From: Kay Sievers <kay.sievers@vrfy.org>
To: linux-hotplug@vger.kernel.org
Subject: Re: USB card reader media detection
Date: Fri, 01 Apr 2005 14:40:11 +0000 [thread overview]
Message-ID: <1112366412.5681.16.camel@localhost.localdomain> (raw)
In-Reply-To: <000701c536af$9e5e8b20$f601a8c0@SenatorPalmer>
On Fri, 2005-04-01 at 12:40 +0100, Andrew Marshall wrote:
> I am currently running version 2.4.22 of the Kernel and am writing an
> application that needs to cope with the removal of card media form a USB
> flash card reader.
> I have found that the block device file (part1) corresponding to my flash
> card's partition is appropriately updated (i.e removed from
> /dev/scsi/host0/bus0/target0/lun0/ when the test card is removed) -- but
> only if the partition is *not* currently mounted!
I don't remember the old 2.4 kernels, but I can't imagine how the kernel
could detect this.
> I found that once I have mounted the partition, the devfs 'part1' block
> device perpetually remains -- even when the card is removed, thus making
> removal detection a tad tricky.
>
> OK, it seems to be possible to unmount the partition, poll the
> /dev/scsi/host0/bus0/target0/lun0 entry and then remount once the poller has
> determined that the partition is still present -- but this takes time... And
> also seems a little extreme (if not ridiculous)...
Just poll continuously the main block device, which causes a re-read of
the partition table with every open(). There is no other way to do that.
Card-readers don't tell the kernel, if a media change happened.
Kay
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next prev parent reply other threads:[~2005-04-01 14:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-01 11:40 USB card reader media detection Andrew Marshall
2005-04-01 14:40 ` Kay Sievers [this message]
2005-04-05 17:51 ` Greg KH
2005-04-06 11:06 ` Andrew Marshall
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