/*
 * V4L2 asynchronous subdevice registration API
 *
 * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#ifndef V4L2_ASYNC_H
#define V4L2_ASYNC_H

#include <linux/list.h>
#include <linux/mutex.h>

struct device;
struct device_node;
struct v4l2_device;
struct v4l2_subdev;
struct v4l2_async_notifier;

/* A random max subdevice number, used to allocate an array on stack */
#define V4L2_MAX_SUBDEVS 128U

/**
 * enum v4l2_async_match_type - type of asynchronous subdevice logic to be used
 *	in order to identify a match
 *
 * @V4L2_ASYNC_MATCH_CUSTOM: Match will use the logic provided by &struct
 * 	v4l2_async_subdev.match ops
 * @V4L2_ASYNC_MATCH_DEVNAME: Match will use the device name
 * @V4L2_ASYNC_MATCH_I2C: Match will check for I2C adapter ID and address
 * @V4L2_ASYNC_MATCH_OF: Match will use OF node
 *
 * This enum is used by the asyncrhronous sub-device logic to define the
 * algorithm that will be used to match an asynchronous device.
 */
enum v4l2_async_match_type {
	V4L2_ASYNC_MATCH_CUSTOM,
	V4L2_ASYNC_MATCH_DEVNAME,
	V4L2_ASYNC_MATCH_I2C,
	V4L2_ASYNC_MATCH_OF,
};

/**
 * struct v4l2_async_subdev - sub-device descriptor, as known to a bridge
 *
 * @match_type:	type of match that will be used
 * @match:	union of per-bus type matching data sets
 * @list:	used to link struct v4l2_async_subdev objects, waiting to be
 *		probed, to a notifier->waiting list
 */
struct v4l2_async_subdev {
	enum v4l2_async_match_type match_type;
	union {
		struct {
			const struct device_node *node;
		} of;
		struct {
			const char *name;
		} device_name;
		struct {
			int adapter_id;
			unsigned short address;
		} i2c;
		struct {
			bool (*match)(struct device *,
				      struct v4l2_async_subdev *);
			void *priv;
		} custom;
	} match;

	/* v4l2-async core private: not to be used by drivers */
	struct list_head list;
};

/**
 * struct v4l2_async_notifier - v4l2_device notifier data
 *
 * @num_subdevs: number of subdevices
 * @subdevs:	array of pointers to subdevice descriptors
 * @v4l2_dev:	pointer to struct v4l2_device
 * @waiting:	list of struct v4l2_async_subdev, waiting for their drivers
 * @done:	list of struct v4l2_subdev, already probed
 * @list:	member in a global list of notifiers
 * @bound:	a subdevice driver has successfully probed one of subdevices
 * @complete:	all subdevices have been probed successfully
 * @unbind:	a subdevice is leaving
 */
struct v4l2_async_notifier {
	unsigned int num_subdevs;
	struct v4l2_async_subdev **subdevs;
	struct v4l2_device *v4l2_dev;
	struct list_head waiting;
	struct list_head done;
	struct list_head list;
	int (*bound)(struct v4l2_async_notifier *notifier,
		     struct v4l2_subdev *subdev,
		     struct v4l2_async_subdev *asd);
	int (*complete)(struct v4l2_async_notifier *notifier);
	void (*unbind)(struct v4l2_async_notifier *notifier,
		       struct v4l2_subdev *subdev,
		       struct v4l2_async_subdev *asd);
};

/**
 * v4l2_async_notifier_register - registers a subdevice asynchronous notifier
 *
 * @v4l2_dev: pointer to &struct v4l2_device
 * @notifier: pointer to &struct v4l2_async_notifier
 */
int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
				 struct v4l2_async_notifier *notifier);

/**
 * v4l2_async_notifier_unregister - unregisters a subdevice asynchronous notifier
 *
 * @notifier: pointer to &struct v4l2_async_notifier
 */
void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier);

/**
 * v4l2_async_register_subdev - registers a sub-device to the asynchronous
 * 	subdevice framework
 *
 * @sd: pointer to &struct v4l2_subdev
 */
int v4l2_async_register_subdev(struct v4l2_subdev *sd);

/**
 * v4l2_async_unregister_subdev - unregisters a sub-device to the asynchronous
 * 	subdevice framework
 *
 * @sd: pointer to &struct v4l2_subdev
 */
void v4l2_async_unregister_subdev(struct v4l2_subdev *sd);
#endif
e='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/gadget/usbstring.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/drivers/usb/gadget/usbstring.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/drivers/usb/gadget/usbstring.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>drivers/usb/gadget/usbstring.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/gadget/usbstring.c?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/drivers/usb/gadget/usbstring.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'drivers/usb/gadget/usbstring.c')</div><table summary='diffstat' class='diffstat'>