lkml.org 
[lkml]   [2010]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: Can we remove the Zone_DMA?
    From
    Date
    On Son, 2010-04-04 at 01:07 -0400, Daniel Hazelton wrote:
    > On Sunday 04 April 2010 12:21:54 am tek-life wrote:
    > > I’m a newbie on the linux kernel. Now I am reading the source code of
    > > Linux . I have a question in the following about ZONE_DMA.
    > >
    > > In Linux , The Memory is divided to three zone. They are ZONE_DMA
    > > 、ZONE_NORMAL and ZONE_HIGHMEM. From the book of "Undstand the Linux
    > > kernel ", the ZONE_DMA has the effect that the Direct Memory Access
    > > (DMA) processors for old ISA buses have a strong limitation: they are
    > > able to address only the first 16 MB of RAM. SO ,we must set a zone
    > > for the DMA on ISA bus. And I suspect that the hardware has
    > > developed so quickly .And in this days the ISA has been weeded out.

    That doesn't imply that the "old" systems and hardware vanishes (even
    not quickly).

    > > And so ,if we not defined the ZONE_DMA, is the system be effected? And
    > > why not remove ZONE_DMA from the kernel . If it cann‘t to do so,the
    > > compatibility is the only reason?
    >
    > While ISA is gone as a true peripheral interconnect for new systems it does,
    > actually, still live on in a lot of systems that Linux still supports. While
    > those systems, generally, are running the same kernel and userspace they were
    > a decade ago I have no doubt that somebody might find an old machine and put
    > Linux on it - just because they could.
    >
    > And that also discounts the non-IBM PC machines that are out there that Linux
    > also supports. While I don't know enough about them to say for sure, I am
    > quite certain that at least some of them are still using the ISA bus.

    PC-104 has an ISA bus. And it is far from dead and currently deployed
    for new systems.

    Bernd
    --
    Bernd Petrovitsch Email : bernd@petrovitsch.priv.at
    LUGA : http://www.luga.at

    --
    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/

    \
     
     \ /
      Last update: 2010-04-18 13:07    [W:0.024 / U:29.236 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site