Re: [PATCH 1/3] serdev: ttyport: make use of tty_kopen_exclusive

From: Jiri Slaby
Date: Mon Aug 19 2024 - 06:42:27 EST


On 19. 08. 24, 12:19, Marco Felsch wrote:
Hi,

sorry for not replying earlier.

On 24-08-08, Jiri Slaby wrote:
On 07. 08. 24, 16:08, Marco Felsch wrote:
The purpose of serdev is to provide kernel drivers for particular serial
device, serdev-ttyport is no exception here. Make use of the
tty_kopen_exclusive() funciton to mark this tty device as kernel
internal device.

Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
---
drivers/tty/serdev/serdev-ttyport.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
index 3d7ae7fa5018..94c43d25ddbe 100644
--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -103,11 +103,14 @@ static int ttyport_write_room(struct serdev_controller *ctrl)
static int ttyport_open(struct serdev_controller *ctrl)
{
struct serport *serport = serdev_controller_get_drvdata(ctrl);
+ struct tty_driver *tty_drv = serport->tty_drv;
struct tty_struct *tty;
struct ktermios ktermios;
+ dev_t dev;
int ret;
- tty = tty_init_dev(serport->tty_drv, serport->tty_idx);
+ dev = MKDEV(tty_drv->major, tty_drv->minor_start + serport->tty_idx);
+ tty = tty_kopen_exclusive(dev);

I believe that the now added tty_lookup_driver() has negligible impact in
this anyway slow path, right?

Can you please elaborate a bit more? I don't see how the
tty_lookup_driver() is involved in the serdev-ctrl open path anyway.

It's called now in of tty_kopen_exclusive()->tty_kopen(). (tty_lookup_driver() is the major difference between the raw tty_init_dev() and tty_kopen_exclusive().)

--
js
suse labs