Messages in this thread | | | Date | Fri, 7 Jan 2005 15:00:35 +0100 | From | Andries Brouwer <> | Subject | Re: [PATCH] MMC block removable flag |
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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.
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