On Tue, 16 Jun 2015, Xuebing Wang wrote:
> Hi Alan and community,
>
> I am using mass storage kernel module of v4.0.1 for Freescale i.MX6SL
> for a commercial product. As this is commercial product, thus USB host
> compatibility is important.
>
> 1) It seems that Windows 7 host can *not* auto-mount if I pass
> parameters as below:
> modprobe g_mass_storage file=/dev/mmcblk0p4 iSerialNumber=abcdefgh nofua=1
Have you read this sentence from the USB Mass Storage Class Bulk-Only
Transport specification (section 4.1.1 Serial Number)?
The serial number shall contain at least 12 valid digits,
represented as a UNICODE string.
I don't know if Windows pays any attention to the length of the serial
number string, but it might. Also, take a look at section 4.1.2 Valid
Serial Number characters: It lists '0' - '9' and 'A' - 'F' but not 'a'
and certainly not 'g' or 'h'.
> 2) Windows 7 can auto-mount, if I pass pass parameters as below (with
> removable=1)
> modprobe g_mass_storage file=/dev/mmcblk0p4 iSerialNumber=abcdefgh
> nofua=1 removable=1
>
> But, there is a problem. If I eject the removable disk from Win7,
> disconnect USB cable, and re-connect the USB cable, the removable disk
> can NOT be auto-mounted on Win7.
Well, sure. The same thing happens with real USB storage devices.
For example, if you eject a CDROM from a USB CD player, the removable
CD can't be auto-mounted until you put a CDROM back into the player.
Unplugging and re-connecting the USB cable won't help.
> It seems this makes sense, because Documentation/usb/mass-storage.txt
> says below:
> ------
> If this option (removable=1) is set for a logical unit, gadget will
> accept an
> “eject” SCSI request (Start/Stop Unit). When it is sent, the
> backing file will be closed to simulate ejection and the logical
> unit will not be mountable by the host until a new backing file is
> specified by userspace on the device (see “sysfs entries”
> section).
> ------
>
> Would you please advise what is the best way to pass parameters to
> g_mass_storage considering host compatibility?
This has nothing to do with parameters. If you want the storage to be
auto-mounted, don't eject it! Use the "Safely remove hardware" button
in Windows instead.
Also, what happens if you specify a _valid_ serial number and leave out
the "removable=1" parameter?
Alan Stern
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