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Thread: atombios VRAM_UsageByFirmwareTable and ARG_FB

  1. #1
    Join Date
    Dec 2008
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    Question atombios VRAM_UsageByFirmwareTable and ARG_FB

    In atom_allocate_fb_scratch in atom.c, scratch is allocated in kernel RAM based on the VRAM_UsageByFirmwareTable or harcoded to 20kB.

    What's the story about this table and the hardcoded value?

    Indeed, the "VRAM...table" is supposed to target VRAM, isn't it?
    Moreover, ARG_FB for the atombios means Frame Buffer, I presume?

  2. #2
    Join Date
    Dec 2007
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    Quote Originally Posted by sylware View Post
    In atom_allocate_fb_scratch in atom.c, scratch is allocated in kernel RAM based on the VRAM_UsageByFirmwareTable or harcoded to 20kB.

    What's the story about this table and the hardcoded value?
    It specifies the max size of the scratch buffer used by the vbios. If for some reason the table is empty the default value is 20k.

    Quote Originally Posted by sylware View Post
    Indeed, the "VRAM...table" is supposed to target VRAM, isn't it?
    Moreover, ARG_FB for the atombios means Frame Buffer, I presume?
    It doesn't matter. It's just a scratch buffer for storing large buffers required by some command tables. When the command tables are called during real mode post, they use vram to avoid using system memory, but when the driver is loaded, you can just use system memory.

  3. #3
    Join Date
    Dec 2008
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    166

    Thumbs up

    All right!

    The name is based on POST real mode behavior!

    Thx.

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