[Buildroot] package/hotplug

[Buildroot] package/hotplug

[H Hartley Sweeten]

Hello all,

I am trying to get USB memory stick hotplugging to work on my busybox system.  I
would like to be able to attach a memory stick and have the system auto mount the
drive.

I assumed that I would need to enable hotplug package to do this but it is normally
disabled by BR2_PACKAGE_BUSYBOX_SHOW_OTHERS.  I have looked thru the busybox
configuration and can't find anything that would replace the hotplug app.  Did I
overlook something?

Regards,
Hartley

[Buildroot] package/hotplug

[Will Newton]

On Thu, Aug 19, 2010 at 1:43 AM, H Hartley Sweeten
<hartleys@visionengravers.com> wrote:
> Hello all,
>
> I am trying to get USB memory stick hotplugging to work on my busybox system. ?I
> would like to be able to attach a memory stick and have the system auto mount the
> drive.
>
> I assumed that I would need to enable hotplug package to do this but it is normally
> disabled by BR2_PACKAGE_BUSYBOX_SHOW_OTHERS. ?I have looked thru the busybox
> configuration and can't find anything that would replace the hotplug app. ?Did I
> overlook something?

mdev from busybox should do what you need. You'll need a line like
this in your inittab:

::sysinit:/bin/echo /sbin/mdev > /proc/sys/kernel/hotplug

It's not as flexible as udev, but should do what you need.

[Buildroot] package/hotplug

[H Hartley Sweeten]

On Thursday, August 19, 2010 2:26 AM, Will Newton wrote:
> On Thu, Aug 19, 2010 at 1:43 AM, H Hartley Sweeten wrote:
>> Hello all,
>>
>> I am trying to get USB memory stick hotplugging to work on my busybox
>> system. ?I would like to be able to attach a memory stick and have the
>> system auto mount the drive.
>>
>> I assumed that I would need to enable hotplug package to do this but
>> it is normally disabled by BR2_PACKAGE_BUSYBOX_SHOW_OTHERS. ?I have
>> looked thru the busybox configuration and can't find anything that
>> would replace the hotplug app. ?Did I overlook something?
>
> mdev from busybox should do what you need. You'll need a line like
> this in your inittab:
>
> ::sysinit:/bin/echo /sbin/mdev > /proc/sys/kernel/hotplug
>
> It's not as flexible as udev, but should do what you need.

Hello Will, thanks for the reply.

I have already tried 'echo /sbin/mdev > /proc/sys/kernel/hotplug' from
a command line.  When I insert the USB memory stick it is detected but
not mounted (same result without the command above).

I just tried adding the line above to my inittab and I get the same
result.

usb 2-1.4: new high speed USB device using fsl-ehci and address 4
usb 2-1.4: configuration #1 chosen from 1 choice
scsi0 : SCSI emulation for USB Mass Storage devices
scsi 0:0:0:0: Direct-Access     USB      Flash Disk       4.00 PQ: 0 ANSI: 2
sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
sd 0:0:0:0: [sda] Assuming drive cache: write through
 sda:
sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] Attached SCSI removable disk

My buildroot setup is pretty much a generic arm config.  This config
uses the device table from target/generic/device_table.txt so the
/dev/sda nodes actually exist even before the USB memory stick is
connected.  I assume mdev would create them if then were not there.

I can mount the drive manually:

# cat /proc/partitions  | grep sda
   8        0     998142 sda
# ls /mnt
# mount -t vfat /dev/sda /mnt
# ls /mnt
test_file.txt
# mount | grep sda
/dev/sda on /mnt type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1,errors=remount-ro)

But, how to I get mdev to mount the drive after it's detected?

Regards,
Hartley

[Buildroot] package/hotplug

[Will Newton]

On Thu, Aug 19, 2010 at 6:10 PM, H Hartley Sweeten
<hartleys@visionengravers.com> wrote:

> I have already tried 'echo /sbin/mdev > /proc/sys/kernel/hotplug' from
> a command line. ?When I insert the USB memory stick it is detected but
> not mounted (same result without the command above).
>
> I just tried adding the line above to my inittab and I get the same
> result.
>
> usb 2-1.4: new high speed USB device using fsl-ehci and address 4
> usb 2-1.4: configuration #1 chosen from 1 choice
> scsi0 : SCSI emulation for USB Mass Storage devices
> scsi 0:0:0:0: Direct-Access ? ? USB ? ? ?Flash Disk ? ? ? 4.00 PQ: 0 ANSI: 2
> sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
> sd 0:0:0:0: [sda] Write Protect is off
> sd 0:0:0:0: [sda] Assuming drive cache: write through
> sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
> sd 0:0:0:0: [sda] Assuming drive cache: write through
> ?sda:
> sd 0:0:0:0: [sda] 499071 2048-byte logical blocks: (1.02 GB/974 MiB)
> sd 0:0:0:0: [sda] Assuming drive cache: write through
> sd 0:0:0:0: [sda] Attached SCSI removable disk
>
> My buildroot setup is pretty much a generic arm config. ?This config
> uses the device table from target/generic/device_table.txt so the
> /dev/sda nodes actually exist even before the USB memory stick is
> connected. ?I assume mdev would create them if then were not there.
>
> I can mount the drive manually:
>
> # cat /proc/partitions ?| grep sda
> ? 8 ? ? ? ?0 ? ? 998142 sda
> # ls /mnt
> # mount -t vfat /dev/sda /mnt
> # ls /mnt
> test_file.txt
> # mount | grep sda
> /dev/sda on /mnt type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1,errors=remount-ro)
>
> But, how to I get mdev to mount the drive after it's detected?

it may be possible with the mdev config file. It seems to only be
documented in the source:

http://git.busybox.net/busybox/tree/util-linux/mdev.c

See the section that mentions executing a command.

