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| author | Sven Schnelle <svens@linux.ibm.com> | 2026-09-09 11:29:53 +0200 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2026-09-10 08:43:35 +0900 |
| commit | d22c3e0088e85be8131f7a9283f759cdbb20726d (patch) | |
| tree | 9668df2aa27b26f850d3ba5ba1287e443803675c /Documentation/driver-api/serial/driver.rst | |
| download | linux-stable-d22c3e0088e85be8131f7a9283f759cdbb20726d.tar.gz linux-stable-d22c3e0088e85be8131f7a9283f759cdbb20726d.zip | |
selftests/ftrace: Fix unique symbol check in kprobe_non_uniq_symbol.tcgrafted
The current regex also matches symbols in modules, which makes the
test fail on s390 where name_show is present only once in the kernel,
but also multiple times in modules:
000001b1401cdc20 t name_show
000001b0c05e6c40 t name_show [mdev]
000001b0c0495f30 t name_show [i2c_core]
Fix this by changing the regular expression to only match the function
name.
Link: https://lore.kernel.org/all/20260909092954.2200558-1-svens@linux.ibm.com/
Fixes: 03b80ff8023a ("selftests/ftrace: Add new test case which checks non unique symbol")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'Documentation/driver-api/serial/driver.rst')
| -rw-r--r-- | Documentation/driver-api/serial/driver.rst | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/driver-api/serial/driver.rst new file mode 100644 index 000000000..c1db6a1a6 --- /dev/null +++ b/Documentation/driver-api/serial/driver.rst @@ -0,0 +1,105 @@ +==================== +Low Level Serial API +==================== + + +This document is meant as a brief overview of some aspects of the new serial +driver. It is not complete, any questions you have should be directed to +<rmk@arm.linux.org.uk> + +The reference implementation is contained within amba-pl011.c. + + + +Low Level Serial Hardware Driver +-------------------------------- + +The low level serial hardware driver is responsible for supplying port +information (defined by uart_port) and a set of control methods (defined +by uart_ops) to the core serial driver. The low level driver is also +responsible for handling interrupts for the port, and providing any +console support. + + +Console Support +--------------- + +The serial core provides a few helper functions. This includes +decoding command line arguments (uart_parse_options()). + +There is also a helper function (uart_console_write()) which performs a +character by character write, translating newlines to CRLF sequences. +Driver writers are recommended to use this function rather than implementing +their own version. + + +Locking +------- + +It is the responsibility of the low level hardware driver to perform the +necessary locking using port->lock. There are some exceptions (which +are described in the struct uart_ops listing below.) + +There are two locks. A per-port spinlock, and an overall semaphore. + +From the core driver perspective, the port->lock locks the following +data:: + + port->mctrl + port->icount + port->state->xmit.head (circ_buf->head) + port->state->xmit.tail (circ_buf->tail) + +The low level driver is free to use this lock to provide any additional +locking. + +The port_sem semaphore is used to protect against ports being added/ +removed or reconfigured at inappropriate times. Since v2.6.27, this +semaphore has been the 'mutex' member of the tty_port struct, and +commonly referred to as the port mutex. + + +uart_ops +-------- + +.. kernel-doc:: include/linux/serial_core.h + :identifiers: uart_ops + +Other functions +--------------- + +.. kernel-doc:: drivers/tty/serial/serial_core.c + :identifiers: uart_update_timeout uart_get_baud_rate uart_get_divisor + uart_match_port uart_write_wakeup uart_register_driver + uart_unregister_driver uart_suspend_port uart_resume_port + uart_add_one_port uart_remove_one_port uart_console_write + uart_parse_earlycon uart_parse_options uart_set_options + uart_get_lsr_info uart_handle_dcd_change uart_handle_cts_change + uart_try_toggle_sysrq + +.. kernel-doc:: include/linux/serial_core.h + :identifiers: uart_port_tx_limited uart_port_tx + +Other notes +----------- + +It is intended some day to drop the 'unused' entries from uart_port, and +allow low level drivers to register their own individual uart_port's with +the core. This will allow drivers to use uart_port as a pointer to a +structure containing both the uart_port entry with their own extensions, +thus:: + + struct my_port { + struct uart_port port; + int my_stuff; + }; + +Modem control lines via GPIO +---------------------------- + +Some helpers are provided in order to set/get modem control lines via GPIO. + +.. kernel-doc:: drivers/tty/serial/serial_mctrl_gpio.c + :identifiers: mctrl_gpio_init mctrl_gpio_to_gpiod + mctrl_gpio_set mctrl_gpio_get mctrl_gpio_enable_ms + mctrl_gpio_disable_ms_sync mctrl_gpio_disable_ms_no_sync |
