Date:	Wed, 19 Dec 2007 15:49:32 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Alan Stern" <stern@...land.harvard.edu>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, mdharm-usb@...-eyed-alien.net,
	gregkh@...e.de, linux-usb@...r.kernel.org,
	usb-storage@...ts.one-eyed-alien.net
Subject: Re: 2.6.24-rc5-mm1

On Dec 17, 2007 9:14 AM, Dave Young <hidave.darkstar@...il.com> wrote:
> On Dec 14, 2007 11:44 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> > On Fri, 14 Dec 2007, Dave Young wrote:
> >
> > > Hi,
> > > The behaviour of my mp3 player (also act as usb-storage device) seems
> > > changed from rc5 to rc5-mm1.
> >
> > This can't be considered a bug, right?
>
> I'm not sure.
>
>
> > It's just that the player
> > changed from one slightly non-standard behavior to a different slightly
> > non-standard behavior.
> >
> >
> > > <dmesg output under rc5>:
> > > =========
> > > usb 1-7: new high speed USB device using ehci_hcd and address 7
> > > usb 1-7: configuration #1 chosen from 1 choice
> > > scsi4 : SCSI emulation for USB Mass Storage devices
> > > usb-storage: device found at 7
> > > usb-storage: waiting for device to settle before scanning
> > > scsi 4:0:0:0: Direct-Access                   Newman mp3       PQ: 0 ANSI: 0 CCS
> > > sd 4:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 4:0:0:0: [sdb] Write Protect is on
> > > sd 4:0:0:0: [sdb] Mode Sense: 03 00 80 00
> > > sd 4:0:0:0: [sdb] Assuming drive cache: write through
> > > sd 4:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 4:0:0:0: [sdb] Write Protect is on
> > > sd 4:0:0:0: [sdb] Mode Sense: 03 00 80 00
> > > sd 4:0:0:0: [sdb] Assuming drive cache: write through
> > >  sdb: sdb1
> > > sd 4:0:0:0: [sdb] Attached SCSI removable disk
> > > sd 4:0:0:0: Attached scsi generic sg1 type 0
> > > usb-storage: device scan complete
> > >
> > > ==========
> > > try mount it (or just blockdev --rereadpt), then write protect become off:
> > > ==========
> > >
> > > sd 4:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 4:0:0:0: [sdb] Write Protect is off
> > > sd 4:0:0:0: [sdb] Mode Sense: 03 00 00 00
> > > sd 4:0:0:0: [sdb] Assuming drive cache: write through
> > > sd 4:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 4:0:0:0: [sdb] Write Protect is off
> > > sd 4:0:0:0: [sdb] Mode Sense: 03 00 00 00
> > > sd 4:0:0:0: [sdb] Assuming drive cache: write through
> > >  sdb: sdb1
> >
> > This output won't appear if you simply mount the device.  So how do you
> > know that mounting turns off write protect?
>
> This can be observed by eye:
> dmesg -> mount -> dmesg
>
> >
> > > But under rc5-mm1, after mount command being executed, it is just
> > > mouted as read only partition without set the write-protect to off
> > >
> > > I tried "blockdev --rereadpt", it do set the write-protect to off as rc5 kernel.
> > >
> > > Below is the output of dmesg under rc5-mm1
> > > ==========
> > > usb 1-8: new high speed USB device using ehci_hcd and address 6
> > > usb 1-8: configuration #1 chosen from 1 choice
> > > scsi3 : SCSI emulation for USB Mass Storage devices
> > > usb-storage: device found at 6
> > > usb-storage: waiting for device to settle before scanning
> > > scsi 3:0:0:0: Direct-Access                   Newman mp3       PQ: 0 ANSI: 0 CCS
> > > sd 3:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 3:0:0:0: [sdb] Write Protect is on
> > > sd 3:0:0:0: [sdb] Mode Sense: 03 00 80 00
> > > sd 3:0:0:0: [sdb] Assuming drive cache: write through
> > > sd 3:0:0:0: [sdb] 245248 512-byte hardware sectors (126 MB)
> > > sd 3:0:0:0: [sdb] Write Protect is on
> > > sd 3:0:0:0: [sdb] Mode Sense: 03 00 80 00
> > > sd 3:0:0:0: [sdb] Assuming drive cache: write through
> > >  sdb: sdb1
> >
> > This looks exactly the same as the output above (except for various
> > port, device, and bus numbers).
>
> Yes, but lacks the part of "'Write Protect if off'  and other lines".
>
> >
> > If you turn on CONFIG_USB_STORAGE_DEBUG for both kernels and compare
> > the dmesg output for the mount command, that might highlight the
> > difference.
>
> Ok, I will test with do once have time, thanks.
>

There's not useful infomation with DEBUG on.

I tested on another machine with kernel 2.6.24-rc2. And the result is
diffrent again.
Here is the result:

1. on 2.6.24-rc2, when I plugin the player the kernel reports below messages:

usb-storage: waiting for device to settle before scanning
/*[lets mark the below part as part 1]*/
scsi 0:0:0:0: Direct-Access                   Newman mp3       PQ: 0 ANSI: 0 CCS
sd 0:0:0:0: [sda] 245248 512-byte hardware sectors (126 MB)
sd 0:0:0:0: [sda] Write Protect is on
sd 0:0:0:0: [sda] Mode Sense: 03 00 80 00
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] 245248 512-byte hardware sectors (126 MB)
sd 0:0:0:0: [sda] Write Protect is on
sd 0:0:0:0: [sda] Mode Sense: 03 00 80 00
sd 0:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1
/*[lets mark the below part as part 2]*/
sd 0:0:0:0: [sda] Attached SCSI removable disk
usb-storage: device scan complete
sd 0:0:0:0: [sda] 245248 512-byte hardware sectors (126 MB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Mode Sense: 03 00 00 00
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] 245248 512-byte hardware sectors (126 MB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Mode Sense: 03 00 00 00
sd 0:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1

2. on 2.6.24-rc5 kernel reports only the part 1, after try mount the
disk it reports the part 2 and mount the partition as rw

3. on 2.6.24-rc5 kernel reports only the part 1, after try mount the
disk it just mount the partition as ro with nothing more messages.

Regards
dave
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