From d307c28ca9dba7a0677035c9244198b05164c873 Mon Sep 17 00:00:00 2001 From: Corey Minyard Date: Mon, 9 Jan 2017 11:40:20 +0000 Subject: i2c: Allow I2C devices to NAK start events 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 Reviewed-by: Peter Maydell Signed-off-by: Peter Maydell --- include/hw/i2c/i2c.h | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/hw/i2c/i2c.h b/include/hw/i2c/i2c.h index c4085aa..2ce611d 100644 --- a/include/hw/i2c/i2c.h +++ b/include/hw/i2c/i2c.h @@ -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 -- cgit v1.1