Re: [PATCH v4 8/9] drm/vgem/vgem_drv convert to use faux_device

Thomas Zimmermann
2025-02-26T08:18:38Z

Am 25.02.25 um 12:38 schrieb Thomas Zimmermann:
> 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@linux.intel.com>
>> Cc: Maxime Ripard <mripard@kernel.org>
>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
>> Cc: David Airlie <airlied@gmail.com>
>> Cc: Simona Vetter <simona@ffwll.ch>
>> Cc: dri-devel@lists.freedesktop.org
>> Reviewed-by: Lyude Paul <lyude@redhat.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
>
> Should this patch be merged through DRM trees?

Louis mentioned that the vkms patch will goes through DRM. If no one
objects, I'll merge this patch there as well.

Best regards
Thomas

>
> 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)