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Message-ID: <b3d7b7fc-5b3b-0109-f53d-fea3c6618728@loongson.cn>
Date:   Thu, 24 Aug 2023 14:21:22 +0800
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Subject: Re: [PATCH v2 00/11] Fix typos, comments and copyright
To:     Bjorn Helgaas <helgaas@kernel.org>,
        Sui Jingfeng <sui.jingfeng@linux.dev>
Cc:     Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Dave Airlie <airlied@redhat.com>
References: <20230823222910.GA495298@bhelgaas>
Content-Language: en-US
From:   suijingfeng <suijingfeng@loongson.cn>
In-Reply-To: <20230823222910.GA495298@bhelgaas>
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Hi,


Nice cleanup, thanks a lot.


On 2023/8/24 06:29, Bjorn Helgaas wrote:
> On Wed, Aug 09, 2023 at 06:34:01AM +0800, Sui Jingfeng wrote:
>> From: Sui Jingfeng <suijingfeng@loongson.cn>
>>
>> v1:
>> 	* Various improve.
>> v2:
>> 	* More fixes, optimizations and improvements.
>>
>> Sui Jingfeng (11):
>>    PCI/VGA: Use unsigned type for the io_state variable
>>    PCI: Add the pci_get_class_masked() helper
>>    PCI/VGA: Deal with VGA class devices
> I dropped these two patches, at least for now.  There's no other use
> of pci_get_class_masked(), and the VGA use seems to be mostly
> optimization and possibly some behavior change that isn't 100% clear
> yet.  If it's important, we can look at it again later.


OK, no problem.


>>    PCI/VGA: Drop the inline in the vga_update_device_decodes() function.
>>    PCI/VGA: Move the new_state assignment out of the loop
>>    PCI/VGA: Fix two typos in the comments of pci_notify()
>>    PCI/VGA: vga_client_register() return -ENODEV on failure, not -1
>>    PCI/VGA: Fix a typo to the comment of vga_default
>>    PCI/VGA: Fix a typo to the comments in vga_str_to_iostate() function
>>    PCI/VGA: Tidy up the code and comment format
>>    PCI/VGA: Replace full MIT license text with SPDX identifier
>>
>>   drivers/pci/search.c   |  30 ++++++
>>   drivers/pci/vgaarb.c   | 233 +++++++++++++++++++++++++----------------
>>   include/linux/pci.h    |   7 ++
>>   include/linux/vgaarb.h |  27 +----
>>   4 files changed, 185 insertions(+), 112 deletions(-)
> I applied the rest of the patches on pci/vga for v6.5.
>
> I updated the commit logs and tweaked some of the patches.
>
> I squashed all the typo fixes together and added several more that I
> had done previously but not posted.  The diff between your original v2
> posting and the current pci/vga branch is attached.  Most of it is
> additional typo fixes, but if you look closely you'll see:
>
>    - The omission of the pci_get_class_masked() patches (in
>      vga_arbiter_add_pci_device(), pci_notify(), vga_arb_device_init())
>
>    - The tweaks I did to:
>
>        vga_update_device_decodes()
>        vga_client_register()
>        vga_arbiter_notify_clients()
>
> I dropped the Reviewed-bys from the typo fixes because I didn't want
> to extend them to everything that got squashed together.  Happy to add
> them back if anybody wants to look again.
>
> The branch is at https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/?h=vga
>
> Bjorn
>
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index f1c15aea868b..b4c138a6ec02 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -334,36 +334,6 @@ struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
>   }
>   EXPORT_SYMBOL(pci_get_device);
>   
> -/**
> - * pci_get_class_masked - begin or continue searching for a PCI device by class and mask
> - * @class: search for a PCI device with this class designation
> - * @from: Previous PCI device found in search, or %NULL for new search.
> - *
> - * Iterates through the list of known PCI devices.  If a PCI device is
> - * found with a matching @class, the reference count to the device is
> - * incremented and a pointer to its device structure is returned.
> - * Otherwise, %NULL is returned.
> - * A new search is initiated by passing %NULL as the @from argument.
