Re: [PATCH v4] driver core: Add sysfs support for physical location of a device

[Greg Kroah-Hartman]

On Wed, Mar 09, 2022 at 11:06:07PM +0000, Won Chung wrote:
> When ACPI table includes _PLD fields for a device, create a new
> directory (physical_location) in sysfs to share _PLD fields.
> 
> Currently without PLD information, when there are multiple of same
> devices, it is hard to distinguish which device corresponds to which
> physical device at which location. For example, when there are two Type
> C connectors, it is hard to find out which connector corresponds to the
> Type C port on the left panel versus the Type C port on the right panel.
> With PLD information provided, we can determine which specific device at
> which location is doing what.
> 
> _PLD output includes much more fields, but only generic fields are added
> and exposed to sysfs, so that non-ACPI devices can also support it in
> the future. The minimal generic fields needed for locating a device are
> the following.
> - panel
> - vertical_position
> - horizontal_position
> - dock
> - lid
> 
> Signed-off-by: Won Chung <wonchung@xxxxxxxxxx>
> ---
> 
> Changes from v3
> - Move dev_add_physical_location() and dev_attr_physical_location_group
>   to driver/base/physical_location.h.
> - Use pointer and reorder physical_location in struct device to pack its
>   bytes. (checked using pahole)

You forgot to test your code and see what happens when you remove a
device :(