linux-kernel - [PATCH v2 1/2] tty: add retry capability to tty_init

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Message-Id: <20191121152239.28405-1-sudipm.mukherjee@gmail.com>
Date:   Thu, 21 Nov 2019 15:22:38 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH v2 1/2] tty: add retry capability to tty_init_dev()

Add a new function tty_init_dev_retry() which will have the capability
to return if 'tty->port' is not yet set and if we want to retry. There
is no change in behaviour if we do not want to retry and call
tty_init_dev().

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
---

v1 was a combined patch of this and the next 2/2 patch. Made them
separately now.

 drivers/tty/tty_io.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e3076ea01222..95d7abeca254 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1291,9 +1291,10 @@ static int tty_reopen(struct tty_struct *tty)
 }
 
 /**
- *	tty_init_dev		-	initialise a tty device
+ *	tty_init_dev_retry	-	initialise a tty device
  *	@driver: tty driver we are opening a device on
  *	@idx: device index
+ *	@retry: retry count if driver has not set tty->port yet
  *	@ret_tty: returned tty structure
  *
  *	Prepare a tty device. This may not be a "new" clean device but
@@ -1314,7 +1315,8 @@ static int tty_reopen(struct tty_struct *tty)
  * relaxed for the (most common) case of reopening a tty.
  */
 
-struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
+static struct tty_struct *tty_init_dev_retry(struct tty_driver *driver,
+					     int idx, int retry)
 {
 	struct tty_struct *tty;
 	int retval;
@@ -1343,6 +1345,10 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 
 	if (!tty->port)
 		tty->port = driver->ports[idx];
+	if (!tty->port && retry) {
+		retval = -EAGAIN;
+		goto err_release_driver;
+	}
 
 	WARN_RATELIMIT(!tty->port,
 			"%s: %s driver does not set tty->port. This will crash the kernel later. Fix the driver!\n",
@@ -1365,6 +1371,8 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 	/* Return the tty locked so that it cannot vanish under the caller */
 	return tty;
 
+err_release_driver:
+	tty_driver_remove_tty(driver, tty);
 err_free_tty:
 	tty_unlock(tty);
 	free_tty_struct(tty);
@@ -1384,6 +1392,19 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 }
 
 /**
+ *	tty_init_dev		-	initialise a tty device
+ *	@driver: tty driver we are opening a device on
+ *	@idx: device index
+ *	@ret_tty: returned tty structure
+ *
+ *	Calls tty_init_dev_retry() with retry count of 0.
+ */
+struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
+{
+	return tty_init_dev_retry(driver, idx, 0);
+}
+
+/**
  * tty_save_termios() - save tty termios data in driver table
  * @tty: tty whose termios data to save
  *
-- 
2.11.0