diff options
| author | John Ogness <john.ogness@linutronix.de> | 2026-05-06 14:21:56 +0206 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-05-11 16:58:28 +0200 |
| commit | 9c7eb1c9c3e3bfecb556fc8fa1b68939385444de (patch) | |
| tree | ef356f615ad44305ae254345dc0bbdd4f521e363 /include | |
| parent | 430a1386df5c98e65f6b943c15366e4ca92e3328 (diff) | |
serial: core: Add dedicated uart_port field for console flow
Currently the UPF_CONS_FLOW bit in the uart_port.flags field is used
by serial console drivers to identify if a user has configured flow
control on the console. Usually this policy is setup during early
boot, but can be changed at runtime.
The bits in uart_port.flags are either hardware and driver
properties that are initialized before usage or are properties that
can be changed via the tty layer.
The UPF_CONS_FLOW bit is an exception because it is a console-only
policy that can change at runtime and its setting and usage have
nothing to do with the tty layer. This actually causes a problem
for its usage because uart_port.flags is synchronized by a related
tty_port.mutex, but a console has no relation to a tty (other than
sharing the port).
This is probably why console flow control is not properly available
for most serial drivers. And it is hindering being able to provide a
proper implementation. Commit d01f4d181c92 ("serial: core: Privatize
tty->hw_stopped") addressed a similar issue to deal with software
assisted CTS flow state tracking.
Add a new uart_port boolean field "cons_flow" to store the user
configuration for console flow control. Add getter/setter wrappers
to allow for adding more policies later and/or locking constraint
validation.
Mark UPF_CONS_FLOW as deprecated.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20260506121606.5805-2-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/serial_core.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 666430b47899..4f7bbdd90017 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -533,6 +533,7 @@ struct uart_port { #define UPF_HARD_FLOW ((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS)) /* Port has hardware-assisted s/w flow control */ #define UPF_SOFT_FLOW ((__force upf_t) BIT_ULL(22)) +/* Deprecated: use uart_set_cons_flow_enabled()/uart_cons_flow_enabled() instead. */ #define UPF_CONS_FLOW ((__force upf_t) BIT_ULL(23)) #define UPF_SHARE_IRQ ((__force upf_t) BIT_ULL(24)) #define UPF_EXAR_EFR ((__force upf_t) BIT_ULL(25)) @@ -567,6 +568,7 @@ struct uart_port { #define UPSTAT_SYNC_FIFO ((__force upstat_t) (1 << 5)) bool hw_stopped; /* sw-assisted CTS flow state */ + bool cons_flow; /* user specified console flow control */ unsigned int mctrl; /* current modem ctrl settings */ unsigned int frame_time; /* frame timing in ns */ unsigned int type; /* port type */ @@ -1163,6 +1165,16 @@ static inline bool uart_softcts_mode(struct uart_port *uport) return ((uport->status & mask) == UPSTAT_CTS_ENABLE); } +static inline void uart_set_cons_flow_enabled(struct uart_port *uport, bool enabled) +{ + uport->cons_flow = enabled; +} + +static inline bool uart_cons_flow_enabled(const struct uart_port *uport) +{ + return uport->cons_flow; +} + /* * The following are helper functions for the low level drivers. */ |