Hello all,
I wonder if the this may be of interest to Haifux members.
During my work I become acquainted with the Linux USB Subsystem Layer.
The need for it came in when using Video4Linux drivers in developing a
VideoConference
application on linux.
Usually, when running on Intel x86 platforms, there is no
problem with Video4Linux drivers; many drivers are now a part of
the kernel in most distros; so you insert a WebCam and it is identified
and automatically the driver in loaded; in some cases you need to find out which
driver you need and build it.
Problems can arise when you use non Intel platforms, like ARM or PPC.
And I did encounter some problems (certain WebCams did not work) which forced
me to delve into the USB systems
topics :
========
A short Intro on the Universal Serial Bus
(USB Host Controllers (usb-ohci and usb-uhci) ;
Enumeration and Device Descriptors ; What is a URB ? USB2)
Descriptors: Info in /proc/bus/usb/devices (Endpoints; parameters like
MxPS,Configurations,etc.)
Vidoe4Linux drivers (focusing on PWC and Ov511 families)
Hotplug of usb devices
USB completion handlers
Configuring USB Devices
USB transfers (there are 3 types : Bulk transfers ; Interrupt transfers ;
and isochronous (ISO) transfers ; I will focus on isochronous (ISO) transfers
since there are what is common in most WebCams)
How to know if a certain WebCam is supported by Linux and which driver it needs?
USB Programming
I must warn that most of these topics are purely technical, and usually are NOT
needed in real life except if you are working with some Embedded Systems
/developing USB drivers
(and also there, if you work with Intel bases processors , usually there is no
problem;
it is plug and play) ; And I can focus only on Video4Linux devices , since
I know a little about other USB devices (like USB HardDisk,USB DiskOnKey,USB
mouse,etc.)
Moreover , it can be at least 2 months from now.
I would like to hear your opinion.
Regards,
Rami Rosen
נשלח באמצעות קולמייל, דואר הרשת הטוב בישראל.
http://coolmail.nana.co.il
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