让硬件正常工作（一）

让硬件正常工作（一）

问题的描述：

先说明一下“系统”，并不是单纯的指内核，也包括一些与硬件有关的用户程序特性。

• I plug in my new digital camera.
  
• If the camera's interface type (e.g. USB) supports it, the presence of a new device is noticed without user intervention.
  
• For devices that can't be detected on plugin, there's some GUI application allowing me to explicitly probe or specify the device information.
  
• The system gets whatever information is available from the device about the hardware model. Vendor, ProdID, whatever it can get.
  
• The system consults a mapping from hardware model information to driver information. This mapping is created by merging three sources of information: user-provided information, OEM-provided information, and operating-system-vendor-provided information.
  
• If no driver is found, the system delivers a notification to the desktop environment, and the desktop environment informs the user that the device is not supported. Alternatively, the desktop environment asks the user which driver to try and passes the answer back to the system; the system a) tries that driver and b) saves the driver information in the above-mentioned mapping so it won't have to ask in the future.
  
• The system loads a driver once one has been found in the mapping, or added to the mapping.
  
• One or more kernel devices are created by the driver (implying major/minor pair, and /dev file if required).
  
• A notification is sent out from the system to all interested listeners that a new kernel device has been created.
  
• The user's desktop environment asks the system what sort of device is represented by the new kernel device: camera, scanner, printer, etc.
  
• If the system does not know, it says "device type is unknown."
  
• If the device type is unknown, the desktop environment asks the user to provide it. "What did you just plug in?"
  
• After the user provides this information, the desktop environment passes it back to the system. The system records a mapping from the hardware model identifying information to the device type. Next time a kernel device is created for a physical device with the same model information, the system will report its type accordingly.
  
• The desktop environment allows the user to interact with the device in device-appropriate ways. For example, view images from a camera, monitor errors from a printer, or whatever.

整理如下：
1、把自己的相机插入到电脑的usb口上。
2、如果相机的界面类型，比如usb，系统能够提供支持，那不需要用户的干涉，系统会出现一个“新的设备通知”。
3、对于不能被侦测到的设备（比如我的相机插入后系统没有任何反应），有一些图形界面的应用程序会允许我扫描设备并且指定相关的信息。
4、系统可以从相机上获得诸如hardware model. Vendor, ProdID这样的信息，这些都是很有用的。
5、系统参照从硬件型号到设备驱动的映射信息。这个映射信息由用户输入的信息，产品提供的信息以及系统提供的信息组合而成。

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