> - * Otherwise if @from is not %NULL, searches continue from next device
> - * on the global list.  The reference count for @from is always decremented
> - * if it is not %NULL.
> - */
> -struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
> -				     struct pci_dev *from)
> -{
> -	struct pci_device_id id = {
> -		.vendor = PCI_ANY_ID,
> -		.device = PCI_ANY_ID,
> -		.subvendor = PCI_ANY_ID,
> -		.subdevice = PCI_ANY_ID,
> -		.class_mask = mask,
> -		.class = class,
> -	};
> -
> -	return pci_get_dev_by_id(&id, from);
> -}
> -EXPORT_SYMBOL(pci_get_class_masked);
> -
>   /**
>    * pci_get_class - begin or continue searching for a PCI device by class
>    * @class: search for a PCI device with this class designation
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index a2f6e0e6b634..5e6b1eb54c64 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -1,6 +1,6 @@
>   // SPDX-License-Identifier: MIT
>   /*
> - * vgaarb.c: Implements the VGA arbitration. For details refer to
> + * vgaarb.c: Implements VGA arbitration. For details refer to
>    * Documentation/gpu/vgaarbiter.rst
>    *
>    * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
> @@ -42,9 +42,9 @@ static void vga_arbiter_notify_clients(void);
>   struct vga_device {
>   	struct list_head list;
>   	struct pci_dev *pdev;
> -	unsigned int decodes;	/* what does it decodes */
> -	unsigned int owns;	/* what does it owns */
> -	unsigned int locks;	/* what does it locks */
> +	unsigned int decodes;		/* what it decodes */
> +	unsigned int owns;		/* what it owns */
> +	unsigned int locks;		/* what it locks */
>   	unsigned int io_lock_cnt;	/* legacy IO lock count */
>   	unsigned int mem_lock_cnt;	/* legacy MEM lock count */
>   	unsigned int io_norm_cnt;	/* normal IO count */
> @@ -116,20 +116,18 @@ static struct vga_device *vgadev_find(struct pci_dev *pdev)
>   /**
>    * 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.
> + * 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()...
> + * 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 arch 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 their 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)
>   {
> @@ -147,14 +145,13 @@ void vga_set_default_device(struct pci_dev *pdev)
>   }
>   
>   /**
> - * vga_remove_vgacon - deactivete vga console
> + * vga_remove_vgacon - deactivate VGA console
>    *
> - * Unbind and unregister vgacon in case pdev is the default vga
> - * device.  Can be called by gpu drivers on initialization to make
> - * sure vga register access done by vgacon will not disturb the
> - * device.
> + * Unbind and unregister vgacon in case pdev is the default VGA device.
> + * Can be called by GPU drivers on initialization to make sure VGA register
> + * access done by vgacon will not disturb the device.
>    *
> - * @pdev: pci device.
> + * @pdev: PCI device.
>    */
>   #if !defined(CONFIG_VGA_CONSOLE)
>   int vga_remove_vgacon(struct pci_dev *pdev)
> @@ -194,14 +191,15 @@ int vga_remove_vgacon(struct pci_dev *pdev)
>   EXPORT_SYMBOL(vga_remove_vgacon);
>   
>   /*
> - * If we don't ever use vgaarb, we should avoid turning off anything anywhere.
> - * Due to old X servers getting confused about the boot device not being VGA.
> + * If we don't ever use VGA arbitration, we should avoid turning off
> + * anything anywhere due to old X servers getting confused about the boot
> + * device not being VGA.
>    */
>   static void vga_check_first_use(void)
>   {
>   	/*
> -	 * We should inform all GPUs in the system that
> -	 * vgaarb has occurred and to try and disable resources if they can
> +	 * Inform all GPUs in the system that VGA arbitration has occurred
> +	 * so they can disable resources if possible.
>   	 */
>   	if (!vga_arbiter_used) {
>   		vga_arbiter_used = true;
> @@ -241,13 +239,13 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
>   
>   	/*
>   	 * We don't need to request a legacy resource, we just enable
> -	 * appropriate decoding and go
> +	 * appropriate decoding and go.
>   	 */
>   	legacy_wants = wants & VGA_RSRC_LEGACY_MASK;
>   	if (legacy_wants == 0)
>   		goto enable_them;
>   
> -	/* Ok, we don't, let's find out how we need to kick off */
> +	/* Ok, we don't, let's find out who we need to kick off */
>   	list_for_each_entry(conflict, &vga_list, list) {
>   		unsigned int lwants = legacy_wants;
>   		unsigned int change_bridge = 0;
> @@ -257,11 +255,11 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
>   			continue;
>   
>   		/*
> -		 * We have a possible conflict. before we go further, we must
> +		 * We have a possible conflict. Before we go further, we must
>   		 * check if we sit on the same bus as the conflicting device.
> -		 * if we don't, then we must tie both IO and MEM resources
> +		 * If we don't, then we must tie both IO and MEM resources
>   		 * together since there is only a single bit controlling
> -		 * VGA forwarding on P2P bridges
> +		 * VGA forwarding on P2P bridges.
>   		 */
>   		if (vgadev->pdev->bus != conflict->pdev->bus) {
>   			change_bridge = 1;
> @@ -270,14 +268,14 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
>   
>   		/*
>   		 * Check if the guy has a lock on the resource. If he does,
> -		 * return the conflicting entry
> +		 * return the conflicting entry.
>   		 */
>   		if (conflict->locks & lwants)
>   			return conflict;
>   
>   		/*
>   		 * Ok, now check if it owns the resource we want.  We can
> -		 * lock resources that are not decoded, therefore a device
> +		 * lock resources that are not decoded; therefore a device
>   		 * can own resources it doesn't decode.
>   		 */
>   		match = lwants & conflict->owns;
> @@ -285,8 +283,8 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
>   			continue;
>   
>   		/*
> -		 * Looks like he doesn't have a lock, we can steal
> -		 * them from him
> +		 * Looks like he doesn't have a lock, we can steal them
> +		 * from him.
>   		 */
>   
>   		flags = 0;
> @@ -321,7 +319,7 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
>   
>   enable_them:
>   	/*
> -	 * Ok dude, we got it, everybody conflicting has been disabled, let's
> +	 * Ok, we got it, everybody conflicting has been disabled, let's
>   	 * enable us.  Mark any bits in "owns" regardless of whether we
>   	 * decoded them.  We can lock resources we don't decode, therefore
>   	 * we must track them via "owns".
> @@ -364,8 +362,8 @@ static void __vga_put(struct vga_device *vgadev, unsigned int rsrc)
>   	vgaarb_dbg(dev, "%s\n", __func__);
>   
>   	/*
> -	 * Update our counters, and account for equivalent legacy resources
> -	 * if we decode them
> +	 * Update our counters and account for equivalent legacy resources
> +	 * if we decode them.
>   	 */
>   	if ((rsrc & VGA_RSRC_NORMAL_IO) && vgadev->io_norm_cnt > 0) {
>   		vgadev->io_norm_cnt--;
> @@ -384,7 +382,7 @@ static void __vga_put(struct vga_device *vgadev, unsigned int rsrc)
>   
>   	/*
>   	 * Just clear lock bits, we do lazy operations so we don't really
> -	 * have to bother about anything else at this point
> +	 * have to bother about anything else at this point.
>   	 */
>   	if (vgadev->io_lock_cnt == 0)
>   		vgadev->locks &= ~VGA_RSRC_LEGACY_IO;
> @@ -393,23 +391,23 @@ static void __vga_put(struct vga_device *vgadev, unsigned int rsrc)
>   
>   	/*
>   	 * Kick the wait queue in case somebody was waiting if we actually
> -	 * released something
> +	 * released something.
>   	 */
>   	if (old_locks != vgadev->locks)
>   		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
> + * vga_get - acquire & lock 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)
> + * Acquire VGA resources for the given card and mark those resources
> + * 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.
