Re: [PATCH v6 2/8] PCI/VGA: Deal only with VGA class devices

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 6/12/2023 2:25 PM, Sui Jingfeng wrote:
> From: Sui Jingfeng <suijingfeng@loongson.cn>
>
> Deal only with the VGA devcie(pdev->class == 0x0300), so replace the
> pci_get_subsys() function with pci_get_class(). Filter the non-PCI display
> device(pdev->class != 0x0300) out. There no need to process the non-display
> PCI device.
>
> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
> ---
This also means that deleting a PCI device no longer needs
to walk the list.

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>

>   drivers/pci/vgaarb.c | 22 ++++++++++++----------
>   1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index c1bc6c983932..22a505e877dc 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -754,10 +754,6 @@ 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) {
> @@ -1500,7 +1496,9 @@ static int pci_notify(struct notifier_block *nb, unsigned long action,
>   	struct pci_dev *pdev = to_pci_dev(dev);
>   	bool notify = false;
>   
> -	vgaarb_dbg(dev, "%s\n", __func__);
> +	/* Only deal with VGA class devices */
> +	if (pdev->class != PCI_CLASS_DISPLAY_VGA << 8)
> +		return 0;
>   
>   	/* For now we're only intereted in devices added and removed. I didn't
>   	 * test this thing here, so someone needs to double check for the
> @@ -1510,6 +1508,8 @@ static int pci_notify(struct notifier_block *nb, unsigned long action,
>   	else if (action == BUS_NOTIFY_DEL_DEVICE)
>   		notify = vga_arbiter_del_pci_device(pdev);
>   
> +	vgaarb_dbg(dev, "%s: action = %lu\n", __func__, action);
> +
>   	if (notify)
>   		vga_arbiter_notify_clients();
>   	return 0;
> @@ -1534,8 +1534,8 @@ 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)
> @@ -1545,11 +1545,13 @@ static int __init vga_arb_device_init(void)
>   
>   	/* We add all PCI devices satisfying VGA class in the arbiter by
>   	 * default */
> -	pdev = NULL;
> -	while ((pdev =
> -		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
> -			       PCI_ANY_ID, pdev)) != NULL)
> +	while (1) {
> +		pdev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev);
> +		if (!pdev)
> +			break;
> +
>   		vga_arbiter_add_pci_device(pdev);
> +	}
>   
>   	pr_info("loaded\n");
>   	return rc;