[PATCH 20/21] vgaarbiter: rst-ifiy and polish kerneldoc
Sean Paul
seanpaul at chromium.org
Mon Aug 15 20:15:17 UTC 2016
On Fri, Aug 12, 2016 at 4:48 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> 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.
>
> v4: Fix some typos (Sean).
>
> Cc: Jonathan Corbet <corbet at lwn.net>
> Cc: linux-doc at vger.kernel.org
> Cc: Sean Paul <seanpaul at chromium.org>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Reviewed-by: Sean Paul <seanpaul at chromium.org>
> ---
> 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 | 110 +++++++++++++++++++-
> include/linux/vgaarb.h | 128 +++--------------------
> 6 files changed, 316 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..1887f199ccb7 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 +373,40 @@ 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 accesses 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 differentiate 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().
> + *
> + * Returns:
> + *
> + * 0 on success, negative error code on failure.
> + */
> int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
> {
> struct vga_device *vgadev, *conflict;
> @@ -408,6 +459,21 @@ 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().
> + *
> + * Returns:
> + *
> + * 0 on success, negative error code on failure.
> + */
> int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
> {
> struct vga_device *vgadev;
> @@ -435,6 +501,16 @@ 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 +792,37 @@ 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. The
> + * driver will get a callback when VGA arbitration is first used by userspace
> + * since 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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