linux-kernel - Re: [Intel-gfx] [PATCH v3 3/4] PCI/VGA: only deal with VGA class devices

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Message-ID: <20230608191221.GA1209912@bhelgaas>
Date:   Thu, 8 Jun 2023 14:12:21 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sui Jingfeng <15330273260@....cn>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian Konig <christian.koenig@....com>,
        Pan Xinhui <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Hawking Zhang <Hawking.Zhang@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Lijo Lazar <lijo.lazar@....com>,
        YiPeng Chai <YiPeng.Chai@....com>,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Somalapuram Amaranath <Amaranath.Somalapuram@....com>,
        Bokun Zhang <Bokun.Zhang@....com>,
        Ville Syrjala <ville.syrjala@...ux.intel.com>,
        Li Yi <liyi@...ngson.cn>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Abhishek Sahu <abhsahu@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>, kvm@...r.kernel.org,
        nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        loongson-kernel@...ts.loongnix.cn, amd-gfx@...ts.freedesktop.org,
        linux-pci@...r.kernel.org
Subject: Re: [Intel-gfx] [PATCH v3 3/4] PCI/VGA: only deal with VGA class
 devices

Start with verb and capitalize to match ("Deal only with ...")

On Thu, Jun 08, 2023 at 07:43:21PM +0800, Sui Jingfeng wrote:
> From: Sui Jingfeng <suijingfeng@...ngson.cn>
> 
> vgaarb only deal with the VGA devcie(pdev->class == 0x0300), so replace the
> pci_get_subsys() function with pci_get_class(). Filter the non pci display
> device out. There no need to process the non display PCI device.

s/non pci/non-PCI/
s/non display/non-display/

This is fine, and I'll merge this, but someday I would like to get rid
of the bus_register_notifier() and call vga_arbiter_add_pci_device()
and vga_arbiter_del_pci_device() directly from the PCI core.

Or if you wanted to do that now, that would be even better :)

Bjorn

> Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> ---
>  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 7f0347f4f6fd..b0bf4952a95d 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -756,10 +756,6 @@ 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) {
> @@ -1499,7 +1495,9 @@ 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 >> 8) != PCI_CLASS_DISPLAY_VGA)
> +		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
> @@ -1509,6 +1507,8 @@ 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;
> @@ -1533,8 +1533,8 @@ 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;
> -- 
> 2.25.1
>