Re: [PATCH v4 09/23] cxl: Add helper function to retrieve ACPI handle of CXL root device

[Dave Jiang <dave.jiang@intel.com>]

On 4/20/23 5:06 AM, Jonathan Cameron wrote:
> On Wed, 19 Apr 2023 13:21:55 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
>> Provide a helper to find the ACPI0017 device in order to issue the _DSM.
>> The helper will take the 'struct device' from a cxl_port and iterate until
>> the root device is reached. The ACPI handle will be returned from the root
>> device.
>>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> Question inline.  If the answer is no then this looks fine to me.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> 
>> +/**
>> + * cxl_acpi_get_rootdev_handle - get the ACPI handle of the CXL root device
>> + * @dev: 'struct device' to start searching from. Should be from cxl_port->dev.
>> + *
>> + * Return: acpi_handle on success, errptr of errno on error.
>> + *
>> + * Looks for the ACPI0017 device and return the ACPI handle
>> + **/
> 
> Could we implement this in terms of find_cxl_root()?  I think that will
> end up giving you the same device though I haven't tested it.

Yes I can simplify this. Thanks.

> 
>> +acpi_handle cxl_acpi_get_rootdev_handle(struct device *dev)
>> +{
>> +	struct device *itr = dev;
>> +	struct device *root_dev;
>> +	acpi_handle handle;
>> +
>> +	if (!dev)
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	while (itr->parent) {
>> +		root_dev = itr;
>> +		itr = itr->parent;
>> +	}
>> +
>> +	if (!dev_is_platform(root_dev))
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	handle = ACPI_HANDLE(root_dev);
>> +	if (!handle)
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	return handle;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_acpi_get_rootdev_handle, CXL);
> 
>