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i2c: Allow I2C devices to NAK start events

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Add a return value to the event handler.  Some I2C devices will
NAK if they have no data, so allow them to do this.  This required
the following changes:

Go through all the event handlers and change them to return int
and return 0.

Modify i2c_start_transfer to terminate the transaction on a NAK.

Modify smbus handing to not assert if a NAK occurs on a second
operation, and terminate the transaction and return -1 instead.

Add some information on semantics to I2CSlaveClass.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Corey Minyard 2017-01-09 11:40:20 +00:00 • committed by Peter Maydell
parent ffe22bf510
commit d307c28ca9
14 changed files with 79 additions and 26 deletions
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16
include/hw/i2c/i2c.h
View file

@ -32,14 +32,22 @@ typedef struct I2CSlaveClass
/* Callbacks provided by the device. */
int (*init)(I2CSlave *dev);
/* Master to slave. */
/* Master to slave. Returns non-zero for a NAK, 0 for success. */
int (*send)(I2CSlave *s, uint8_t data);
/* Slave to master. */
/*
* Slave to master. This cannot fail, the device should always
* return something here. Negative values probably result in 0xff
* and a possible log from the driver, and shouldn't be used.
*/
int (*recv)(I2CSlave *s);
/* Notify the slave of a bus state change. */
void (*event)(I2CSlave *s, enum i2c_event event);
/*
* Notify the slave of a bus state change. For start event,
* returns non-zero to NAK an operation. For other events the
* return code is not used and should be zero.
*/
int (*event)(I2CSlave *s, enum i2c_event event);
} I2CSlaveClass;
struct I2CSlave