[PATCH 3.10 183/319] Input: i8042 - break load dependency between atkbd/psmouse and i8042

Willy Tarreau
2017-02-05T20:00:39Z

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>

commit 4097461897df91041382ff6fcd2bfa7ee6b2448c upstream.

As explained in 1407814240-4275-1-git-send-email-decui@microsoft.com we
have a hard load dependency between i8042 and atkbd which prevents
keyboard from working on Gen2 Hyper-V VMs.

> hyperv_keyboard invokes serio_interrupt(), which needs a valid serio
> driver like atkbd.c. atkbd.c depends on libps2.c because it invokes
> ps2_command(). libps2.c depends on i8042.c because it invokes
> i8042_check_port_owner(). As a result, hyperv_keyboard actually
> depends on i8042.c.
>
> For a Generation 2 Hyper-V VM (meaning no i8042 device emulated), if a
> Linux VM (like Arch Linux) happens to configure CONFIG_SERIO_I8042=m
> rather than =y, atkbd.ko can't load because i8042.ko can't load(due to
> no i8042 device emulated) and finally hyperv_keyboard can't work and
> the user can't input: https://bugs.archlinux.org/task/39820
> (Ubuntu/RHEL/SUSE aren't affected since they use CONFIG_SERIO_I8042=y)

To break the dependency we move away from using i8042_check_port_owner()
and instead allow serio port owner specify a mutex that clients should use
to serialize PS/2 command stream.

Reported-by: Mark Laws <mdl@60hz.org>
Tested-by: Mark Laws <mdl@60hz.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
drivers/input/serio/i8042.c | 16 +---------------
drivers/input/serio/libps2.c | 10 ++++------
include/linux/i8042.h | 6 ------
include/linux/serio.h | 24 +++++++++++++++++++-----
4 files changed, 24 insertions(+), 32 deletions(-)

diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
index 9870c54..2513c8a 100644
--- a/drivers/input/serio/i8042.c
+++ b/drivers/input/serio/i8042.c
@@ -1223,6 +1223,7 @@ static int __init i8042_create_kbd_port(void)
serio->start = i8042_start;
serio->stop = i8042_stop;
serio->close = i8042_port_close;
+ serio->ps2_cmd_mutex = &i8042_mutex;
serio->port_data = port;
serio->dev.parent = &i8042_platform_device->dev;
strlcpy(serio->name, "i8042 KBD port", sizeof(serio->name));
@@ -1310,21 +1311,6 @@ static void i8042_unregister_ports(void)
}
}

-/*
- * Checks whether port belongs to i8042 controller.
- */
-bool i8042_check_port_owner(const struct serio *port)
-{
- int i;
-
- for (i = 0; i < I8042_NUM_PORTS; i++)
- if (i8042_ports[i].serio == port)
- return true;
-
- return false;
-}
-EXPORT_SYMBOL(i8042_check_port_owner);
-
static void i8042_free_irqs(void)
{
if (i8042_aux_irq_registered)
diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
index 07a8363..b5ec313 100644
--- a/drivers/input/serio/libps2.c
+++ b/drivers/input/serio/libps2.c
@@ -57,19 +57,17 @@ EXPORT_SYMBOL(ps2_sendbyte);

void ps2_begin_command(struct ps2dev *ps2dev)
{
- mutex_lock(&ps2dev->cmd_mutex);
+ struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;

- if (i8042_check_port_owner(ps2dev->serio))
- i8042_lock_chip();
+ mutex_lock(m);
}
EXPORT_SYMBOL(ps2_begin_command);

void ps2_end_command(struct ps2dev *ps2dev)
{
- if (i8042_check_port_owner(ps2dev->serio))
- i8042_unlock_chip();
+ struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;

- mutex_unlock(&ps2dev->cmd_mutex);
+ mutex_unlock(m);
}
EXPORT_SYMBOL(ps2_end_command);

diff --git a/include/linux/i8042.h b/include/linux/i8042.h
index a986ff5..801c307 100644
--- a/include/linux/i8042.h
+++ b/include/linux/i8042.h
@@ -38,7 +38,6 @@ struct serio;
void i8042_lock_chip(void);
void i8042_unlock_chip(void);
int i8042_command(unsigned char *param, int command);
-bool i8042_check_port_owner(const struct serio *);
int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
struct serio *serio));
int i8042_remove_filter(bool (*filter)(unsigned char data, unsigned char str,
@@ -59,11 +58,6 @@ static inline int i8042_command(unsigned char *param, int command)
return -ENODEV;
}

-static inline bool i8042_check_port_owner(const struct serio *serio)
-{
- return false;
-}
-
static inline int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
struct serio *serio))
{
diff --git a/include/linux/serio.h b/include/linux/serio.h
index 36aac73..deffa474 100644
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -28,7 +28,8 @@ struct serio {

struct serio_device_id id;

- spinlock_t lock; /* protects critical sections from port's interrupt handler */
+ /* Protects critical sections from port's interrupt handler */
+ spinlock_t lock;

int (*write)(struct serio *, unsigned char);
int (*open)(struct serio *);
@@ -37,16 +38,29 @@ struct serio {
void (*stop)(struct serio *);

struct serio *parent;
- struct list_head child_node; /* Entry in parent->children list */
+ /* Entry in parent->children list */
+ struct list_head child_node;
struct list_head children;
- unsigned int depth; /* level of nesting in serio hierarchy */
+ /* Level of nesting in serio hierarchy */
+ unsigned int depth;

- struct serio_driver *drv; /* accessed from interrupt, must be protected by serio->lock and serio->sem */
- struct mutex drv_mutex; /* protects serio->drv so attributes can pin driver */
+ /*
+ * serio->drv is accessed from interrupt handlers; when modifying
+ * caller should acquire serio->drv_mutex and serio->lock.
+ */
+ struct serio_driver *drv;
+ /* Protects serio->drv so attributes can pin current driver */
+ struct mutex drv_mutex;

struct device dev;

struct list_head node;
+
+ /*
+ * For use by PS/2 layer when several ports share hardware and
+ * may get indigestion when exposed to concurrent access (i8042).
+ */
+ struct mutex *ps2_cmd_mutex;
};
#define to_serio_port(d) container_of(d, struct serio, dev)

--
2.8.0.rc2.1.gbe9624a