On Wed, 23 May 2012, Pantelis Antoniou wrote: > On May 23, 2012, at 6:11 PM, Alan Stern wrote: > > > On Thu, 24 May 2012, Pantelis Antoniou wrote: > > > >> OS-X uses a sequence on unmounting that makes us close the backing > >> file. > > > > What do you mean? Does OS-X send an eject command (as far as I know, > > that's the only command that will cause the backing file to be closed)? > > > > OS-X does sent an eject command. Okay. It has every right to do so. > >> Apparently there's no way to open it again, which makes it > >> impossible to remount without rmmod'ing g_mass_storage. > > > > That's not true at all. If the backing file has been closed, it can be > > re-opened (or another file can be opened in its place) by writing the > > filename to the gadget's "file" attribute in sysfs. > > > > Arguably that's not what you want, nor you expect. > > Linux doesn't sent the eject command so when you reconnect the cable the > original configuration (i.e. the old mass storage file) is used. > > Without this you need to either rmmod, or rewrite the filename to the gadget's > "file" attribute whenever the host umounts sending an eject command. > > So what we have is this: > > Linux host unmounts, backing file is not closed, disk will appear when > another mount command is issued, without having to write the "file" > attribute in sysfs. > > Mac OS X host unmounts, backing file is closed, disk will not appear > since no mount command can be issued, because the backing file is closed. > Only if the gadget's "file" attribute in sysfs is written, or module is > rmmod'ed & insmod'ed again will a mount command work. Yes, that all sounds right. > I'm open to suggestions that will make OS X behave in the same manner as > Linux. Then may I suggest that you write to the developers at Apple and send them your advice? Clearly nothing we do here in the linux-usb mailing list will change OS-X's behavior. :-) Seriously, if the host OS sends an eject command then we have to assume that this is what the user really wants. Suppose that instead of a mass-storage gadget, an actual USB storage device had been plugged in, like one of the old ZIP drives. When OS-X sends it an eject command, it will eject its cartridge. After that, no mount command will work until the user puts a new cartridge in the drive. That's exactly how the mass-storage gadget behaves. Of course, you always have the option of not specifying the "removable=y" module parameter when loading the gadget originally. Without that parameter, the backing file won't get closed when the eject command is received. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
