linux-kernel - Re: [-next 4/5] drm/virgpu: Switch to pci_is

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Message-ID: <20231005221049.GA793091@bhelgaas>
Date:   Thu, 5 Oct 2023 17:10:49 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc:     Sui Jingfeng <suijingfeng@...ngson.cn>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        David Airlie <airlied@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [-next 4/5] drm/virgpu: Switch to pci_is_vga()

On Thu, Oct 05, 2023 at 04:57:14PM -0500, Bjorn Helgaas wrote:
> In subject: "drm/virtio" to match previous history.
> 
> On Wed, Aug 30, 2023 at 07:15:31PM +0800, Sui Jingfeng wrote:
> > From: Sui Jingfeng <suijingfeng@...ngson.cn>
> > 
> > Should be no functional change, just for cleanup purpose.
> > 
> > Cc: David Airlie <airlied@...hat.com>
> > Cc: Gerd Hoffmann <kraxel@...hat.com>
> > Cc: Gurchetan Singh <gurchetansingh@...omium.org>
> > Cc: Chia-I Wu <olvaffe@...il.com>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> > ---
> >  drivers/gpu/drm/virtio/virtgpu_drv.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> > index add075681e18..3a368304475a 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> > @@ -51,7 +51,7 @@ static int virtio_gpu_pci_quirk(struct drm_device *dev)
> >  {
> >  	struct pci_dev *pdev = to_pci_dev(dev->dev);
> >  	const char *pname = dev_name(&pdev->dev);
> > -	bool vga = (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA;
> > +	bool vga = pci_is_vga(pdev);
> 
> This *is* a functional change: Previously "vga" was only true for
> PCI_CLASS_DISPLAY_VGA (0x0300).  Now it will be true for both
> PCI_CLASS_DISPLAY_VGA (0x0300) and PCI_CLASS_DISPLAY_OTHER (0x0380).

Oops, sorry, my mistake here.  I meant PCI_CLASS_NOT_DEFINED_VGA, not
PCI_CLASS_DISPLAY_OTHER.  pci_is_vga() is true for either of:

  PCI_CLASS_DISPLAY_VGA       0x0300
  PCI_CLASS_NOT_DEFINED_VGA   0x0001

(PCI_CLASS_NOT_DEFINED_VGA is defined in the PCI Code and Assignment
spec r1.15, sec 1.1; PCI_CLASS_DISPLAY_VGA is sec 1.4.)

> Is that desirable?  I can't tell.  Maybe the GPU folks will chime in.
> 
> >  	int ret;
> >  
> >  	DRM_INFO("pci: %s detected at %s\n",
> > -- 
> > 2.34.1
> >