Re: user_to_phys() without mmap?

I'm trying to use a framebuffer from user space (think plain video ram,
not some PCI or AGP video card), but mmap'ing from kernel space into
user space is causing large latencies and unsightly artifacts.

Maybe you should map it uncached?

You're right. I was already using ioremap_nocache(), so I didn't realize that I had to specify anything additional when using remap_page_range(). But I added this, and everything started working as desired.

pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE|_PAGE_GUARDED;

Just one thing though: why not use the Linux framebuffer interface?

I'm using this for a special purpose proof-of-concept, and although I need this to work, it really is not a central part of my work. Honestly, the framebuffer interface looked like it would be more complicated to use in my case. I usually opt for the Right Way, but this time I took the shortcut. ;)

Thanks for your comments. They helped me get this worked out.
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