[U-Boot] [PATCH v2 08/10] dm: sandbox: i2c: Add a new 'emulation parent' uclass

[sjg at google.com]

Sandbox i2c works using emulation drivers which are currently children of
the i2c device:

	rtc_0: rtc at 43 {
		reg = <0x43>;
		compatible = "sandbox-rtc";
		emul {
			compatible = "sandbox,i2c-rtc";
		};
	};

In this case the emulation device is attached to i2c bus on address 0x43
and provides the Real-Time-Clock (RTC) functionality.

However this is not ideal, since every device on an I2C bus has a child
device. This is only really the case for sandbox, but we want to avoid
special-case code for sandbox.

A better approach seems to be to add a separate node on the bus, an
'emulation parent'. This can be given a bogus address (such as 0xff) and
hides all the emulators away. Then we can use a phandle to point from the
device to the correct emualtor, and only on sandbox. The code to find an
emulator does not interfere with normal i2c operation.

Add a new UCLASS_I2C_EMUL_PARENT uclass which allows finding an emulator
given a bus, and finding a bus given an emulator. This will be used in a
follow-on patch.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

Changes in v2: None

 drivers/i2c/i2c-emul-uclass.c | 77 +++++++++++++++++++++++++++++++++++
 include/dm/uclass-id.h        |  1 +
 include/i2c.h                 | 21 ++++++++++
 3 files changed, 99 insertions(+)

Applied to u-boot-dm/master, thanks!