include: device.h: Add named device attributes

Adds DEVICE_ATTR_[RW|RO|WO]_NAMED macros for adding attributes that
reuse the same sysfs name in a driver under separate subdirectories.

When dealing with some devices it can be useful to be able to reuse
the same name for similar attributes under a different subdirectory.
For example, a single logical HID endpoint may provide a configuration
interface for multiple physical devices. In such a case it is useful to
provide symmetrical attribute names under different subdirectories on
the configuration device. The Lenovo Legion Go is one such device,
providing configuration to a detachable left controller, detachable
right controller, the wireless transmission dongle, and the MCU. It is
therefore beneficial to treat each of these as individual devices in
the driver, providing a subdirectory for each physical device in the
sysfs. As some attributes are reused by each physical device, it
provides a much cleaner interface if the same driver can reuse the same
attribute name in sysfs while uniquely distinguishing the store/show
functions in the driver, rather than repeat string portions.

Example new WO attrs:
ATTRS{left_handle/reset}=="(not readable)"
ATTRS{right_handle/reset}=="(not readable)"
ATTRS{tx_dongle/reset}=="(not readable)"

vs old WO attrs in a subdir:
ATTRS{left_handle/left_handle_reset}=="(not readable)"
ATTRS{right_handle/right_handle_reset}=="(not readable)"
ATTRS{tx_dongle/tx_dongle_reset}=="(not readable)"

or old WO attrs with no subdir:
ATTRS{left_handle_reset}=="(not readable)"
ATTRS{right_handle_reset}=="(not readable)"
ATTRS{tx_dongle_reset}=="(not readable)"

While the third option is usable, it doesn't logically break up the
physical devices and creates a device directory with over 80 attributes
once all attrs are defined.

Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Derek J. Clark <derekjohn.clark@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

0 files changed, 0 insertions, 0 deletions