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

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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>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Dmitry Torokhov 2016-07-25 11:36:54 -07:00
parent 887ec0bfbd
commit 4097461897
4 changed files with 24 additions and 32 deletions
Download patch file Download diff file Expand all files Collapse all files

24
include/linux/serio.h
View file

@ -31,7 +31,8 @@ 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 *);
@ -40,16 +41,29 @@ 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)