From: Daniel Starke <daniel.starke@xxxxxxxxxxx> n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516 The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to the newer 27.010 here. Chapter 6 describes the error recovery mode option which is based on I frames. The k parameter defines the maximum number of I frames that a DLC can have unacknowledged as described in chapter 5.7.4. The current n_gsm implementation does not support the error recovery mode option. However, the k parameter is also part of the parameter negotiation message as described in chapter 5.4.6.3.1. Chapter 5.7.4 also notes that the allowed value range for k is 1-7. That means a 0 is counted as invalid here. This means that the user needs to configure a valid value here even if the function itself is not supported. Otherwise, parameter negotiation may fail. Allow setting of k via ioctl in gsm_config(). Range checks are already included. Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> --- drivers/tty/n_gsm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) v1 -> v2: No changes. Link: https://lore.kernel.org/all/20230228062957.3150-2-daniel.starke@xxxxxxxxxxx/ diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 9d0e7701ffd4..5bbedfc36fd1 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -3276,8 +3276,8 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c) int need_close = 0; int need_restart = 0; - /* Stuff we don't support yet - UI or I frame transport, windowing */ - if ((c->adaption != 1 && c->adaption != 2) || c->k) + /* Stuff we don't support yet - UI or I frame transport */ + if (c->adaption != 1 && c->adaption != 2) return -EOPNOTSUPP; /* Check the MRU/MTU range looks sane */ if (c->mru < MIN_MTU || c->mtu < MIN_MTU) -- 2.34.1
