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    SubjectRe: [PATCH] MMC block removable flag
    On Fri, Jan 07, 2005 at 12:39:47PM +0000, Russell King wrote:
    > On Thu, Dec 30, 2004 at 04:56:45PM +0100, Pierre Ossman wrote:
    > > Russell King wrote:
    > > >On Thu, Dec 30, 2004 at 03:14:07AM +0100, Pierre Ossman wrote:
    > > >>A MMC card is a highly removable device. This patch makes the block
    > > >>layer part of the MMC layer set the removable flag.
    > > >
    > > >I have this patch also floating around, but I've decided it isn't needed.
    > > >I believe this flag is to indicate that we have removable media for a
    > > >block device rather than to indicate that the block device can be removed.
    > > >
    > > >However, when we insert and remove a MMC card, we create and destroy the
    > > >block device itself. Therefore, as far as the block layer is concerned,
    > > >the device itself is being inserted and removed, so telling the block
    > > >layer that the media is removable is just silly - you can't separate the
    > > >flash media from the on-board MMC controller.
    > > >
    > > >(Note: any block device can be removed - you just rmmod the module
    > > >supplying the block device driver, but this doesn't mean we mark all
    > > >block devices with GENHD_FL_REMOVABLE.)
    > >
    > > I suspect that the removable flag might be used in different GUI:s to
    > > figure out with block devices should be presented to the user in a nice
    > > way. It's usually just the removable devices that need some form of
    > > special handling. So even though, as you point out, the entire device
    > > disappears it might be useful from a user interface perspective to have
    > > this hint set. From what I've found this flag doesn't seem to change any
    > > handling inside the kernel, just how the device should be perceived.
    >
    > Can anyone comment on the purpose of this (GENHD_FL_REMOVABLE) flag?
    > Al? Jens?

    GENHD_FL_REMOVABLE is set by a number of drivers (floppy, CDROM, ...).
    It is used in two places:
    (1) to fill the file /sys/block/*/removable
    (2) in genhd to suppress listing a nonpartitioned removable device
    in /proc/partitions.

    In other words, it is for user space only, precisely as Pierre Ossman said.

    Andries
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