Re: USB mini-summit at LinuxCon Vancouver

From: Hans de Goede
Date: Tue Aug 09 2011 - 15:56:27 EST


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

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

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.


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