Many low-level drivers in Linux kernel register their serial ports with the help of universal driver (8250_core, 8250_port). There is an attribute group called `serial8250_dev_attr_group` within `8250_port.c` to handle the `rx_trig_bytes` attribute: https://lore.kernel.org/all/20140716011931.31474.68825.stgit@yuno-kbuild.novalocal/ However, if a low-level driver has some HW specifications that need to be set or retrieved using an attr_group, the universal driver (8250_port) would overwrite the low-level driver's attr_group. This patch allows the low-level driver's attr_group to be passed to the universal driver (8250_port) and combines the two attr_groups. This ensures that the corresponding system file will only be created if the device is registered by such a low-level driver. Signed-off-by: CrescentCY Hsieh <crescentcy.hsieh@xxxxxxxx> --- drivers/tty/serial/8250/8250_core.c | 9 +++++++++ drivers/tty/serial/8250/8250_port.c | 26 ++++++++++++++++++++++++-- include/linux/serial_core.h | 1 + 3 files changed, 34 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 43824a174a51..01d04f9d5192 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1130,6 +1130,8 @@ int serial8250_register_8250_port(const struct uart_8250_port *up) uart->port.pm = up->port.pm; if (up->port.handle_break) uart->port.handle_break = up->port.handle_break; + if (up->port.attr_group) + uart->port.attr_group = up->port.attr_group; if (up->dl_read) uart->dl_read = up->dl_read; if (up->dl_write) @@ -1210,6 +1212,13 @@ void serial8250_unregister_port(int line) uart->port.type = PORT_UNKNOWN; uart->port.dev = &serial8250_isa_devs->dev; uart->port.port_id = line; + + if (uart->port.attr_group_allocated) { + kfree(uart->port.attr_group->attrs); + kfree(uart->port.attr_group); + uart->port.attr_group_allocated = false; + } + uart->port.attr_group = NULL; uart->capabilities = 0; serial8250_init_port(uart); serial8250_apply_quirks(uart); diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 893bc493f662..ddfa8b59e562 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3135,9 +3135,31 @@ static struct attribute_group serial8250_dev_attr_group = { static void register_dev_spec_attr_grp(struct uart_8250_port *up) { const struct serial8250_config *conf_type = &uart_config[up->port.type]; + struct attribute **upp_attrs = NULL; + int upp_attrs_num = 0, i; - if (conf_type->rxtrig_bytes[0]) - up->port.attr_group = &serial8250_dev_attr_group; + up->port.attr_group_allocated = false; + + if (up->port.attr_group) { + upp_attrs = up->port.attr_group->attrs; + + while (upp_attrs[upp_attrs_num]) + upp_attrs_num++; + + up->port.attr_group = kcalloc(1, sizeof(struct attribute_group), GFP_KERNEL); + up->port.attr_group->attrs = kcalloc(upp_attrs_num + 2, sizeof(struct attribute *), GFP_KERNEL); + + for (i = 0; i < upp_attrs_num; ++i) + up->port.attr_group->attrs[i] = upp_attrs[i]; + + if (conf_type->rxtrig_bytes[0]) + up->port.attr_group->attrs[upp_attrs_num] = &dev_attr_rx_trig_bytes.attr; + + up->port.attr_group_allocated = true; + } else { + if (conf_type->rxtrig_bytes[0]) + up->port.attr_group = &serial8250_dev_attr_group; + } } static void serial8250_config_port(struct uart_port *port, int flags) diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 8cb65f50e830..3212d64c32c6 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -581,6 +581,7 @@ struct uart_port { unsigned char console_reinit; const char *name; /* port name */ struct attribute_group *attr_group; /* port specific attributes */ + bool attr_group_allocated; /* whether attr_group is dynamic allocated */ const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ struct serial_rs485 rs485; struct serial_rs485 rs485_supported; /* Supported mask for serial_rs485 */ -- 2.34.1
