| Message ID | 1477332749-27098-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
Ping? This is a bugfix and a coverity warning fix so it would be nice if it could go into 2.8. thanks -- PMM On 24 October 2016 at 19:12, Peter Maydell <peter.maydell@linaro.org> wrote: > If the guest attempts to talk to a nonexistent device over i2c, > the i2c_start_transfer() function will return non-zero, indicating > that the bus is signalling a NACK. Similarly, if the i2c_send() > function returns nonzero then the target device returned a NACK. > Handle this possibility in the bitbang_i2c code, by returning > the state machine to the STOPPED state and returning the NACK > bit to the guest. > > This bit of missing functionality was spotted by Coverity > (it noticed that we weren't checking the return value from > i2c_start_transfer()). > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > Lightly tested using the musicpal board, which is the only one > using the bitbang_i2c code. If you make the board put the > Wolfson 8750 at the wrong I2C address then the guest will > retry the transaction a few times and give up, as expected. > Without this patch it will send a bunch of data out into > the void without realizing there's a problem. > --- > hw/i2c/bitbang_i2c.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/hw/i2c/bitbang_i2c.c b/hw/i2c/bitbang_i2c.c > index d3a2989..8be88ee 100644 > --- a/hw/i2c/bitbang_i2c.c > +++ b/hw/i2c/bitbang_i2c.c > @@ -130,14 +130,25 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level) > return bitbang_i2c_ret(i2c, 1); > > case WAITING_FOR_ACK: > + { > + int ret; > + > if (i2c->current_addr < 0) { > i2c->current_addr = i2c->buffer; > DPRINTF("Address 0x%02x\n", i2c->current_addr); > - i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, > - i2c->current_addr & 1); > + ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, > + i2c->current_addr & 1); > } else { > DPRINTF("Sent 0x%02x\n", i2c->buffer); > - i2c_send(i2c->bus, i2c->buffer); > + ret = i2c_send(i2c->bus, i2c->buffer); > + } > + if (ret) { > + /* NACK (either addressing a nonexistent device, or the > + * device we were sending to decided to NACK us). > + */ > + DPRINTF("Got NACK\n"); > + bitbang_i2c_enter_stop(i2c); > + return bitbang_i2c_ret(i2c, 1); > } > if (i2c->current_addr & 1) { > i2c->state = RECEIVING_BIT7; > @@ -145,7 +156,7 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level) > i2c->state = SENDING_BIT7; > } > return bitbang_i2c_ret(i2c, 0); > - > + } > case RECEIVING_BIT7: > i2c->buffer = i2c_recv(i2c->bus); > DPRINTF("RX byte 0x%02x\n", i2c->buffer); > -- > 2.7.4 > >
diff --git a/hw/i2c/bitbang_i2c.c b/hw/i2c/bitbang_i2c.c index d3a2989..8be88ee 100644 --- a/hw/i2c/bitbang_i2c.c +++ b/hw/i2c/bitbang_i2c.c @@ -130,14 +130,25 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level) return bitbang_i2c_ret(i2c, 1); case WAITING_FOR_ACK: + { + int ret; + if (i2c->current_addr < 0) { i2c->current_addr = i2c->buffer; DPRINTF("Address 0x%02x\n", i2c->current_addr); - i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, - i2c->current_addr & 1); + ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, + i2c->current_addr & 1); } else { DPRINTF("Sent 0x%02x\n", i2c->buffer); - i2c_send(i2c->bus, i2c->buffer); + ret = i2c_send(i2c->bus, i2c->buffer); + } + if (ret) { + /* NACK (either addressing a nonexistent device, or the + * device we were sending to decided to NACK us). + */ + DPRINTF("Got NACK\n"); + bitbang_i2c_enter_stop(i2c); + return bitbang_i2c_ret(i2c, 1); } if (i2c->current_addr & 1) { i2c->state = RECEIVING_BIT7; @@ -145,7 +156,7 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level) i2c->state = SENDING_BIT7; } return bitbang_i2c_ret(i2c, 0); - + } case RECEIVING_BIT7: i2c->buffer = i2c_recv(i2c->bus); DPRINTF("RX byte 0x%02x\n", i2c->buffer);
If the guest attempts to talk to a nonexistent device over i2c, the i2c_start_transfer() function will return non-zero, indicating that the bus is signalling a NACK. Similarly, if the i2c_send() function returns nonzero then the target device returned a NACK. Handle this possibility in the bitbang_i2c code, by returning the state machine to the STOPPED state and returning the NACK bit to the guest. This bit of missing functionality was spotted by Coverity (it noticed that we weren't checking the return value from i2c_start_transfer()). Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- Lightly tested using the musicpal board, which is the only one using the bitbang_i2c code. If you make the board put the Wolfson 8750 at the wrong I2C address then the guest will retry the transaction a few times and give up, as expected. Without this patch it will send a bunch of data out into the void without realizing there's a problem. --- hw/i2c/bitbang_i2c.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) -- 2.7.4