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i2c: Add asserts for second smbus i2c_start_transfer() 

Some SMBus operations restart the transfer to convert from
write to read mode without an intervening i2c_end_transfer().
The second call cannot fail, so the return code is unchecked,
but this causes Coverity to complain.  So add some asserts
and documentation about this.

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 2016-10-24 10:42:33 -05:00 committed by Peter Maydell
parent 19a6e31c9d
commit cc083d8a25
2 changed files with 15 additions and 4 deletions
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7
hw/i2c/core.c
View File

@ -88,7 +88,12 @@ int i2c_bus_busy(I2CBus *bus)
return !QLIST_EMPTY(&bus->current_devs);
}
/* Returns non-zero if the address is not valid. */
/*
* Returns non-zero if the address is not valid. If this is called
* again without an intervening i2c_end_transfer(), like in the SMBus
* case where the operation is switched from write to read, this
* function will not rescan the bus and thus cannot fail.
*/
/* TODO: Make this handle multiple masters. */
int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv)
{

12
hw/i2c/smbus.c
View File

@ -248,7 +248,9 @@ int smbus_read_byte(I2CBus *bus, uint8_t addr, uint8_t command)
return -1;
}
i2c_send(bus, command);
i2c_start_transfer(bus, addr, 1);
if (i2c_start_transfer(bus, addr, 1)) {
assert(0);
}
data = i2c_recv(bus);
i2c_nack(bus);
i2c_end_transfer(bus);
@ -273,7 +275,9 @@ int smbus_read_word(I2CBus *bus, uint8_t addr, uint8_t command)
return -1;
}
i2c_send(bus, command);
i2c_start_transfer(bus, addr, 1);
if (i2c_start_transfer(bus, addr, 1)) {
assert(0);
}
data = i2c_recv(bus);
data |= i2c_recv(bus) << 8;
i2c_nack(bus);
@ -302,7 +306,9 @@ int smbus_read_block(I2CBus *bus, uint8_t addr, uint8_t command, uint8_t *data)
return -1;
}
i2c_send(bus, command);
i2c_start_transfer(bus, addr, 1);
if (i2c_start_transfer(bus, addr, 1)) {
assert(0);
}
len = i2c_recv(bus);
if (len > 32) {
len = 0;