Input: i8042 - break load dependency between atkbd/psmouse and i8042

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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
index 178e75d..514553b 100644 (file)
--- 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 __devexit 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 (file)
--- 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 (file)
--- 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 ca82861..34b403a 100644 (file)
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -33,7 +33,8 @@ 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 *);
@@ -42,16 +43,29 @@ 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)