USB: gadget: g_serial: append zlp when tx buffer becomes empty
USB: gadget: g_serial: append zlp when tx buffer becomes empty

Some usb serial host drivers expect a short packet before they forward
the data to the application. This is caused by them trying to read more
than one packet at a time. So when the gadget sends an exact multiple
of the maximum packet size, it should append a zero-length packet.

Signed-off-by: Daniel Glöckner <9334386da73fed86a833aadf1e01e2ce4e4273e5@emlix.com>
Cc: David Brownell <a0d09457d62acbdeb1fae1223575100ccbfffdf9@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@suse.de>


KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs