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dev/i2c_bus: Add declaration, implementation of i2c_dev_detect()

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This patch adds the I2C equivalent of an SMBus quick write to an I2C
device, which is used by some I2C drivers as a way to probe the
existence (or absence) of a certain device on the bus, based on
whether or not a 0-byte write to an I2C address is ACKed or NACKed.

i2c_dev_detect() is implemented using the existing i2c bus ops transfer()
function, so no further work is needed for existing controller drivers
to utilize this functionality.

Change-Id: I9b22bdc0343c846b235339f85d9f70b20f0f2bdd
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64537
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>
This commit is contained in:
Matt DeVillier
2022-05-19 19:03:07 -05:00
committed by Paul Fagerburg
parent 57097130d5
commit ee849ba625
2 changed files with 11 additions and 0 deletions
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6
src/device/i2c_bus.c
View File

@@ -6,6 +6,12 @@
#include <device/i2c_bus.h> #include <device/i2c_bus.h>
#include <commonlib/endian.h> #include <commonlib/endian.h>
bool i2c_dev_detect(struct device *dev, unsigned int addr)
{
struct i2c_msg seg = { .flags = 0, .slave = addr, .buf = NULL, .len = 0 };
return dev->ops->ops_i2c_bus->transfer(dev, &seg, 0) == 0;
}
struct bus *i2c_link(const struct device *const dev) struct bus *i2c_link(const struct device *const dev)
{ {
if (!dev || !dev->bus) if (!dev || !dev->bus)

5
src/include/device/i2c_bus.h
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@@ -13,6 +13,11 @@ struct i2c_bus_operations {
int (*transfer)(struct device *, const struct i2c_msg *, size_t count); int (*transfer)(struct device *, const struct i2c_msg *, size_t count);
}; };
/**
* Determine device presence at a given slave address.
*/
bool i2c_dev_detect(struct device *dev, unsigned int addr);
/* /*
* Returns the first upstream facing link whose bus implements either * Returns the first upstream facing link whose bus implements either
* `i2c_bus_operations` *or* `smbus_bus_operations`. * `i2c_bus_operations` *or* `smbus_bus_operations`.