linux-kernel - Re: [PATCH v4 8/9] drm/vgem/vgem_drv convert to use faux

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Message-ID: <0e6817b1-d52e-407f-bdb9-93919f849edc@suse.de>
Date: Tue, 25 Feb 2025 12:38:54 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-kernel@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Liam Girdwood <lgirdwood@...il.com>, Lukas Wunner <lukas@...ner.de>,
 Mark Brown <broonie@...nel.org>, Maíra Canal
 <mairacanal@...eup.net>, Robin Murphy <robin.murphy@....com>,
 Simona Vetter <simona.vetter@...ll.ch>, Zijun Hu <quic_zijuhu@...cinc.com>,
 linux-usb@...r.kernel.org, rust-for-linux@...r.kernel.org,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v4 8/9] drm/vgem/vgem_drv convert to use faux_device

Hi

Am 10.02.25 um 13:30 schrieb Greg Kroah-Hartman:
> The vgem 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: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
> Cc: Maxime Ripard <mripard@...nel.org>
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: David Airlie <airlied@...il.com>
> Cc: Simona Vetter <simona@...ll.ch>
> Cc: dri-devel@...ts.freedesktop.org
> Reviewed-by: Lyude Paul <lyude@...hat.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

Should this patch be merged through DRM trees?

Best regards
Thomas

> ---
> v4: - api tweaked due to parent pointer added to faux_device create
>        function.
>   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/vgem/vgem_drv.c | 30 +++++++++++++++---------------
>   1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 2752ab4f1c97..260c64733972 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -32,7 +32,7 @@
>   
>   #include <linux/dma-buf.h>
>   #include <linux/module.h>
> -#include <linux/platform_device.h>
> +#include <linux/device/faux.h>
>   #include <linux/shmem_fs.h>
>   #include <linux/vmalloc.h>
>   
> @@ -52,7 +52,7 @@
>   
>   static struct vgem_device {
>   	struct drm_device drm;
> -	struct platform_device *platform;
> +	struct faux_device *faux_dev;
>   } *vgem_device;
>   
>   static int vgem_open(struct drm_device *dev, struct drm_file *file)
> @@ -127,27 +127,27 @@ static const struct drm_driver vgem_driver = {
>   static int __init vgem_init(void)
>   {
>   	int ret;
> -	struct platform_device *pdev;
> +	struct faux_device *fdev;
>   
> -	pdev = platform_device_register_simple("vgem", -1, NULL, 0);
> -	if (IS_ERR(pdev))
> -		return PTR_ERR(pdev);
> +	fdev = faux_device_create("vgem", NULL, 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;
>   	}
>   
> -	dma_coerce_mask_and_coherent(&pdev->dev,
> +	dma_coerce_mask_and_coherent(&fdev->dev,
>   				     DMA_BIT_MASK(64));
>   
> -	vgem_device = devm_drm_dev_alloc(&pdev->dev, &vgem_driver,
> +	vgem_device = devm_drm_dev_alloc(&fdev->dev, &vgem_driver,
>   					 struct vgem_device, drm);
>   	if (IS_ERR(vgem_device)) {
>   		ret = PTR_ERR(vgem_device);
>   		goto out_devres;
>   	}
> -	vgem_device->platform = pdev;
> +	vgem_device->faux_dev = fdev;
>   
>   	/* Final step: expose the device/driver to userspace */
>   	ret = drm_dev_register(&vgem_device->drm, 0);
> @@ -157,19 +157,19 @@ static int __init vgem_init(void)
>   	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;
>   }
>   
>   static void __exit vgem_exit(void)
>   {
> -	struct platform_device *pdev = vgem_device->platform;
> +	struct faux_device *fdev = vgem_device->faux_dev;
>   
>   	drm_dev_unregister(&vgem_device->drm);
> -	devres_release_group(&pdev->dev, NULL);
> -	platform_device_unregister(pdev);
> +	devres_release_group(&fdev->dev, NULL);
> +	faux_device_destroy(fdev);
>   }
>   
>   module_init(vgem_init);

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)