Re: [PATCH 1/2] ACPI: Get acpi_device's parent from the parent field

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Nov 09, 2021 at 01:19:34PM +0200, Sakari Ailus wrote:
> Printk modifier %pfw is used to print the full path of the device name.
> This is obtained device by device until a device no longer has a parent.
> 
> On ACPI getting the parent fwnode is done by calling acpi_get_parent()
> which tries to down() a semaphore. But local IRQs are now disabled in
> vprintk_store() before the mutex is acquired. This is obviously a problem.
> 
> Luckily struct device, embedded in struct acpi_device, has a parent field
> already. Use that field to get the parent instead of relying on
> acpi_get_parent().

Thanks, with the below addressed
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Fixes: 3bd32d6a2ee6 ("lib/vsprintf: Add %pfw conversion specifier for printing fwnode names")
> Cc: stable@vger.kernel.org # v5.5+
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  drivers/acpi/property.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index e312ebaed8db4..dc97711ba8081 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -1089,16 +1089,14 @@ struct fwnode_handle *acpi_node_get_parent(const struct fwnode_handle *fwnode)
>  	if (is_acpi_data_node(fwnode)) {
>  		/* All data nodes have parent pointer so just return that */
>  		return to_acpi_data_node(fwnode)->parent;

...

> -	} else if (is_acpi_device_node(fwnode)) {
> +	}

> +	if (is_acpi_device_node(fwnode)) {

Unneeded change. Yes I know that 'else' here can be skipped. But in such cases
it's a trade-off between changes, code readability and maintenance. Since here
it's a fix, backporting concerns are also play role.

> +		struct device *dev =
> +			to_acpi_device_node(fwnode)->dev.parent;

We are not so strict in terms of line length, code will be better
if this is located on one line.

> -			if (!acpi_bus_get_device(parent_handle, &adev))
> -				return acpi_fwnode_handle(adev);
> -		}
> +		if (dev)
> +			return acpi_fwnode_handle(to_acpi_device(dev));
>  	}
>  
>  	return NULL;
> -- 
> 2.30.2
> 

-- 
With Best Regards,
Andy Shevchenko