[Qemu-discuss] How can I get the framebuffer's address of qemu-riscv

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Dear Mr or Mrs,
        I'm running my bare-mental examples on qemu-riscv. And I want to 
implement API to draw video of qemu-riscv. So I have to know the address of 
framebuffer. I have seen qemu-i386 and find that the pointer to framebuffer is 
included in VESA BIOS Extension. However, it isn't suitable for qemu-riscv. So 
how can I get the framebuffer's address of qemu-riscv? which manual should I 
read? Please help me.
        Best Regards,
        Thx