Re: [PATCH 2/6] gpu: host1x: Avoid double device_add when clients already present

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The patch prevents a double `device_add()` on the success path, but causes a forbidden second `device_add()` call if the first attempt fails.
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commit ece8de02ea1a088261ec6c5d40e683d0804f1957
Author: Mikko Perttunen <mperttunen@nvidia.com>

gpu: host1x: Avoid double device_add when clients already present

This commit fixes an issue in host1x_device_add where device_add is called
twice if all subdevs are matched and moved to the active list. It prevents
the second call by checking a registered flag before invoking device_add at
the end of the function.

> diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c
> index f814eb4941c02..fe4af98e8fc68 100644
> --- a/drivers/gpu/host1x/bus.c
> +++ b/drivers/gpu/host1x/bus.c

[ ... ]

> @@ -508,7 +508,7 @@ static int host1x_device_add(struct host1x *host1x,
>  	 * Add device even if there are no subdevs to ensure syncpoint functionality
>  	 * is available regardless of whether any engine subdevices are present
>  	 */
> -	if (list_empty(&device->subdevs)) {
> +	if (list_empty(&device->subdevs) && !device->registered) {

[Severity: High]
Does this cause a forbidden second device_add() call if the first attempt
fails during the subdevice registration flow?

If device_add() is called earlier during host1x_subdev_register() and fails,
device->registered remains false. The execution then continues to this final
block in host1x_device_add(). 

Since list_empty(&device->subdevs) could evaluate to true and 
!device->registered is also true, won't this trigger an immediate second
device_add() on the identically failed structure?

>  		err = device_add(&device->dev);
>  		if (err < 0)
>  			dev_err(&device->dev, "failed to add device: %d\n", err);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260609-b4-host1x-small-fixes-a-v1-0-7c1131c0b3ad@nvidia.com?part=2