[PATCH v3 12/15] drivers: net: slip: remove SLIP_MAGIC

From: Ahelenia Ziemiańska
Date: Thu Nov 10 2022 - 20:16:11 EST

According to Greg, in the context of magic numbers as defined in
magic-number.rst, "the tty layer should not need this and I'll gladly
take patches".

We have largely moved away from this approach, and we have better
debugging instrumentation nowadays: kill it.

Additionally, all SLIP_MAGIC checks just early-exit instead of noting
the bug, so they're detrimental, if anything.

Link: https://lore.kernel.org/linux-doc/YyMlovoskUcHLEb7@xxxxxxxxx/
Reviewed-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Acked-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
Documentation/process/magic-number.rst | 1 -
.../translations/it_IT/process/magic-number.rst | 1 -
.../translations/zh_CN/process/magic-number.rst | 1 -
.../translations/zh_TW/process/magic-number.rst | 1 -
drivers/net/slip/slip.c | 11 +++++------
drivers/net/slip/slip.h | 4 ----
6 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/Documentation/process/magic-number.rst b/Documentation/process/magic-number.rst
index 3b3e607e1cbc..e59c707ec785 100644
--- a/Documentation/process/magic-number.rst
+++ b/Documentation/process/magic-number.rst
@@ -69,6 +69,5 @@ Changelog::
Magic Name Number Structure File
===================== ================ ======================== ==========================================
FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
-SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
===================== ================ ======================== ==========================================
diff --git a/Documentation/translations/it_IT/process/magic-number.rst b/Documentation/translations/it_IT/process/magic-number.rst
index e8c659b6a743..37a539867b6f 100644
--- a/Documentation/translations/it_IT/process/magic-number.rst
+++ b/Documentation/translations/it_IT/process/magic-number.rst
@@ -75,6 +75,5 @@ Registro dei cambiamenti::
Nome magico Numero Struttura File
===================== ================ ======================== ==========================================
FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
-SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
===================== ================ ======================== ==========================================
diff --git a/Documentation/translations/zh_CN/process/magic-number.rst b/Documentation/translations/zh_CN/process/magic-number.rst
index 2105af32187c..8a3a3e872c52 100644
--- a/Documentation/translations/zh_CN/process/magic-number.rst
+++ b/Documentation/translations/zh_CN/process/magic-number.rst
@@ -58,6 +58,5 @@ Linux 魔术数
魔术数名 数字 结构 文件
===================== ================ ======================== ==========================================
FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
-SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
===================== ================ ======================== ==========================================
diff --git a/Documentation/translations/zh_TW/process/magic-number.rst b/Documentation/translations/zh_TW/process/magic-number.rst
index 793a0ae9fb7c..7ace7834f7f9 100644
--- a/Documentation/translations/zh_TW/process/magic-number.rst
+++ b/Documentation/translations/zh_TW/process/magic-number.rst
@@ -61,6 +61,5 @@ Linux 魔術數
魔術數名 數字 結構 文件
===================== ================ ======================== ==========================================
FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
-SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
===================== ================ ======================== ==========================================
diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index 6865d32270e5..95f5c79772e7 100644
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -426,7 +426,7 @@ static void slip_transmit(struct work_struct *work)

spin_lock_bh(&sl->lock);
/* First make sure we're connected. */
- if (!sl->tty || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) {
+ if (!sl->tty || !netif_running(sl->dev)) {
spin_unlock_bh(&sl->lock);
return;
}
@@ -690,7 +690,7 @@ static void slip_receive_buf(struct tty_struct *tty, const unsigned char *cp,
{
struct slip *sl = tty->disc_data;

- if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev))
+ if (!sl || !netif_running(sl->dev))
return;

/* Read the characters out of the buffer */
@@ -761,7 +761,6 @@ static struct slip *sl_alloc(void)
sl = netdev_priv(dev);

/* Initialize channel control data */
- sl->magic = SLIP_MAGIC;
sl->dev = dev;
spin_lock_init(&sl->lock);
INIT_WORK(&sl->tx_work, slip_transmit);
@@ -809,7 +808,7 @@ static int slip_open(struct tty_struct *tty)

err = -EEXIST;
/* First make sure we're not already connected. */
- if (sl && sl->magic == SLIP_MAGIC)
+ if (sl)
goto err_exit;

/* OK. Find a free SLIP channel to use. */
@@ -886,7 +885,7 @@ static void slip_close(struct tty_struct *tty)
struct slip *sl = tty->disc_data;

/* First make sure we're connected. */
- if (!sl || sl->magic != SLIP_MAGIC || sl->tty != tty)
+ if (!sl || sl->tty != tty)
return;

spin_lock_bh(&sl->lock);
@@ -1080,7 +1079,7 @@ static int slip_ioctl(struct tty_struct *tty, unsigned int cmd,
int __user *p = (int __user *)arg;

/* First make sure we're connected. */
- if (!sl || sl->magic != SLIP_MAGIC)
+ if (!sl)
return -EINVAL;

switch (cmd) {
diff --git a/drivers/net/slip/slip.h b/drivers/net/slip/slip.h
index 3d7f88b330c1..d7dbedd27669 100644
--- a/drivers/net/slip/slip.h
+++ b/drivers/net/slip/slip.h
@@ -50,8 +50,6 @@


struct slip {
- int magic;
-
/* Various fields. */
struct tty_struct *tty; /* ptr to TTY structure */
struct net_device *dev; /* easy for intr handling */
@@ -100,6 +98,4 @@ struct slip {
#endif
};

-#define SLIP_MAGIC 0x5302
-
#endif /* _LINUX_SLIP.H */
--
2.30.2

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