[PATCH] vgaarbiter: rst-ifiy and polish kerneldoc
Daniel Vetter
daniel.vetter at ffwll.ch
Tue Aug 9 13:50:28 UTC 2016
Move the documentation into Documentation/gpu, link it up and pull in
the kernel doc.
No actual text changes except that I did polish the kerneldoc a bit,
especially for vga_client_register().
v2: Remove some rst from vga-switcheroo.rst that I don't understand,
but which seems to be the reason why the new vgaarbiter.rst sometimes
drops out of the sidebar index.
v3: Drop one level of headings and clarify the vgaarb one a bit.
Cc: Jonathan Corbet <corbet at lwn.net>
Cc: linux-doc at vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
Documentation/gpu/index.rst | 1 +
Documentation/gpu/vga-switcheroo.rst | 2 -
Documentation/gpu/vgaarbiter.rst | 191 ++++++++++++++++++++++++++++++++++
Documentation/vgaarbiter.txt | 192 -----------------------------------
drivers/gpu/vga/vgaarb.c | 103 ++++++++++++++++++-
include/linux/vgaarb.h | 128 +++--------------------
6 files changed, 309 insertions(+), 308 deletions(-)
create mode 100644 Documentation/gpu/vgaarbiter.rst
delete mode 100644 Documentation/vgaarbiter.txt
diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst
index fcac0fa72056..ba92f45abb76 100644
--- a/Documentation/gpu/index.rst
+++ b/Documentation/gpu/index.rst
@@ -12,3 +12,4 @@ Linux GPU Driver Developer's Guide
drm-uapi
i915
vga-switcheroo
+ vgaarbiter
diff --git a/Documentation/gpu/vga-switcheroo.rst b/Documentation/gpu/vga-switcheroo.rst
index cbbdb994f1dd..463a74fc40d1 100644
--- a/Documentation/gpu/vga-switcheroo.rst
+++ b/Documentation/gpu/vga-switcheroo.rst
@@ -1,5 +1,3 @@
-.. _vga_switcheroo:
-
==============
VGA Switcheroo
==============
diff --git a/Documentation/gpu/vgaarbiter.rst b/Documentation/gpu/vgaarbiter.rst
new file mode 100644
index 000000000000..0b41b051d021
--- /dev/null
+++ b/Documentation/gpu/vgaarbiter.rst
@@ -0,0 +1,191 @@
+===========
+VGA Arbiter
+===========
+
+Graphic devices are accessed through ranges in I/O or memory space. While most
+modern devices allow relocation of such ranges, some "Legacy" VGA devices
+implemented on PCI will typically have the same "hard-decoded" addresses as
+they did on ISA. For more details see "PCI Bus Binding to IEEE Std 1275-1994
+Standard for Boot (Initialization Configuration) Firmware Revision 2.1"
+Section 7, Legacy Devices.
+
+The Resource Access Control (RAC) module inside the X server [0] existed for
+the legacy VGA arbitration task (besides other bus management tasks) when more
+than one legacy device co-exists on the same machine. But the problem happens
+when these devices are trying to be accessed by different userspace clients
+(e.g. two server in parallel). Their address assignments conflict. Moreover,
+ideally, being a userspace application, it is not the role of the X server to
+control bus resources. Therefore an arbitration scheme outside of the X server
+is needed to control the sharing of these resources. This document introduces
+the operation of the VGA arbiter implemented for the Linux kernel.
+
+vgaarb kernel/userspace ABI
+---------------------------
+
+The vgaarb is a module of the Linux Kernel. When it is initially loaded, it
+scans all PCI devices and adds the VGA ones inside the arbitration. The
+arbiter then enables/disables the decoding on different devices of the VGA
+legacy instructions. Devices which do not want/need to use the arbiter may
+explicitly tell it by calling vga_set_legacy_decoding().
+
+The kernel exports a char device interface (/dev/vga_arbiter) to the clients,
+which has the following semantics:
+
+open
+ Opens a user instance of the arbiter. By default, it's attached to the
+ default VGA device of the system.
+
+close
+ Close a user instance. Release locks made by the user
+
+read
+ Return a string indicating the status of the target like:
+
+ "<card_ID>,decodes=<io_state>,owns=<io_state>,locks=<io_state> (ic,mc)"
+
+ An IO state string is of the form {io,mem,io+mem,none}, mc and
+ ic are respectively mem and io lock counts (for debugging/
+ diagnostic only). "decodes" indicate what the card currently
+ decodes, "owns" indicates what is currently enabled on it, and
+ "locks" indicates what is locked by this card. If the card is
+ unplugged, we get "invalid" then for card_ID and an -ENODEV
+ error is returned for any command until a new card is targeted.
+
+
+write
+ Write a command to the arbiter. List of commands:
+
+ target <card_ID>
+ switch target to card <card_ID> (see below)
+ lock <io_state>
+ acquires locks on target ("none" is an invalid io_state)
+ trylock <io_state>
+ non-blocking acquire locks on target (returns EBUSY if
+ unsuccessful)
+ unlock <io_state>
+ release locks on target
+ unlock all
+ release all locks on target held by this user (not implemented
+ yet)
+ decodes <io_state>
+ set the legacy decoding attributes for the card
+
+ poll
+ event if something changes on any card (not just the target)
+
+ card_ID is of the form "PCI:domain:bus:dev.fn". It can be set to "default"
+ to go back to the system default card (TODO: not implemented yet). Currently,
+ only PCI is supported as a prefix, but the userland API may support other bus
+ types in the future, even if the current kernel implementation doesn't.
+
+Note about locks:
+
+The driver keeps track of which user has which locks on which card. It
+supports stacking, like the kernel one. This complexifies the implementation
+a bit, but makes the arbiter more tolerant to user space problems and able
+to properly cleanup in all cases when a process dies.
+Currently, a max of 16 cards can have locks simultaneously issued from
+user space for a given user (file descriptor instance) of the arbiter.
+
+In the case of devices hot-{un,}plugged, there is a hook - pci_notify() - to
+notify them being added/removed in the system and automatically added/removed
+in the arbiter.
+
+There is also an in-kernel API of the arbiter in case DRM, vgacon, or other
+drivers want to use it.
+
+In-kernel interface
+-------------------
+
+.. kernel-doc:: include/linux/vgaarb.h
+ :internal:
+
+.. kernel-doc:: drivers/gpu/vga/vgaarb.c
+ :export:
+
+libpciaccess
+------------
+
+To use the vga arbiter char device it was implemented an API inside the
+libpciaccess library. One field was added to struct pci_device (each device
+on the system)::
+
+ /* the type of resource decoded by the device */
+ int vgaarb_rsrc;
+
+Besides it, in pci_system were added::
+
+ int vgaarb_fd;
+ int vga_count;
+ struct pci_device *vga_target;
+ struct pci_device *vga_default_dev;
+
+The vga_count is used to track how many cards are being arbitrated, so for
+instance, if there is only one card, then it can completely escape arbitration.
+
+These functions below acquire VGA resources for the given card and mark those
+resources as locked. If the resources requested are "normal" (and not legacy)
+resources, the arbiter will first check whether the card is doing legacy
+decoding for that type of resource. If yes, the lock is "converted" into a
+legacy resource lock. The arbiter will first look for all VGA cards that
+might conflict and disable their IOs and/or Memory access, including VGA
+forwarding on P2P bridges if necessary, so that the requested resources can
+be used. Then, the card is marked as locking these resources and the IO and/or
+Memory access is enabled on the card (including VGA forwarding on parent
+P2P bridges if any). In the case of vga_arb_lock(), the function will block
+if some conflicting card is already locking one of the required resources (or
+any resource on a different bus segment, since P2P bridges don't differentiate
+VGA memory and IO afaik). If the card already owns the resources, the function
+succeeds. vga_arb_trylock() will return (-EBUSY) instead of blocking. Nested
+calls are supported (a per-resource counter is maintained).
+
+Set the target device of this client. ::
+
+ int pci_device_vgaarb_set_target (struct pci_device *dev);
+
+For instance, in x86 if two devices on the same bus want to lock different
+resources, both will succeed (lock). If devices are in different buses and
+trying to lock different resources, only the first who tried succeeds. ::
+
+ int pci_device_vgaarb_lock (void);
+ int pci_device_vgaarb_trylock (void);
+
+Unlock resources of device. ::
+
+ int pci_device_vgaarb_unlock (void);
+
+Indicates to the arbiter if the card decodes legacy VGA IOs, legacy VGA
+Memory, both, or none. All cards default to both, the card driver (fbdev for
+example) should tell the arbiter if it has disabled legacy decoding, so the
+card can be left out of the arbitration process (and can be safe to take
+interrupts at any time. ::
+
+ int pci_device_vgaarb_decodes (int new_vgaarb_rsrc);
+
+Connects to the arbiter device, allocates the struct ::
+
+ int pci_device_vgaarb_init (void);
+
+Close the connection ::
+
+ void pci_device_vgaarb_fini (void);
+
+xf86VGAArbiter (X server implementation)
+----------------------------------------
+
+X server basically wraps all the functions that touch VGA registers somehow.
+
+References
+----------
+
+Benjamin Herrenschmidt (IBM?) started this work when he discussed such design
+with the Xorg community in 2005 [1, 2]. In the end of 2007, Paulo Zanoni and
+Tiago Vignatti (both of C3SL/Federal University of Paraná) proceeded his work
+enhancing the kernel code to adapt as a kernel module and also did the
+implementation of the user space side [3]. Now (2009) Tiago Vignatti and Dave
+Airlie finally put this work in shape and queued to Jesse Barnes' PCI tree.
+
+0) http://cgit.freedesktop.org/xorg/xserver/commit/?id=4b42448a2388d40f257774fbffdccaea87bd0347
+1) http://lists.freedesktop.org/archives/xorg/2005-March/006663.html
+2) http://lists.freedesktop.org/archives/xorg/2005-March/006745.html
+3) http://lists.freedesktop.org/archives/xorg/2007-October/029507.html
diff --git a/Documentation/vgaarbiter.txt b/Documentation/vgaarbiter.txt
deleted file mode 100644
index 014423e2824c..000000000000
--- a/Documentation/vgaarbiter.txt
+++ /dev/null
@@ -1,192 +0,0 @@
-
-VGA Arbiter
-===========
-
-Graphic devices are accessed through ranges in I/O or memory space. While most
-modern devices allow relocation of such ranges, some "Legacy" VGA devices
-implemented on PCI will typically have the same "hard-decoded" addresses as
-they did on ISA. For more details see "PCI Bus Binding to IEEE Std 1275-1994
-Standard for Boot (Initialization Configuration) Firmware Revision 2.1"
-Section 7, Legacy Devices.
-
-The Resource Access Control (RAC) module inside the X server [0] existed for
-the legacy VGA arbitration task (besides other bus management tasks) when more
-than one legacy device co-exists on the same machine. But the problem happens
-when these devices are trying to be accessed by different userspace clients
-(e.g. two server in parallel). Their address assignments conflict. Moreover,
-ideally, being a userspace application, it is not the role of the X server to
-control bus resources. Therefore an arbitration scheme outside of the X server
-is needed to control the sharing of these resources. This document introduces
-the operation of the VGA arbiter implemented for the Linux kernel.
-
-----------------------------------------------------------------------------
-
-I. Details and Theory of Operation
- I.1 vgaarb
- I.2 libpciaccess
- I.3 xf86VGAArbiter (X server implementation)
-II. Credits
-III.References
-
-
-I. Details and Theory of Operation
-==================================
-
-I.1 vgaarb
-----------
-
-The vgaarb is a module of the Linux Kernel. When it is initially loaded, it
-scans all PCI devices and adds the VGA ones inside the arbitration. The
-arbiter then enables/disables the decoding on different devices of the VGA
-legacy instructions. Devices which do not want/need to use the arbiter may
-explicitly tell it by calling vga_set_legacy_decoding().
-
-The kernel exports a char device interface (/dev/vga_arbiter) to the clients,
-which has the following semantics:
-
- open : open user instance of the arbiter. By default, it's attached to
- the default VGA device of the system.
-
- close : close user instance. Release locks made by the user
-
- read : return a string indicating the status of the target like:
-
- "<card_ID>,decodes=<io_state>,owns=<io_state>,locks=<io_state> (ic,mc)"
-
- An IO state string is of the form {io,mem,io+mem,none}, mc and
- ic are respectively mem and io lock counts (for debugging/
- diagnostic only). "decodes" indicate what the card currently
- decodes, "owns" indicates what is currently enabled on it, and
- "locks" indicates what is locked by this card. If the card is
- unplugged, we get "invalid" then for card_ID and an -ENODEV
- error is returned for any command until a new card is targeted.
-
-
- write : write a command to the arbiter. List of commands:
-
- target <card_ID> : switch target to card <card_ID> (see below)
- lock <io_state> : acquires locks on target ("none" is an invalid io_state)
- trylock <io_state> : non-blocking acquire locks on target (returns EBUSY if
- unsuccessful)
- unlock <io_state> : release locks on target
- unlock all : release all locks on target held by this user (not
- implemented yet)
- decodes <io_state> : set the legacy decoding attributes for the card
-
- poll : event if something changes on any card (not just the
- target)
-
- card_ID is of the form "PCI:domain:bus:dev.fn". It can be set to "default"
- to go back to the system default card (TODO: not implemented yet). Currently,
- only PCI is supported as a prefix, but the userland API may support other bus
- types in the future, even if the current kernel implementation doesn't.
-
-Note about locks:
-
-The driver keeps track of which user has which locks on which card. It
-supports stacking, like the kernel one. This complexifies the implementation
-a bit, but makes the arbiter more tolerant to user space problems and able
-to properly cleanup in all cases when a process dies.
-Currently, a max of 16 cards can have locks simultaneously issued from
-user space for a given user (file descriptor instance) of the arbiter.
-
-In the case of devices hot-{un,}plugged, there is a hook - pci_notify() - to
-notify them being added/removed in the system and automatically added/removed
-in the arbiter.
-
-There is also an in-kernel API of the arbiter in case DRM, vgacon, or other
-drivers want to use it.
-
-
-I.2 libpciaccess
-----------------
-
-To use the vga arbiter char device it was implemented an API inside the
-libpciaccess library. One field was added to struct pci_device (each device
-on the system):
-
- /* the type of resource decoded by the device */
- int vgaarb_rsrc;
-
-Besides it, in pci_system were added:
-
- int vgaarb_fd;
- int vga_count;
- struct pci_device *vga_target;
- struct pci_device *vga_default_dev;
-
-
-The vga_count is used to track how many cards are being arbitrated, so for
-instance, if there is only one card, then it can completely escape arbitration.
-
-
-These functions below acquire VGA resources for the given card and mark those
-resources as locked. If the resources requested are "normal" (and not legacy)
-resources, the arbiter will first check whether the card is doing legacy
-decoding for that type of resource. If yes, the lock is "converted" into a
-legacy resource lock. The arbiter will first look for all VGA cards that
-might conflict and disable their IOs and/or Memory access, including VGA
-forwarding on P2P bridges if necessary, so that the requested resources can
-be used. Then, the card is marked as locking these resources and the IO and/or
-Memory access is enabled on the card (including VGA forwarding on parent
-P2P bridges if any). In the case of vga_arb_lock(), the function will block
-if some conflicting card is already locking one of the required resources (or
-any resource on a different bus segment, since P2P bridges don't differentiate
-VGA memory and IO afaik). If the card already owns the resources, the function
-succeeds. vga_arb_trylock() will return (-EBUSY) instead of blocking. Nested
-calls are supported (a per-resource counter is maintained).
-
-
-Set the target device of this client.
- int pci_device_vgaarb_set_target (struct pci_device *dev);
-
-
-For instance, in x86 if two devices on the same bus want to lock different
-resources, both will succeed (lock). If devices are in different buses and
-trying to lock different resources, only the first who tried succeeds.
- int pci_device_vgaarb_lock (void);
- int pci_device_vgaarb_trylock (void);
-
-Unlock resources of device.
- int pci_device_vgaarb_unlock (void);
-
-Indicates to the arbiter if the card decodes legacy VGA IOs, legacy VGA
-Memory, both, or none. All cards default to both, the card driver (fbdev for
-example) should tell the arbiter if it has disabled legacy decoding, so the
-card can be left out of the arbitration process (and can be safe to take
-interrupts at any time.
- int pci_device_vgaarb_decodes (int new_vgaarb_rsrc);
-
-Connects to the arbiter device, allocates the struct
- int pci_device_vgaarb_init (void);
-
-Close the connection
- void pci_device_vgaarb_fini (void);
-
-
-I.3 xf86VGAArbiter (X server implementation)
---------------------------------------------
-
-(TODO)
-
-X server basically wraps all the functions that touch VGA registers somehow.
-
-
-II. Credits
-===========
-
-Benjamin Herrenschmidt (IBM?) started this work when he discussed such design
-with the Xorg community in 2005 [1, 2]. In the end of 2007, Paulo Zanoni and
-Tiago Vignatti (both of C3SL/Federal University of Paraná) proceeded his work
-enhancing the kernel code to adapt as a kernel module and also did the
-implementation of the user space side [3]. Now (2009) Tiago Vignatti and Dave
-Airlie finally put this work in shape and queued to Jesse Barnes' PCI tree.
-
-
-III. References
-==============
-
-[0] http://cgit.freedesktop.org/xorg/xserver/commit/?id=4b42448a2388d40f257774fbffdccaea87bd0347
-[1] http://lists.freedesktop.org/archives/xorg/2005-March/006663.html
-[2] http://lists.freedesktop.org/archives/xorg/2005-March/006745.html
-[3] http://lists.freedesktop.org/archives/xorg/2007-October/029507.html
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index f17cb0431833..92787f20b7f7 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -131,7 +131,24 @@ static struct vga_device *vgadev_find(struct pci_dev *pdev)
return NULL;
}
-/* Returns the default VGA device (vgacon's babe) */
+/**
+ * vga_default_device - return the default VGA device, for vgacon
+ *
+ * This can be defined by the platform. The default implementation
+ * is rather dumb and will probably only work properly on single
+ * vga card setups and/or x86 platforms.
+ *
+ * If your VGA default device is not PCI, you'll have to return
+ * NULL here. In this case, I assume it will not conflict with
+ * any PCI card. If this is not true, I'll have to define two archs
+ * hooks for enabling/disabling the VGA default device if that is
+ * possible. This may be a problem with real _ISA_ VGA cards, in
+ * addition to a PCI one. I don't know at this point how to deal
+ * with that card. Can theirs IOs be disabled at all ? If not, then
+ * I suppose it's a matter of having the proper arch hook telling
+ * us about it, so we basically never allow anybody to succeed a
+ * vga_get()...
+ */
struct pci_dev *vga_default_device(void)
{
return vga_default;
@@ -356,6 +373,36 @@ static void __vga_put(struct vga_device *vgadev, unsigned int rsrc)
wake_up_all(&vga_wait_queue);
}
+/**
+ * vga_get - acquire & locks VGA resources
+ * @pdev: pci device of the VGA card or NULL for the system default
+ * @rsrc: bit mask of resources to acquire and lock
+ * @interruptible: blocking should be interruptible by signals ?
+ *
+ * This function acquires VGA resources for the given card and mark those
+ * resources locked. If the resource requested are "normal" (and not legacy)
+ * resources, the arbiter will first check whether the card is doing legacy
+ * decoding for that type of resource. If yes, the lock is "converted" into a
+ * legacy resource lock.
+ *
+ * The arbiter will first look for all VGA cards that might conflict and disable
+ * their IOs and/or Memory access, including VGA forwarding on P2P bridges if
+ * necessary, so that the requested resources can be used. Then, the card is
+ * marked as locking these resources and the IO and/or Memory accesse are
+ * enabled on the card (including VGA forwarding on parent P2P bridges if any).
+ *
+ * This function will block if some conflicting card is already locking one of
+ * the required resources (or any resource on a different bus segment, since P2P
+ * bridges don't differenciate VGA memory and IO afaik). You can indicate
+ * whether this blocking should be interruptible by a signal (for userland
+ * interface) or not.
+ *
+ * Must not be called at interrupt time or in atomic context. If the card
+ * already owns the resources, the function succeeds. Nested calls are
+ * supported (a per-resource counter is maintained)
+ *
+ * On success, release the VGA resource again with vga_put().
+ */
int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
{
struct vga_device *vgadev, *conflict;
@@ -408,6 +455,17 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
}
EXPORT_SYMBOL(vga_get);
+/**
+ * vga_tryget - try to acquire & lock legacy VGA resources
+ * @pdev: pci devivce of VGA card or NULL for system default
+ * @rsrc: bit mask of resources to acquire and lock
+ *
+ * This function performs the same operation as vga_get(), but will return an
+ * error (-EBUSY) instead of blocking if the resources are already locked by
+ * another card. It can be called in any context
+ *
+ * On success, release the VGA resource again with vga_put().
+ */
int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
{
struct vga_device *vgadev;
@@ -435,6 +493,16 @@ bail:
}
EXPORT_SYMBOL(vga_tryget);
+/**
+ * vga_put - release lock on legacy VGA resources
+ * @pdev: pci device of VGA card or NULL for system default
+ * @rsrc: but mask of resource to release
+ *
+ * This fuction releases resources previously locked by vga_get() or
+ * vga_tryget(). The resources aren't disabled right away, so that a subsequence
+ * vga_get() on the same card will succeed immediately. Resources have a
+ * counter, so locks are only released if the counter reaches 0.
+ */
void vga_put(struct pci_dev *pdev, unsigned int rsrc)
{
struct vga_device *vgadev;
@@ -716,7 +784,38 @@ void vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes)
}
EXPORT_SYMBOL(vga_set_legacy_decoding);
-/* call with NULL to unregister */
+/**
+ * vga_client_register - register or unregister a VGA arbitration client
+ * @pdev: pci device of the VGA client
+ * @cookie: client cookie to be used in callbacks
+ * @irq_set_state: irq state change callback
+ * @set_vga_decode: vga decode change callback
+ *
+ * Clients have two callback mechanisms they can use.
+ *
+ * @irq_set_state callback: If a client can't disable its GPUs VGA
+ * resources, then we need to be able to ask it to turn off its irqs when we
+ * turn off its mem and io decoding.
+ *
+ * @set_vga_decode callback: If a client can disable its GPU VGA resource, it
+ * will get a callback from this to set the encode/decode state.
+ *
+ * Rationale: we cannot disable VGA decode resources unconditionally
+ * some single GPU laptops seem to require ACPI or BIOS access to the
+ * VGA registers to control things like backlights etc.
+ * Hopefully newer multi-GPU laptops do something saner, and desktops
+ * won't have any special ACPI for this.
+ * They driver will get a callback when VGA arbitration is first used
+ * by userspace since we some older X servers have issues.
+ *
+ * This function does not check whether a client for @pdev has been registered
+ * already.
+ *
+ * To unregister just call this function with @irq_set_state and @set_vga_decode
+ * both set to NULL for the same @pdev as originally used to register them.
+ *
+ * Returns: 0 on success, -1 on failure
+ */
int vga_client_register(struct pci_dev *pdev, void *cookie,
void (*irq_set_state)(void *cookie, bool state),
unsigned int (*set_vga_decode)(void *cookie,
diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
index 8c3b412d84df..ee162e3e879b 100644
--- a/include/linux/vgaarb.h
+++ b/include/linux/vgaarb.h
@@ -73,34 +73,6 @@ static inline void vga_set_legacy_decoding(struct pci_dev *pdev,
unsigned int decodes) { };
#endif
-/**
- * vga_get - acquire & locks VGA resources
- *
- * @pdev: pci device of the VGA card or NULL for the system default
- * @rsrc: bit mask of resources to acquire and lock
- * @interruptible: blocking should be interruptible by signals ?
- *
- * This function acquires VGA resources for the given
- * card and mark those resources locked. If the resource requested
- * are "normal" (and not legacy) resources, the arbiter will first check
- * whether the card is doing legacy decoding for that type of resource. If
- * yes, the lock is "converted" into a legacy resource lock.
- * The arbiter will first look for all VGA cards that might conflict
- * and disable their IOs and/or Memory access, including VGA forwarding
- * on P2P bridges if necessary, so that the requested resources can
- * be used. Then, the card is marked as locking these resources and
- * the IO and/or Memory accesse are enabled on the card (including
- * VGA forwarding on parent P2P bridges if any).
- * This function will block if some conflicting card is already locking
- * one of the required resources (or any resource on a different bus
- * segment, since P2P bridges don't differenciate VGA memory and IO
- * afaik). You can indicate whether this blocking should be interruptible
- * by a signal (for userland interface) or not.
- * Must not be called at interrupt time or in atomic context.
- * If the card already owns the resources, the function succeeds.
- * Nested calls are supported (a per-resource counter is maintained)
- */
-
#if defined(CONFIG_VGA_ARB)
extern int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible);
#else
@@ -108,11 +80,14 @@ static inline int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interrupt
#endif
/**
- * vga_get_interruptible
+ * vga_get_interruptible
+ * @pdev: pci device of the VGA card or NULL for the system default
+ * @rsrc: bit mask of resources to acquire and lock
*
- * Shortcut to vga_get
+ * Shortcut to vga_get with interruptible set to true.
+ *
+ * On success, release the VGA resource again with vga_put().
*/
-
static inline int vga_get_interruptible(struct pci_dev *pdev,
unsigned int rsrc)
{
@@ -120,47 +95,26 @@ static inline int vga_get_interruptible(struct pci_dev *pdev,
}
/**
- * vga_get_uninterruptible
+ * vga_get_uninterruptible - shortcut to vga_get()
+ * @pdev: pci device of the VGA card or NULL for the system default
+ * @rsrc: bit mask of resources to acquire and lock
*
- * Shortcut to vga_get
+ * Shortcut to vga_get with interruptible set to false.
+ *
+ * On success, release the VGA resource again with vga_put().