> + * 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
> @@ -441,7 +439,7 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
>   	int rc = 0;
>   
>   	vga_check_first_use();
> -	/* The one who calls us should check for this, but lets be sure... */
> +	/* The caller should check for this, but let's be sure */
>   	if (pdev == NULL)
>   		pdev = vga_default_device();
>   	if (pdev == NULL)
> @@ -461,11 +459,11 @@ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible)
>   			break;
>   
>   		/*
> -		 * We have a conflict, we wait until somebody kicks the
> +		 * We have a conflict; we wait until somebody kicks the
>   		 * work queue. Currently we have one work queue that we
>   		 * kick each time some resources are released, but it would
> -		 * be fairly easy to have a per device one so that we only
> -		 * need to attach to the conflicting device
> +		 * be fairly easy to have a per-device one so that we only
> +		 * need to attach to the conflicting device.
>   		 */
>   		init_waitqueue_entry(&wait, current);
>   		add_wait_queue(&vga_wait_queue, &wait);
> @@ -487,12 +485,12 @@ EXPORT_SYMBOL(vga_get);
>   
>   /**
>    * vga_tryget - try to acquire & lock legacy VGA resources
> - * @pdev: pci devivce of VGA card or NULL for system default
> + * @pdev: PCI device 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
> + * Perform the same operation as vga_get(), but return an error (-EBUSY)
> + * instead of blocking if the resources are already locked by another card.
> + * Can be called in any context.
>    *
>    * On success, release the VGA resource again with vga_put().
>    *
> @@ -508,7 +506,7 @@ static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
>   
>   	vga_check_first_use();
>   
> -	/* The one who calls us should check for this, but lets be sure... */
> +	/* The caller should check for this, but let's be sure */
>   	if (pdev == NULL)
>   		pdev = vga_default_device();
>   	if (pdev == NULL)
> @@ -528,20 +526,20 @@ static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
>   
>   /**
>    * 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
> + * @pdev: PCI device of VGA card or NULL for system default
> + * @rsrc: bit 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.
> + * Release resources previously locked by vga_get() or vga_tryget().  The
> + * resources aren't disabled right away, so that a subsequent 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;
>   	unsigned long flags;
>   
> -	/* The one who calls us should check for this, but lets be sure... */
> +	/* The caller should check for this, but let's be sure */
>   	if (pdev == NULL)
>   		pdev = vga_default_device();
>   	if (pdev == NULL)
> @@ -709,20 +707,20 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
>   		return;
>   	}
>   
> -	/* okay iterate the new devices bridge hierarachy */
> +	/* Iterate the new device's bridge hierarchy */
>   	new_bus = vgadev->pdev->bus;
>   	while (new_bus) {
>   		new_bridge = new_bus->self;
>   
> -		/* go through list of devices already registered */
> +		/* Go through list of devices already registered */
>   		list_for_each_entry(same_bridge_vgadev, &vga_list, list) {
>   			bus = same_bridge_vgadev->pdev->bus;
>   			bridge = bus->self;
>   
> -			/* See if the share a bridge with this device */
> +			/* See if it shares a bridge with this device */
>   			if (new_bridge == bridge) {
>   				/*
> -				 * If their direct parent bridge is the same
> +				 * If its direct parent bridge is the same
>   				 * as any bridge of this device then it can't
>   				 * be used for that device.
>   				 */
> @@ -730,10 +728,10 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
>   			}
>   
>   			/*
> -			 * Now iterate the previous devices bridge hierarchy.
> -			 * If the new devices parent bridge is in the other
> -			 * devices hierarchy then we can't use it to control
> -			 * this device
> +			 * Now iterate the previous device's bridge hierarchy.
> +			 * If the new device's parent bridge is in the other
> +			 * device's hierarchy, we can't use it to control this
> +			 * device.
>   			 */
>   			while (bus) {
>   				bridge = bus->self;
> @@ -754,10 +752,9 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
>   }
>   
>   /*
> - * Currently, we assume that the "initial" setup of the system is
> - * not sane, that is we come up with conflicting devices and let
> - * the arbiter's client decides if devices decodes or not legacy
> - * things.
> + * Currently, we assume that the "initial" setup of the system is not sane,
> + * that is, we come up with conflicting devices and let the arbiter's
> + * client decide if devices decodes legacy things or not.
>    */
>   static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
>   {
> @@ -767,12 +764,16 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
>   	struct pci_dev *bridge;
>   	u16 cmd;
>   
> +	/* Only deal with VGA class devices */
> +	if ((pdev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
> +		return false;
> +
>   	/* Allocate structure */
>   	vgadev = kzalloc(sizeof(struct vga_device), GFP_KERNEL);
>   	if (vgadev == NULL) {
>   		vgaarb_err(&pdev->dev, "failed to allocate VGA arbiter data\n");
>   		/*
> -		 * What to do on allocation failure ? For now, let's just do
> +		 * What to do on allocation failure? For now, let's just do
>   		 * nothing, I'm not sure there is anything saner to be done.
>   		 */
>   		return false;
> @@ -792,9 +793,10 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
>   
>   	/* By default, mark it as decoding */
>   	vga_decode_count++;
> +
>   	/*
>   	 * Mark that we "own" resources based on our enables, we will
> -	 * clear that below if the bridge isn't forwarding
> +	 * clear that below if the bridge isn't forwarding.
>   	 */
>   	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
>   	if (cmd & PCI_COMMAND_IO)
> @@ -874,7 +876,7 @@ static bool vga_arbiter_del_pci_device(struct pci_dev *pdev)
>   	return ret;
>   }
>   
> -/* This is called with the lock */
> +/* Called with the lock */
>   static void vga_update_device_decodes(struct vga_device *vgadev,
>   				      unsigned int new_decodes)
>   {
> @@ -885,8 +887,7 @@ static void vga_update_device_decodes(struct vga_device *vgadev,
>   
>   	vgadev->decodes = new_decodes;
>   
> -	vgaarb_info(dev,
> -		    "VGA decodes changed: olddecodes=%s,decodes=%s:owns=%s\n",
> +	vgaarb_info(dev, "VGA decodes changed: olddecodes=%s,decodes=%s:owns=%s\n",
>   		    vga_iostate_to_str(old_decodes),
>   		    vga_iostate_to_str(vgadev->decodes),
>   		    vga_iostate_to_str(vgadev->owns));
> @@ -932,9 +933,9 @@ static void __vga_set_legacy_decoding(struct pci_dev *pdev,
>   	vga_update_device_decodes(vgadev, decodes);
>   
>   	/*
> -	 * XXX if somebody is going from "doesn't decode" to "decodes" state
> -	 * here, additional care must be taken as we may have pending owner
> -	 * ship of non-legacy region ...
> +	 * XXX If somebody is going from "doesn't decode" to "decodes"
> +	 * state here, additional care must be taken as we may have pending
> +	 * ownership of non-legacy region.
>   	 */
>   bail:
>   	spin_unlock_irqrestore(&vga_lock, flags);
> @@ -942,10 +943,10 @@ static void __vga_set_legacy_decoding(struct pci_dev *pdev,
>   
>   /**
>    * vga_set_legacy_decoding
> - * @pdev: pci device of the VGA card
> + * @pdev: PCI device of the VGA card
>    * @decodes: bit mask of what legacy regions the card decodes
>    *
> - * Indicates to the arbiter if the card decodes legacy VGA IOs, legacy VGA
> + * Indicate 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
> @@ -959,44 +960,42 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>   
>   /**
>    * vga_client_register - register or unregister a VGA arbitration client
> - * @pdev: pci device of the VGA client
> - * @set_decode: vga decode change callback
> + * @pdev: PCI device of the VGA client
> + * @set_decode: VGA decode change callback
>    *
>    * Clients have two callback mechanisms they can use.
>    *
>    * @set_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.
> + * Rationale: we cannot disable VGA decode resources unconditionally
> + * because 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.
> + * Does not check whether a client for @pdev has been registered already.
>    *
> - * To unregister just call vga_client_unregister().
> + * To unregister, call vga_client_unregister().
>    *
>    * Returns: 0 on success, -ENODEV on failure
>    */
>   int vga_client_register(struct pci_dev *pdev,
>   		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
>   {
> -	int ret = -ENODEV;
> -	struct vga_device *vgadev;
>   	unsigned long flags;
> +	struct vga_device *vgadev;
>   
>   	spin_lock_irqsave(&vga_lock, flags);
>   	vgadev = vgadev_find(pdev);
> -	if (vgadev) {
> +	if (vgadev)
>   		vgadev->set_decode = set_decode;
> -		ret = 0;
> -	}
>   	spin_unlock_irqrestore(&vga_lock, flags);
> -
> -	return ret;
> +	if (!vgadev)
> +		return -ENODEV;
> +	return 0;
>   }
>   EXPORT_SYMBOL(vga_client_register);
>   
> @@ -1005,13 +1004,13 @@ EXPORT_SYMBOL(vga_client_register);
>    *
>    * Semantics is:
>    *
> - *  open       : open user instance of the arbitrer. by default, it's
> + *  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
> + *  close      : Close user instance, release locks
>    *
> - *  read       : return a string indicating the status of the target.
> - *                an IO state string is of the form {io,mem,io+mem,none},
> + *  read       : Return a string indicating the status of the target.
> + *                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
> @@ -1025,7 +1024,7 @@ EXPORT_SYMBOL(vga_client_register);
>    * write       : write a command to the arbiter. List of commands is:
>    *
>    *   target <card_ID>   : switch target to card <card_ID> (see below)
> - *   lock <io_state>    : acquires locks on target ("none" is invalid io_state)
> + *   lock <io_state>    : acquire locks on target ("none" is invalid io_state)
>    *   trylock <io_state> : non-blocking acquire locks on target
>    *   unlock <io_state>  : release locks on target
>    *   unlock all         : release all locks on target held by this user
> @@ -1042,23 +1041,21 @@ EXPORT_SYMBOL(vga_client_register);
>    * Note about locks:
>    *
>    * The driver keeps track of which user has what locks on which card. It
> - * supports stacking, like the kernel one. This complexifies the implementation
> + * supports stacking, like the kernel one. This complicates the implementation
>    * a bit, but makes the arbiter more tolerant to userspace problems and able
>    * to properly cleanup in all cases when a process dies.
>    * Currently, a max of 16 cards simultaneously can have locks issued from
>    * userspace for a given user (file descriptor instance) of the arbiter.
>    *
>    * If the device is hot-unplugged, there is a hook inside the module to notify
> - * they being added/removed in the system and automatically added/removed in
> + * it being added/removed in the system and automatically added/removed in
>    * the arbiter.
>    */
>   
>   #define MAX_USER_CARDS         CONFIG_VGA_ARB_MAX_GPUS
>   #define PCI_INVALID_CARD       ((struct pci_dev *)-1UL)
>   
> -/*
> - * Each user has an array of these, tracking which cards have locks
> - */
> +/* Each user has an array of these, tracking which cards have locks */
>   struct vga_arb_user_card {
>   	struct pci_dev *pdev;
>   	unsigned int mem_cnt;
> @@ -1077,9 +1074,8 @@ static DEFINE_SPINLOCK(vga_user_lock);
>   
>   
>   /*
> - * This function gets a string in the format: "PCI:domain:bus:dev.fn" and
> - * returns the respective values. If the string is not in this format,
> - * it returns 0.
> + * Take a string in the format: "PCI:domain:bus:dev.fn" and return the
> + * respective values. If the string is not in this format, return 0.
>    */
>   static int vga_pci_str_to_vars(char *buf, int count, unsigned int *domain,
>   			       unsigned int *bus, unsigned int *devfn)
> @@ -1111,7 +1107,7 @@ static ssize_t vga_arb_read(struct file *file, char __user *buf,
>   	if (lbuf == NULL)
>   		return -ENOMEM;
>   
> -	/* Protects vga_list */
> +	/* Protect vga_list */
>   	spin_lock_irqsave(&vga_lock, flags);
>   
>   	/* If we are targeting the default, use it */
> @@ -1126,15 +1122,15 @@ static ssize_t vga_arb_read(struct file *file, char __user *buf,
>   	vgadev = vgadev_find(pdev);
>   	if (vgadev == NULL) {
>   		/*
> -		 * Wow, it's not in the list, that shouldn't happen,
> -		 * let's fix us up and return invalid card
> +		 * Wow, it's not in the list, that shouldn't happen, let's
> +		 * fix us up and return invalid card.
