[PATCH v2 03/31] tty: caif: do not use N_TTY_BUF_SIZE

[PATCH v2 03/31] tty: caif: do not use N_TTY_BUF_SIZE

[Jiri Slaby (SUSE)]

N_TTY_BUF_SIZE -- as the name suggests -- is the N_TTY's buffer size.
There is no reason to couple that to caif's tty->receive_room. Use 4096
directly -- even though, it should be some sort of "SKB_MAX_ALLOC" or
alike. But definitely not N_TTY_BUF_SIZE.

N_TTY_BUF_SIZE is private and will be moved to n_tty.c later.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: netdev@vger.kernel.org
---
 drivers/net/caif/caif_serial.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index ed3a589def6b..e7d1b9301fde 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -344,7 +344,7 @@ static int ldisc_open(struct tty_struct *tty)
 	ser->tty = tty_kref_get(tty);
 	ser->dev = dev;
 	debugfs_init(ser, tty);
-	tty->receive_room = N_TTY_BUF_SIZE;
+	tty->receive_room = 4096;
 	tty->disc_data = ser;
 	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 	rtnl_lock();
-- 
2.49.0

Re: [PATCH v2 00/31] tty: cleanup no. 99

[Jiri Slaby]

Cc (sorry):
Alex Elder <elder@kernel.org>
Andrew Lunn <andrew+netdev@lunn.ch>
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
David Lin <dtwlin@gmail.com>
"David S. Miller" <davem@davemloft.net>
Eric Dumazet <edumazet@google.com>
greybus-dev@lists.linaro.org
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Jakub Kicinski <kuba@kernel.org>
Johan Hovold <johan@kernel.org>
linux-alpha@vger.kernel.org
linux-mmc@vger.kernel.org
linux-staging@lists.linux.dev
Matt Turner <mattst88@gmail.com>
netdev@vger.kernel.org
Paolo Abeni <pabeni@redhat.com>
Richard Henderson <richard.henderson@linaro.org>
Rob Herring <robh@kernel.org>
sparclinux@vger.kernel.org
Ulf Hansson <ulf.hansson@linaro.org>

