[PATCH 2/8] tty: fix return value for unsupported ioctls

Johan Hovold
2021-04-07T09:53:08Z

Drivers should return -ENOTTY ("Inappropriate I/O control operation")
when an ioctl isn't supported, while -EINVAL is used for invalid
arguments.

Fix up the TIOCMGET, TIOCMSET and TIOCGICOUNT helpers which returned
-EINVAL when a tty driver did not implement the corresponding
operations.

Note that the TIOCMGET and TIOCMSET helpers predate git and do not get a
corresponding Fixes tag below.

Fixes: d281da7ff6f7 ("tty: Make tiocgicount a handler")
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/tty_io.c | 10 +++++-----
include/linux/tty_driver.h | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index ebcde1f96adb..7738514a15fe 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2529,14 +2529,14 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
* @p: pointer to result
*
* Obtain the modem status bits from the tty driver if the feature
- * is supported. Return -EINVAL if it is not available.
+ * is supported. Return -ENOTTY if it is not available.
*
* Locking: none (up to the driver)
*/

static int tty_tiocmget(struct tty_struct *tty, int __user *p)
{
- int retval = -EINVAL;
+ int retval = -ENOTTY;

if (tty->ops->tiocmget) {
retval = tty->ops->tiocmget(tty);
@@ -2554,7 +2554,7 @@ static int tty_tiocmget(struct tty_struct *tty, int __user *p)
* @p: pointer to desired bits
*
* Set the modem status bits from the tty driver if the feature
- * is supported. Return -EINVAL if it is not available.
+ * is supported. Return -ENOTTY if it is not available.
*
* Locking: none (up to the driver)
*/
@@ -2566,7 +2566,7 @@ static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
unsigned int set, clear, val;

if (tty->ops->tiocmset == NULL)
- return -EINVAL;
+ return -ENOTTY;

retval = get_user(val, p);
if (retval)
@@ -2606,7 +2606,7 @@ int tty_get_icount(struct tty_struct *tty,
if (tty->ops->get_icount)
return tty->ops->get_icount(tty, icount);
else
- return -EINVAL;
+ return -ENOTTY;
}
EXPORT_SYMBOL_GPL(tty_get_icount);

diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 61c3372d3f32..2f719b471d52 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -228,7 +228,7 @@
*
* Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
* structure to complete. This method is optional and will only be called
- * if provided (otherwise EINVAL will be returned).
+ * if provided (otherwise ENOTTY will be returned).
*/

#include <linux/export.h>
--
2.26.3