[Buildroot] package/hotplug

[H Hartley Sweeten]

On Thursday, August 19, 2010 10:58 AM, Will Newton wrote:
> On Thu, Aug 19, 2010 at 6:10 PM, H Hartley Sweeten wrote:
>> But, how to I get mdev to mount the drive after it's detected?
>
> it may be possible with the mdev config file. It seems to only be
> documented in the source:
>
> http://git.busybox.net/busybox/tree/util-linux/mdev.c
>
> See the section that mentions executing a command.

I figured it had something to do with the mdev.conf file.  I did
some grep'ing and found the KwikByte target handles this with a
custom '/sbin/automount.script' that is called by mdev.

I have modified my setup and it appears to be working.  When I plug
in the USB drive it is now detected and mounted.  The only issue I
have now is when the drive is removed.  mdev does call the script
to unmount the drive but I get two kernel errors:

usb 2-1.4: USB disconnect, address 4
FAT: bread failed in fat_clusters_flush
FAT: bread failed in fat_clusters_flush

I think these are generated because the drive is actually not present
when umount tries to unmount it.  I'm using the -f option (force unmount)
but that doesn't seem to prevent the error.

Thanks for the help,
Hartley

[Buildroot] package/hotplug

[Michael S. Zick]

On Thu August 19 2010, H Hartley Sweeten wrote:
> On Thursday, August 19, 2010 10:58 AM, Will Newton wrote:
> > On Thu, Aug 19, 2010 at 6:10 PM, H Hartley Sweeten wrote:
> >> But, how to I get mdev to mount the drive after it's detected?
> >
> > it may be possible with the mdev config file. It seems to only be
> > documented in the source:
> >
> > http://git.busybox.net/busybox/tree/util-linux/mdev.c
> >
> > See the section that mentions executing a command.
> 
> I figured it had something to do with the mdev.conf file.  I did
> some grep'ing and found the KwikByte target handles this with a
> custom '/sbin/automount.script' that is called by mdev.
> 
> I have modified my setup and it appears to be working.  When I plug
> in the USB drive it is now detected and mounted.  The only issue I
> have now is when the drive is removed.  mdev does call the script
> to unmount the drive but I get two kernel errors:
> 
> usb 2-1.4: USB disconnect, address 4
> FAT: bread failed in fat_clusters_flush
> FAT: bread failed in fat_clusters_flush
> 
> I think these are generated because the drive is actually not present
> when umount tries to unmount it.  I'm using the -f option (force unmount)
> but that doesn't seem to prevent the error.
> 

It can't, the drive isn't there to write to once you remove it.

Add a "safely unmount" thingy to whatever interface your device has, 
call a:
mount -o remount device_name
script.
Note there is no option specified after the "remount" - not a typo here.
That will make the kernel flush its VFS buffers for that device.

Mike
> Thanks for the help,
> Hartley
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
> 
> 

[Buildroot] package/hotplug

[Mitch Davis]

Hartley,

On Fri, Aug 20, 2010 at 4:59 AM, Michael S. Zick <minimod@morethan.org> wrote:
> On Thu August 19 2010, H Hartley Sweeten wrote:
>> On Thursday, August 19, 2010 10:58 AM, Will Newton wrote:
>> > On Thu, Aug 19, 2010 at 6:10 PM, H Hartley Sweeten wrote:
>> >> But, how to I get mdev to mount the drive after it's detected?
>> >
>> > it may be possible with the mdev config file. It seems to only be
>> > documented in the source:
>> >
>> > http://git.busybox.net/busybox/tree/util-linux/mdev.c
>> >
>> > See the section that mentions executing a command.
>>
>> I figured it had something to do with the mdev.conf file. ?I did
>> some grep'ing and found the KwikByte target handles this with a
>> custom '/sbin/automount.script' that is called by mdev.
>>
>> I have modified my setup and it appears to be working. ?When I plug
>> in the USB drive it is now detected and mounted. ?The only issue I
>> have now is when the drive is removed. ?mdev does call the script
>> to unmount the drive but I get two kernel errors:
>>
>> usb 2-1.4: USB disconnect, address 4
>> FAT: bread failed in fat_clusters_flush
>> FAT: bread failed in fat_clusters_flush
>>
>> I think these are generated because the drive is actually not present
>> when umount tries to unmount it. ?I'm using the -f option (force unmount)
>> but that doesn't seem to prevent the error.
>
> It can't, the drive isn't there to write to once you remove it.
>
> Add a "safely unmount" thingy to whatever interface your device has,
> call a:
> mount -o remount device_name
> script.
> Note there is no option specified after the "remount" - not a typo here.
> That will make the kernel flush its VFS buffers for that device.

If you don't need to write to the device, you could also use "mount -o
ro" to make it read-only.  Then you won't get the message.  If it
happens that you need to write, you can temporarily call "mount -o
remount,rw", do your op, then "mount -o remount,ro".

Alternatively (and this is a little bit gross), if you don't want the
kernel to do any mounting, you may be able to hack "mtools" to use it
as a library:

  http://www.gnu.org/software/mtools/

Then the kernel wouldn't care if the device was pulled unexpectedly.

Mitch.