Re: [PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe path

[Jason Gunthorpe]

On Fri, Feb 28, 2025 at 03:46:33PM +0000, Robin Murphy wrote:
> +	if (!dev->driver && dev->bus->dma_configure) {
> +		mutex_unlock(&iommu_probe_device_lock);
> +		dev->bus->dma_configure(dev);
> +		mutex_lock(&iommu_probe_device_lock);
> +	}

I think it would be very nice to get rid of the lock/unlock.. It makes
me nervous that we continue on assuming dev->iommu was freshly
allocated..

 setup the dev->iommu partially, then drop the lock.

There is only one other caller in:

static int really_probe(struct device *dev, const struct device_driver *drv)
{
	if (dev->bus->dma_configure) {
		ret = dev->bus->dma_configure(dev);
		if (ret)
			goto pinctrl_bind_failed;
	}

Is it feasible to make it so the caller has to hold the
iommu_probe_device_lock prior to calling the op?

That would require moving the locking inside of_dma_configure to less
inside, and using a new iommu_probe_device() wrapper.

However, if you plan to turn this inside out soonish then it would not
be worth the bother.

Anyhow:

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason