Changes between Version 2 and Version 3 of fbf_device_api


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Timestamp:
Jan 20, 2020, 3:55:44 PM (3 years ago)
Author:
alain
Comment:

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  • fbf_device_api

    v2 v3  
    55== __A) General principles__ ==
    66
    7 This device provide access to an external graphic display, that is seen as a fixed size frame buffer, mapped in the kernel address space. The only pixel encoding type in the current implementation is one byte per pixel (256 levels of gray).
     7This device provide access to an external graphic display, that is seen by the kernel as a fixed size frame buffer, mapped in the kernel address space. The only pixel encoding type in the current Almos-mkh implementation is one byte per pixel (256 levels of gray).
    88
    9 It defines a first ''user'' API, used by the user-level system calls, and implementing a simple, kernel controlled, windows manager. This windows manager allows any process to create and use for display one (or several) window(s). Each window defines a private buffer, dynamically allocated in user space, that can be directly accessed (for read and write) by the owner process.
     9It defines a first ''user'' API, used by the user-level system calls, and implementing a simple, kernel controlled, windows manager. This windows manager allows any process to create and use for display one (or several) window(s). Each window defines a private buffer, dynamically allocated in user space, that can be directly accessed (for read and write) by the owner process, without system call.
    1010
    11 These windows can be moved in the frame buffer, they can be resized, they can overlap other windows, but a window must be entirely contained in the frame buffer.
     11These windows can overlap. They can be moved in the frame buffer, or they can be resized, using system calls. The refresh of a window in the FBF must be explicitly required by the owner process. they can overlap other windows,.
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     13A window must be entirely contained in the frame buffer.
    1214
    1315To avoid contention, the window descriptor, and the associated user buffer are not allocated in the cluster containing the FBF chdev, but are distributed: each window is allocated in the cluster defined by the thread that required the window creation.