>   		 */
>   		spin_unlock_irqrestore(&vga_lock, flags);
>   		len = sprintf(lbuf, "invalid");
>   		goto done;
>   	}
>   
> -	/* Fill the buffer with infos */
> +	/* Fill the buffer with info */
>   	len = snprintf(lbuf, 1024,
>   		       "count:%d,PCI:%s,decodes=%s,owns=%s,locks=%s(%u:%u)\n",
>   		       vga_decode_count, pci_name(pdev),
> @@ -1180,7 +1176,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf,
>   	if (copy_from_user(kbuf, buf, count))
>   		return -EFAULT;
>   	curr_pos = kbuf;
> -	kbuf[count] = '\0';	/* Just to make sure... */
> +	kbuf[count] = '\0';
>   
>   	if (strncmp(curr_pos, "lock ", 5) == 0) {
>   		curr_pos += 5;
> @@ -1205,7 +1201,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf,
>   
>   		vga_get_uninterruptible(pdev, io_state);
>   
> -		/* Update the client's locks lists... */
> +		/* Update the client's locks lists */
>   		for (i = 0; i < MAX_USER_CARDS; i++) {
>   			if (priv->cards[i].pdev == pdev) {
>   				if (io_state & VGA_RSRC_LEGACY_IO)
> @@ -1372,7 +1368,7 @@ static ssize_t vga_arb_write(struct file *file, const char __user *buf,
>   			vgaarb_dbg(&pdev->dev, "maximum user cards (%d) number reached, ignoring this one!\n",
>   				MAX_USER_CARDS);
>   			pci_dev_put(pdev);
> -			/* XXX: which value to return? */
> +			/* XXX: Which value to return? */
>   			ret_val =  -ENOMEM;
>   			goto done;
>   		}
> @@ -1433,7 +1429,7 @@ static int vga_arb_open(struct inode *inode, struct file *file)
>   	list_add(&priv->list, &vga_user_list);
>   	spin_unlock_irqrestore(&vga_user_lock, flags);
>   
> -	/* Set the client' lists of locks */
> +	/* Set the client's lists of locks */
>   	priv->target = vga_default_device(); /* Maybe this is still null! */
>   	priv->cards[0].pdev = priv->target;
>   	priv->cards[0].io_cnt = 0;
> @@ -1472,68 +1468,32 @@ static int vga_arb_release(struct inode *inode, struct file *file)
>   }
>   
>   /*
> - * Callback any registered clients to let them know we have a
> - * change in VGA cards
> + * Callback any registered clients to let them know we have a change in VGA
> + * cards.
>    */
>   static void vga_arbiter_notify_clients(void)
>   {
>   	struct vga_device *vgadev;
>   	unsigned long flags;
> -	bool state;
> +	unsigned int new_decodes;
> +	bool new_state;
>   
>   	if (!vga_arbiter_used)
>   		return;
>   
> -	state = (vga_count > 1) ? false : true;
> +	new_state = (vga_count > 1) ? false : true;
>   
>   	spin_lock_irqsave(&vga_lock, flags);
>   	list_for_each_entry(vgadev, &vga_list, list) {
>   		if (vgadev->set_decode) {
> -			unsigned int decodes;
> -
> -			decodes = vgadev->set_decode(vgadev->pdev, state);
> -			vga_update_device_decodes(vgadev, decodes);
> +			new_decodes = vgadev->set_decode(vgadev->pdev,
> +							 new_state);
> +			vga_update_device_decodes(vgadev, new_decodes);
>   		}
>   	}
>   	spin_unlock_irqrestore(&vga_lock, flags);
>   }
>   
> -/*
> - * The PCI Class Code spec implies that only VGA devices with programming
> - * interface 0x00 can depend on the legacy VGA address range. VGA devices
> - * with programming interface 0x01 are 8514-compatible controllers. Since
> - * VGA devices with programming interface 0x00 is VGA compatible, the 'vga'
> - * suffix here should refer to the VGA-compatible devices after a strict
> - * reading of that specification. But considering the fact that there
> - * probably don't has a 8514-compatible controller that could be used with
> - * upstream kernel anymore, we would like to just ignore the programming
> - * interface byte.
> - *
> - * Besides, there do exist non VGA-compatible display controllers in the
> - * world and hardware vendors may abandon the old VGA standard someday.
