Re: can device drivers return non-ram via vm_ops->nopage?

From: Jeff Garzik (jgarzik_at_pobox.com)
Date: 03/22/04

  • Next message: Pavel Machek: "Re: swsusp problems [was Re: Your opinion on the merge?]" 
    Date:	Sun, 21 Mar 2004 19:33:42 -0500
To: Russell King <rmk+lkml@arm.linux.org.uk>

    Russell King wrote:
    > On Sun, Mar 21, 2004 at 07:10:53PM -0500, Jeff Garzik wrote:
    >
    >>For the first kind, please read fb_mmap in drivers/video/fbmem.c. Look
    >>at the _horror_ of ifdefs in exporting the framebuffer. And that horror
    >>is what's often needed when letting userspace mmap(2) PCI memory IO regions.
    >
    >
    > Most of this:
    [...]
    > exists because architectures haven't defined their private
    > pgprot_writecombine() implementations, preferring instead to add
    > to the preprocessor junk instead.

    Agreed but the larger point is that that code should not be in fbmem.c
    at all.

    There are two main types of usage for bus IO memory (MMIO), data and
    hardware registers. Both types driver writers currently export to
    userspace via mmap(2). Caching and write combining are simply
    driver-controlled attributes one must consider.

            Jeff

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  • Next message: Pavel Machek: "Re: swsusp problems [was Re: Your opinion on the merge?]"