important for me to
    attend, which, frankly, I was not expecting. So thanks for the nice words.

    >
    > > When I leave Vancouver I will probably go
    > > to Seattle and spend a couple of days with my oldest son, the musician,
    > > before coming home on the next weekend.
    > >
    > > Theodore Kilgore
    >


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