drivers: phy: Make NULL a valid phy reference

The common clock framework considers NULL a valid clock
reference. This makes handling optional clocks simple, in that if the
optional clock is not available, a NULL reference can be used in the
place of a real clock, simplifying the clock consumer.

Extend this concept to the phy consumer API. A NULL can be passed to
the release calls, the phy_init() and phy_exit() calls, and
phy_power_on() and phy_power_off() and a NOP is performed.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/phy.txt b/Documentation/phy.txt
index 0103e4b15b0..2e24b993e95 100644
--- a/Documentation/phy.txt
+++ b/Documentation/phy.txt
@@ -84,6 +84,12 @@ The only difference between the two APIs is that devm_phy_get associates the
 device with the PHY using devres on successful PHY get. On driver detach,
 release function is invoked on the the devres data and devres data is freed.
 
+It should be noted that NULL is a valid phy reference. All phy
+consumer calls on the NULL phy become NOPs. That is the release calls,
+the phy_init() and phy_exit() calls, and phy_power_on() and
+phy_power_off() calls are all NOP when applied to a NULL phy. The NULL
+phy is useful in devices for handling optional phy devices.
+
 5. Releasing a reference to the PHY
 
 When the controller no longer needs the PHY, it has to release the reference