> - * The meaning of 'vga' suffix here may change to evolve with time.
> - *
> - * A strict understanding of 'vga' certainly should be VGA-compatible, While
> - * a relaxed understanding of 'vga' would be PCI devices that are able to
> - * display. Currently, we just keep aligned to the previous behavior.
> - * Deal with VGA class devices.
> - */
> -static bool pci_dev_is_vga(struct pci_dev *pdev)
> -{
> -	if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> -		return true;
> -
> -	/*
> -	 * The PCI_CLASS_NOT_DEFINED_VGA is defined to provide backward
> -	 * compatibility for devices that were built before the class code
> -	 * field was defined.
> -	 */
> -	if ((pdev->class >> 8) == PCI_CLASS_NOT_DEFINED_VGA)
> -		return true;
> -
> -	return false;
> -}
> -
>   static int pci_notify(struct notifier_block *nb, unsigned long action,
>   		      void *data)
>   {
> @@ -1543,9 +1503,6 @@ static int pci_notify(struct notifier_block *nb, unsigned long action,
>   
>   	vgaarb_dbg(dev, "%s\n", __func__);
>   
> -	if (!pci_dev_is_vga(pdev))
> -		return 0;
> -
>   	/*
>   	 * For now, we're only interested in devices added and removed.
>   	 * I didn't test this thing here, so someone needs to double check
> @@ -1580,8 +1537,8 @@ static struct miscdevice vga_arb_device = {
>   
>   static int __init vga_arb_device_init(void)
>   {
> -	struct pci_dev *pdev = NULL;
>   	int rc;
> +	struct pci_dev *pdev;
>   
>   	rc = misc_register(&vga_arb_device);
>   	if (rc < 0)
> @@ -1589,22 +1546,12 @@ static int __init vga_arb_device_init(void)
>   
>   	bus_register_notifier(&pci_bus_type, &pci_notifier);
>   
> -	/*
> -	 * We add all PCI devices satisfying VGA class in the arbiter
> -	 * by default, but we ignore the programming interface byte
> -	 * intentionally.
> -	 */
> -	do {
> -		pdev = pci_get_class_masked(PCI_CLASS_DISPLAY_VGA << 8, 0xFFFF00, pdev);
> -		if (pdev && pci_dev_is_vga(pdev))
> -			vga_arbiter_add_pci_device(pdev);
> -	} while (pdev);
> -
> -	do {
> -		pdev = pci_get_class_masked(PCI_CLASS_NOT_DEFINED_VGA << 8, 0xFFFF00, pdev);
> -		if (pdev && pci_dev_is_vga(pdev))
> -			vga_arbiter_add_pci_device(pdev);
> -	} while (pdev);
> +	/* Add all VGA class PCI devices by default */
> +	pdev = NULL;
> +	while ((pdev =
> +		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
> +			       PCI_ANY_ID, pdev)) != NULL)
> +		vga_arbiter_add_pci_device(pdev);
>   
>   	pr_info("loaded\n");
>   	return rc;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 14dc5ab4a1d2..c69a2cc1f412 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1180,9 +1180,6 @@ struct pci_dev *pci_get_slot(struct pci_bus *bus, unsigned int devfn);
>   struct pci_dev *pci_get_domain_bus_and_slot(int domain, unsigned int bus,
>   					    unsigned int devfn);
>   struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from);
> -struct pci_dev *pci_get_class_masked(unsigned int class, unsigned int mask,
> -				     struct pci_dev *from);
> -
>   int pci_dev_present(const struct pci_device_id *ids);
>   
>   int pci_bus_read_config_byte(struct pci_bus *bus, unsigned int devfn,
> @@ -1898,10 +1895,6 @@ static inline struct pci_dev *pci_get_class(unsigned int class,
>   					    struct pci_dev *from)
>   { return NULL; }
>   
> -static inline struct pci_dev *pci_get_class_masked(unsigned int class,
> -						   unsigned int mask,
> -						   struct pci_dev *from)
> -{ return NULL; }
>   
>   static inline int pci_dev_present(const struct pci_device_id *ids)
>   { return 0; }