P
Paul
This is all about Plug and Play.Seum said:
Certain types of hardware have numbers stored in them, used to
identify them. The OS knows how to read the numbers. Once the
numbers are known, the OS goes about checking its collection
of drivers, to see if a driver "fits". The INF files contain
the Plug and Play collections, and that is one thing the
OS consults first.
And this is why, I compare the Plug and Play numbers, against
the contents of all the INF files, basically doing the same thing
the OS does.
You have to do a "text search" on the collection of INF files,
to find the necessary info. It isn't the "file name" that
contains the info, it's the "contents" of the file that
contain the info.
Let's work with an example. These are two lists of Plug and Play
numbers you can bookmark for the future.
http://www.linux-usb.org/usb.ids (USB bus devices)
http://pciids.sourceforge.net/pci.ids (PCI or PCI Express or AGP perhaps)
USB devices use "VID" and "PID", while PCI devices use
"VEN" and "DEV". Those terms help identify which bus a
device is on. The "V" standard for "Vendor" or the company
that designed and manufactured the chip. Note that many
chips have dynamic identities (the ID can be changed when
a different company makes a product), but the principle of
the matching process of the numbers is not changed. In
principle, the "SUBSYS" field is supposed to identify
variants, but in practice, that convenience got violated.
Some devices can be very hard to trace down, to a
datasheet, due to the ability to override the hardware
constant value, with info stored in a serial EEPROM.
I'll use the first web page. The ellipsis mark sections of
file that I didn't copy. This is the "usb.ids" web page.
# List of USB ID's
#
# Maintained by Stephen J. Gowdy <email address deleted...>
...
03ee Mitsumi
...
6901 SmartDisk FDD
6902 Floppy Disk Drive
Now, if I go to C:\Windows\INF and do a textual (contents) search
of every .inf file in there, I'll get a hit in "usbstor.inf".
The USBstor file is for USB storage devices. This is from my
current WinXP machine.
[Mitsumi]
...
%USB\VID_03EE&PID_6901.DeviceDesc%=USBSTOR_CBI
The first floppy is in the file, the second floppy design is not.
I have a copy of my Windows 7 laptop C: drive on the computer as well.
It has a Windows\INF\usbstor.inf as well, with the same lines in it.
A line available for the 6901 model, none for the 6902 model.
USB devices consist of devices with standard interfaces, or devices
with custom interfaces. A device with a standard interface, may
install immediately, because the OS has "USB stack" drivers for the
various standards. The usb.org site, has a list of the standard
interfaces ("classes") for USB, and those standards are the ones
Microsoft uses to maintain orderly USB support. For example,
"USB Mass Storage" is a standard interface for USB hard drive boxes.
If a device has a custom interface, then you're more likely to
need a separate driver package. Some cheesy webcams are like that -
they're not UVC (USB Video Class) standard devices, and need
a custom driver and firmware loader to make them work.
*******
In WinXP, I have a
C:\Windows\setupapi.log
file, while the Windows 7 system has
C:\Windows\inf\setupapi.app.log
C:\Windows\inf\setupapi.dev.log <---- logs hardware installs ???
C:\Windows\inf\setupapi.offline.log
If you have the displaying of file extensions disabled on your
computer, then you're not going to see the word "log" on the
end, if you just scroll down that directory. I *always* keep
file extension displaying enabled, for this very reason, so
the full name of the file is displayed at all times. It's one
of the first changes I make, after installing a Windows OS
(part of my Unix background I guess - I can't stand to hide
information like that).
*******
When you get a software installer package, some of the installers
are "stubs". If you look on the CD that comes with a hardware
product, you find the INF file, you'll see a line in the
file that says something like (I don't remember the exact syntax)
include usbstor.inf
which is a way of "calling" the standard Microsoft INF. So
sometimes, when you think you're installing some fancy
software, in fact the installer is using info already
stored on the computer. Maybe the installer simply
includes a text string, identifying the product in
Device Manager. A scheme like that is used for USB2
on chipset drivers, as Microsoft "owns" the USB2 driver,
and manufacturers are not allowed to distribute the files
themselves. That means, virtually any new motherboard you
buy, with USB2, gets the driver from the OS. And not from
some chipset package you happened to install on your own.
The manufacturers are not allowed to put the necessary
USB2 files on their CD. The situation might be different for
USB3, but I don't have any USB3 devices here to check.
Paul
