Re: USB mini-summit at LinuxCon Vancouver

From: Theodore Kilgore
Date: Tue Aug 09 2011 - 19:02:25 EST

On Tue, 9 Aug 2011, Hans de Goede wrote:

> Hi,
> On 08/09/2011 04:19 PM, Alan Stern wrote:
> > On Tue, 9 Aug 2011, Hans de Goede wrote:
> >
> > > I would really like to see the dual mode camera and TV tuner discussion
> > > separated. They are 2 different issues AFAIK.
> > >
> > > 1) Dual mode cameras:
> > >
> > > In the case of the dual mode camera we have 1 single device (both at
> > > the hardware level and at the logical block level), which can do 2 things,
> > > but not at the same time. It can stream live video data from a sensor,
> > > or it can retrieve earlier taken pictures from some picture memory.
> > >
> > > Unfortunately even though these 2 functions live in a single logical
> > > block,
> > > historically we've developed 2 drivers for them. This leads to fighting
> > > over device ownership (surprise surprise), and to me the solution is
> > > very clear, 1 logical block == 1 driver.
> >
> > According to Theodore, we have developed 5 drivers for them because the
> > stillcam modes in different devices use four different vendor-specific
> > drivers.
> Yes, but so the the webcam modes of the different devices, so for
> the 5 (not sure if that is the right number) dual-cam mode chipsets
> we support there will be 5 drivers, each supporting both the
> webcam and the access to pictures stored in memory of the chipset
> they support. So 5 chipsets -> 5 drivers each supporting 1 chipset,
> and both functions of the single logical device that chipset
> represents.
> > Does it really make sense to combine 5 drivers into one?
> Right, that is not the plan. The plan is to simply stop having 2 drivers
> for 1 logical (and physical) block. So we go from 10 drivers, 5 stillcam
> + 5 webcam, to just 5 drivers. We will also likely be able to share
> code between the code for the 2 functionalities for things like generic
> set / get register functions, initialization, etc.

Probably this is a good time for some inventory to be done.

sure of the exact number of drivers. The jeilinj driver does not count
here. It is a standard mass storage device as a still camera, and if it is
going to be hooked up as a webcam then it has to have some buttons pushed
just so, prior to hookup -- after which it comes up with a different USB
Product number as a proprietary webcam device, supported by the jeilinj
driver. Thus, this is not one of the droids we are looking for.

Specifically, the currently affected drivers are sq905, sq905c, mr97310a,
and sn9c2028.

Fuji Finepix seems to produce both still cameras (PTP protocol) and
webcams. If there are currently any dual-mode cameras, it is not obvious.
Perhaps any of these which can be dual mode are like the jeilinj cameras
and come up under different Product numbers in the different modes, which
is not a problem.

There do seem to exist stv06xx dual-mode cameras:

stv0680/stv0680.c: { "STM:USB Dual-mode camera", 0x0553, 0x0202, 1

is found in camlibs/stv0680, for example, along with a whole bunch of
other cameras with the same Vendor:Product number. It seems, too, that the
same Vendor:Product number is listed in gspca/stv0680.c

So I guess we found another affected driver.

The intersection seems to be void between the lists of the spca50x cameras
and webcams, though one can not be certain about the future. I do know of
another dualmode camera, powered by the JL2005A chip. I wrote a kernel
module for it some months ago. Said module has not been sent upward
because of mysterious issues with one of the three cameras used for
testing it.

We also find among the gspca driver files this

* GSPCA sub driver for W996[78]CF JPEG USB Dual Mode Camera Chip.
* Copyright (C) 2009 Hans de Goede <hdegoede@xxxxxxxxxx>

but I am not sure about which cameras are using this.

Theodore Kilgore
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