*/
-
static inline int vga_get_uninterruptible(struct pci_dev *pdev,
unsigned int rsrc)
{
return vga_get(pdev, rsrc, 0);
}
-/**
- * vga_tryget - try to acquire & lock legacy VGA resources
- *
- * @pdev: pci devivce of VGA card or NULL for system default
- * @rsrc: bit mask of resources to acquire and lock
- *
- * This function performs the same operation as vga_get(), but
- * will return an error (-EBUSY) instead of blocking if the resources
- * are already locked by another card. It can be called in any context
- */
-
#if defined(CONFIG_VGA_ARB)
extern int vga_tryget(struct pci_dev *pdev, unsigned int rsrc);
#else
static inline int vga_tryget(struct pci_dev *pdev, unsigned int rsrc) { return 0; }
#endif
-/**
- * vga_put - release lock on legacy VGA resources
- *
- * @pdev: pci device of VGA card or NULL for system default
- * @rsrc: but mask of resource to release
- *
- * This function releases resources previously locked by vga_get()
- * or vga_tryget(). The resources aren't disabled right away, so
- * that a subsequence vga_get() on the same card will succeed
- * immediately. Resources have a counter, so locks are only
- * released if the counter reaches 0.
- */
-
#if defined(CONFIG_VGA_ARB)
extern void vga_put(struct pci_dev *pdev, unsigned int rsrc);
#else
@@ -168,25 +122,6 @@ extern void vga_put(struct pci_dev *pdev, unsigned int rsrc);
#endif
-/**
- * vga_default_device
- *
- * This can be defined by the platform. The default implementation
- * is rather dumb and will probably only work properly on single
- * vga card setups and/or x86 platforms.
- *
- * If your VGA default device is not PCI, you'll have to return
- * NULL here. In this case, I assume it will not conflict with
- * any PCI card. If this is not true, I'll have to define two archs
- * hooks for enabling/disabling the VGA default device if that is
- * possible. This may be a problem with real _ISA_ VGA cards, in
- * addition to a PCI one. I don't know at this point how to deal
- * with that card. Can theirs IOs be disabled at all ? If not, then
- * I suppose it's a matter of having the proper arch hook telling
- * us about it, so we basically never allow anybody to succeed a
- * vga_get()...
- */
-
#ifdef CONFIG_VGA_ARB
extern struct pci_dev *vga_default_device(void);
extern void vga_set_default_device(struct pci_dev *pdev);
@@ -195,14 +130,11 @@ static inline struct pci_dev *vga_default_device(void) { return NULL; };
static inline void vga_set_default_device(struct pci_dev *pdev) { };
#endif
-/**
- * vga_conflicts
- *
- * Architectures should define this if they have several
- * independent PCI domains that can afford concurrent VGA
- * decoding
+/*
+ * Architectures should define this if they have several
+ * independent PCI domains that can afford concurrent VGA
+ * decoding
*/
-
#ifndef __ARCH_HAS_VGA_CONFLICT
static inline int vga_conflicts(struct pci_dev *p1, struct pci_dev *p2)
{
@@ -210,34 +142,6 @@ static inline int vga_conflicts(struct pci_dev *p1, struct pci_dev *p2)
}
#endif
-/**
- * vga_client_register
- *
- * @pdev: pci device of the VGA client
- * @cookie: client cookie to be used in callbacks
- * @irq_set_state: irq state change callback
- * @set_vga_decode: vga decode change callback
- *
- * return value: 0 on success, -1 on failure
- * Register a client with the VGA arbitration logic
- *
- * Clients have two callback mechanisms they can use.
- * irq enable/disable callback -
- * If a client can't disable its GPUs VGA resources, then we
- * need to be able to ask it to turn off its irqs when we
- * turn off its mem and io decoding.
- * set_vga_decode
- * If a client can disable its GPU VGA resource, it will
- * get a callback from this to set the encode/decode state
- *
- * Rationale: we cannot disable VGA decode resources unconditionally
- * some single GPU laptops seem to require ACPI or BIOS access to the
- * VGA registers to control things like backlights etc.
- * Hopefully newer multi-GPU laptops do something saner, and desktops
- * won't have any special ACPI for this.
- * They driver will get a callback when VGA arbitration is first used
- * by userspace since we some older X servers have issues.
- */
#if defined(CONFIG_VGA_ARB)
int vga_client_register(struct pci_dev *pdev, void *cookie,
void (*irq_set_state)(void *cookie, bool state),
--
2.8.1
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