Re: [PATCH v3 8/8] drm/vkms: convert to use faux_device

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Feb 06, 2025 at 03:03:41PM -0500, Lyude Paul wrote:
> Lol, I wrote up a patch for this last night but it looks like you got here
> first :P
> 
> On Thu, 2025-02-06 at 18:38 +0100, Greg Kroah-Hartman wrote:
> > The vkms driver does not need to create a platform device, as there is
> > no real platform resources associated it,  it only did so because it was
> > simple to do that in order to get a device to use for resource
> > management of drm resources.  Change the driver to use the faux device
> > instead as this is NOT a real platform device.
> > 
> > Cc: Louis Chauvet <louis.chauvet@bootlin.com>
> > Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
> > Cc: Simona Vetter <simona@ffwll.ch>
> > Cc: Melissa Wen <melissa.srw@gmail.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: David Airlie <airlied@gmail.com>
> > Cc: dri-devel@lists.freedesktop.org
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> >  v3: new patch in the series.  For an example of the api working, does
> >      not have to be merged at this time, but I can take it if the
> >      maintainers give an ack.
> >  drivers/gpu/drm/vkms/vkms_drv.c | 28 ++++++++++++++--------------
> >  drivers/gpu/drm/vkms/vkms_drv.h |  4 ++--
> >  2 files changed, 16 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > index e0409aba9349..b1269f984886 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > @@ -10,7 +10,7 @@
> >   */
> >  
> >  #include <linux/module.h>
> > -#include <linux/platform_device.h>
> > +#include <linux/device/faux.h>
> >  #include <linux/dma-mapping.h>
> >  
> >  #include <drm/clients/drm_client_setup.h>
> > @@ -177,25 +177,25 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
> >  static int vkms_create(struct vkms_config *config)
> >  {
> >  	int ret;
> > -	struct platform_device *pdev;
> > +	struct faux_device *fdev;
> >  	struct vkms_device *vkms_device;
> >  
> > -	pdev = platform_device_register_simple(DRIVER_NAME, -1, NULL, 0);
> > -	if (IS_ERR(pdev))
> > -		return PTR_ERR(pdev);
> > +	fdev = faux_device_create(DRIVER_NAME, NULL);
> > +	if (!fdev)
> > +		return -ENODEV;
> >  
> > -	if (!devres_open_group(&pdev->dev, NULL, GFP_KERNEL)) {
> > +	if (!devres_open_group(&fdev->dev, NULL, GFP_KERNEL)) {
> >  		ret = -ENOMEM;
> >  		goto out_unregister;
> >  	}
> >  
> > -	vkms_device = devm_drm_dev_alloc(&pdev->dev, &vkms_driver,
> > +	vkms_device = devm_drm_dev_alloc(&fdev->dev, &vkms_driver,
> >  					 struct vkms_device, drm);
> >  	if (IS_ERR(vkms_device)) {
> >  		ret = PTR_ERR(vkms_device);
> >  		goto out_devres;
> >  	}
> > -	vkms_device->platform = pdev;
> > +	vkms_device->faux_dev = fdev;
> >  	vkms_device->config = config;
> >  	config->dev = vkms_device;
> >  
> > @@ -229,9 +229,9 @@ static int vkms_create(struct vkms_config *config)
> >  	return 0;
> >  
> >  out_devres:
> > -	devres_release_group(&pdev->dev, NULL);
> > +	devres_release_group(&fdev->dev, NULL);
> >  out_unregister:
> > -	platform_device_unregister(pdev);
> > +	faux_device_destroy(fdev);
> >  	return ret;
> >  }
> >  
> > @@ -259,19 +259,19 @@ static int __init vkms_init(void)
> >  
> >  static void vkms_destroy(struct vkms_config *config)
> >  {
> > -	struct platform_device *pdev;
> > +	struct faux_device *fdev;
> >  
> >  	if (!config->dev) {
> >  		DRM_INFO("vkms_device is NULL.\n");
> >  		return;
> >  	}
> >  
> > -	pdev = config->dev->platform;
> > +	fdev = config->dev->faux_dev;
> >  
> >  	drm_dev_unregister(&config->dev->drm);
> >  	drm_atomic_helper_shutdown(&config->dev->drm);
> > -	devres_release_group(&pdev->dev, NULL);
> > -	platform_device_unregister(pdev);
> > +	devres_release_group(&fdev->dev, NULL);
> > +	faux_device_destroy(fdev);
> >  
> >  	config->dev = NULL;
> >  }
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index 00541eff3d1b..4668b0e29a84 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -209,13 +209,13 @@ struct vkms_config {
> >   * struct vkms_device - Description of a VKMS device
> >   *
> >   * @drm - Base device in DRM
> > - * @platform - Associated platform device
> > + * @faux_dev- Associated faux device
> 
> Small nitpick - you dropped the space on the - here by mistake

Ick, good catch.

> With that fixed:
> 
> Reviewed-by: Lyude Paul <lyude@redhat.com>

Thanks for the review!

greg k-h