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b7c25b11b6
Sandbox i2c works using emulation drivers which are currently children of
the i2c device:
rtc_0: rtc@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@chromium.org>
90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (c) 2014 Google, Inc
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*/
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#include <common.h>
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#include <dm.h>
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#include <i2c.h>
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#include <dm/device-internal.h>
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#include <dm/uclass-internal.h>
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/*
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* i2c emulation works using an 'emul' node at the bus level. Each device in
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* that node is in the UCLASS_I2C_EMUL uclass, and emulates one i2c device. A
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* pointer to the device it emulates is in the 'dev' property of the emul device
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* uclass platdata (struct i2c_emul_platdata), put there by i2c_emul_find().
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* When sandbox wants an emulator for a device, it calls i2c_emul_find() which
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* searches for the emulator with the correct address. To find the device for an
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* emulator, call i2c_emul_get_device().
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*
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* The 'emul' node is in the UCLASS_I2C_EMUL_PARENT uclass. We use a separate
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* uclass so avoid having strange devices on the I2C bus.
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*/
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/**
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* struct i2c_emul_uc_platdata - information about the emulator for this device
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*
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* This is used by devices in UCLASS_I2C_EMUL to record information about the
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* device being emulated. It is accessible with dev_get_uclass_platdata()
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*
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* @dev: Device being emulated
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*/
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struct i2c_emul_uc_platdata {
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struct udevice *dev;
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};
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struct udevice *i2c_emul_get_device(struct udevice *emul)
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{
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struct i2c_emul_uc_platdata *uc_plat = dev_get_uclass_platdata(emul);
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return uc_plat->dev;
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}
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int i2c_emul_find(struct udevice *dev, struct udevice **emulp)
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{
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struct i2c_emul_uc_platdata *uc_plat;
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struct udevice *emul;
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int ret;
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ret = uclass_find_device_by_phandle(UCLASS_I2C_EMUL, dev,
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"sandbox,emul", &emul);
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if (ret) {
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log_err("No emulators for device '%s'\n", dev->name);
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return ret;
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}
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uc_plat = dev_get_uclass_platdata(emul);
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uc_plat->dev = dev;
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*emulp = emul;
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return device_probe(emul);
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}
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UCLASS_DRIVER(i2c_emul) = {
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.id = UCLASS_I2C_EMUL,
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.name = "i2c_emul",
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.per_device_platdata_auto_alloc_size =
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sizeof(struct i2c_emul_uc_platdata),
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};
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/*
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* This uclass is a child of the i2c bus. Its platdata is not defined here so
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* is defined by its parent, UCLASS_I2C, which uses struct dm_i2c_chip. See
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* per_child_platdata_auto_alloc_size in UCLASS_DRIVER(i2c).
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*/
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UCLASS_DRIVER(i2c_emul_parent) = {
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.id = UCLASS_I2C_EMUL_PARENT,
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.name = "i2c_emul_parent",
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.post_bind = dm_scan_fdt_dev,
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};
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static const struct udevice_id i2c_emul_parent_ids[] = {
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{ .compatible = "sandbox,i2c-emul-parent" },
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{ }
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};
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U_BOOT_DRIVER(i2c_emul_parent_drv) = {
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.name = "i2c_emul_parent_drv",
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.id = UCLASS_I2C_EMUL_PARENT,
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.of_match = i2c_emul_parent_ids,
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};
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