Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszer...

[karo-tx-linux.git] / Documentation / serial / n_gsm.txt

diff --git a/Documentation/serial/n_gsm.txt b/Documentation/serial/n_gsm.txt
index a5d91126a8f7110b4dd86b2286842127adc0ff4b..875361bb7cb4646d6edf5d47ccdb676c27dbbee5 100644 (file)
--- a/Documentation/serial/n_gsm.txt
+++ b/Documentation/serial/n_gsm.txt
@@ -77,6 +77,13 @@ for example, it's possible :
 
 6- first close all virtual ports before closing the physical port.
 
+Note that after closing the physical port the modem is still in multiplexing
+mode. This may prevent a successful re-opening of the port later. To avoid
+this situation either reset the modem if your hardware allows that or send
+a disconnect command frame manually before initializing the multiplexing mode
+for the second time. The byte sequence for the disconnect command frame is:
+0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9.
+
 Additional Documentation
 ------------------------
 More practical details on the protocol and how it's supported by industrial