Re: [PATCH] drm/loongson: clean up KMS polling on probe failure

[Icenowy Zheng <zhengxingda@iscas.ac.cn>]

在 2026-05-12二的 02:01 +0900，Myeonghun Pak写道：
> lsdc_pci_probe() initializes KMS polling before setting up vblank
> support,
> requesting the IRQ and registering the DRM device. If any of those
> later
> steps fails, probe returns without finalizing polling. The remove
> path has
> the same lifetime gap when tearing down a successfully registered
> device.
> 
> Route those probe failures through a poll cleanup label. Also
> finalize
> polling from remove before unregistering the DRM device.

Interesting, but it looks like a `drmm_kms_helper_poll_init` function
exists (while rarely used).

Maybe it's better to switch to this? Or maybe there's some reason not
to use this?

Thanks,
Icenowy

> 
> This issue was identified during our ongoing static-analysis research
> while
> reviewing kernel code.
> 
> Fixes: f39db26c5428 ("drm: Add kms driver for loongson display
> controller")
> Cc: stable@vger.kernel.org
> Co-developed-by: Ijae Kim <ae878000@gmail.com>
> Signed-off-by: Ijae Kim <ae878000@gmail.com>
> Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
> ---
>  drivers/gpu/drm/loongson/lsdc_drv.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_drv.c
> b/drivers/gpu/drm/loongson/lsdc_drv.c
> index abf5bf68ee..3db1f8690a 100644
> --- a/drivers/gpu/drm/loongson/lsdc_drv.c
> +++ b/drivers/gpu/drm/loongson/lsdc_drv.c
> @@ -297,7 +297,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  	if (loongson_vblank) {
>  		ret = drm_vblank_init(ddev, descp->num_of_crtc);
>  		if (ret)
> -			return ret;
> +			goto err_poll_fini;
>  
>  		ret = devm_request_irq(&pdev->dev, pdev->irq,
>  				       descp->funcs->irq_handler,
> @@ -305,7 +305,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  				       dev_name(&pdev->dev), ddev);
>  		if (ret) {
>  			drm_err(ddev, "Failed to register interrupt:
> %d\n", ret);
> -			return ret;
> +			goto err_poll_fini;
>  		}
>  
>  		drm_info(ddev, "registered irq: %u\n", pdev->irq);
> @@ -313,17 +313,22 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  
>  	ret = drm_dev_register(ddev, 0);
>  	if (ret)
> -		return ret;
> +		goto err_poll_fini;
>  
>  	drm_client_setup(ddev, NULL);
>  
>  	return 0;
> +
> +err_poll_fini:
> +	drm_kms_helper_poll_fini(ddev);
> +	return ret;
>  }
>  
>  static void lsdc_pci_remove(struct pci_dev *pdev)
>  {
>  	struct drm_device *ddev = pci_get_drvdata(pdev);
>  
> +	drm_kms_helper_poll_fini(ddev);
>  	drm_dev_unregister(ddev);
>  	drm_atomic_helper_shutdown(ddev);
>  }