On 17. 03. 25, 8:00, Jiri Slaby (SUSE) wrote:
> Hi,
> 
> this is (again) a series of cleanup in tty. I am trying to rework
> tty+serial to avoid limitations of devices (so called NR_UART or
> tty_alloc_driver()'s first parameter). And the below popped up while
> crawling through the code. So this is only a prep cleanup.
> 
> * many tty flags are now enums
> * many functions were improved for readability
> * quite a few unused or old code dropped
> 
> In particular, the runtime behaviour of the kernel before and after the
> changes is supposed to be bug to bug compatible (except moxa's ioctl
> and ISA evils dropped). That is, noone should notice.
> 
> [v2]
>   * use serial_port_in/out() helpers in 26/30 (and not use serial_in/out())
>   * the last patch is new
> 
> Jiri Slaby (SUSE) (31):
>    tty: convert "TTY Struct Flags" to an enum
>    tty: audit: do not use N_TTY_BUF_SIZE
>    tty: caif: do not use N_TTY_BUF_SIZE
>    tty: move N_TTY_BUF_SIZE to n_tty
>    tty: n_tty: use uint for space returned by tty_write_room()
>    tty: n_tty: simplify process_output()
>    tty: n_tty: clean up process_output_block()
>    tty: n_tty: drop n_tty_trace()
>    tty: n_tty: extract n_tty_continue_cookie() from n_tty_read()
>    tty: n_tty: extract n_tty_wait_for_input()
>    tty: n_tty: move more_to_be_read to the end of n_tty_read()
>    tty: tty_driver: move TTY macros to the top
>    tty: tty_driver: convert "TTY Driver Flags" to an enum
>    tty: tty_driver: document both {,__}tty_alloc_driver() properly
>    tty: tty_driver: introduce TTY driver sub/types enums
>    tty: serdev: drop serdev_controller_ops::write_room()
>    tty: mmc: sdio: use bool for cts and remove parentheses
>    tty: moxa: drop version dump to logs
>    tty: moxa: drop ISA support
>    tty: moxa: carve out special ioctls and extra tty_port
>    tty: srmcons: fix retval from srmcons_init()
>    tty: staging/greybus: pass tty_driver flags to tty_alloc_driver()
>    tty: sunsu: drop serial_{in,out}p()
>    tty: sunsu: remove unused serial_icr_read()
>    serial: remove redundant tty_port_link_device()
>    serial: pass struct uart_state to uart_line_info()
>    serial: 8250: use serial_port_in/out() helpers
>    serial: 8250_rsa: simplify rsa8250_{request/release}_resource()
>    serial: 8250_port: do not use goto for UPQ_NO_TXEN_TEST code flow
>    serial: 8250_port: simplify serial8250_request_std_resource()
>    serial: switch change_irq and change_port to bool in uart_set_info()
> 
>   Documentation/driver-api/tty/tty_driver.rst |   4 +-
>   Documentation/driver-api/tty/tty_struct.rst |   2 +-
>   arch/alpha/kernel/srmcons.c                 |  62 ++---
>   drivers/mmc/core/sdio_uart.c                |   2 +-
>   drivers/net/caif/caif_serial.c              |   2 +-
>   drivers/staging/greybus/uart.c              |   4 +-
>   drivers/tty/Kconfig                         |   2 +-
>   drivers/tty/moxa.c                          | 251 +-------------------
>   drivers/tty/n_tty.c                         | 212 ++++++++---------
>   drivers/tty/serdev/core.c                   |  11 -
>   drivers/tty/serdev/serdev-ttyport.c         |   9 -
>   drivers/tty/serial/8250/8250_dw.c           |  16 +-
>   drivers/tty/serial/8250/8250_fsl.c          |   8 +-
>   drivers/tty/serial/8250/8250_omap.c         |   2 +-
>   drivers/tty/serial/8250/8250_port.c         |  59 ++---
>   drivers/tty/serial/8250/8250_rsa.c          |  21 +-
>   drivers/tty/serial/serial_core.c            |  10 +-
>   drivers/tty/serial/sunsu.c                  | 178 ++++++--------
>   drivers/tty/tty_audit.c                     |  10 +-
>   drivers/tty/tty_io.c                        |   8 +-
>   include/linux/serdev.h                      |   6 -
>   include/linux/tty.h                         |  53 +++--
>   include/linux/tty_driver.h                  | 180 +++++++-------
>   23 files changed, 412 insertions(+), 700 deletions(-)
> 


-- 
js
suse labs

Re: [PATCH v2 03/31] tty: caif: do not use N_TTY_BUF_SIZE

[Simon Horman]

On Mon, Mar 17, 2025 at 08:00:18AM +0100, Jiri Slaby (SUSE) wrote:
> N_TTY_BUF_SIZE -- as the name suggests -- is the N_TTY's buffer size.
> There is no reason to couple that to caif's tty->receive_room. Use 4096
> directly -- even though, it should be some sort of "SKB_MAX_ALLOC" or
> alike. But definitely not N_TTY_BUF_SIZE.

Hi Jiri,

My 2c worth is that 4096 seems like an arbitrary value.
Which is fine, but perhaps a comment is warranted.

> 
> N_TTY_BUF_SIZE is private and will be moved to n_tty.c later.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
> Acked-by: Jakub Kicinski <kuba@kernel.org>
> Cc: Andrew Lunn <andrew+netdev@lunn.ch>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: netdev@vger.kernel.org
> ---
>  drivers/net/caif/caif_serial.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
> index ed3a589def6b..e7d1b9301fde 100644
> --- a/drivers/net/caif/caif_serial.c
> +++ b/drivers/net/caif/caif_serial.c
> @@ -344,7 +344,7 @@ static int ldisc_open(struct tty_struct *tty)
>  	ser->tty = tty_kref_get(tty);
>  	ser->dev = dev;
>  	debugfs_init(ser, tty);
> -	tty->receive_room = N_TTY_BUF_SIZE;
> +	tty->receive_room = 4096;
>  	tty->disc_data = ser;
>  	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
>  	rtnl_lock();
> -- 
> 2.49.0
> 
>