On 2014-02-13 18:25, Hartley Sweeten wrote:
On Wednesday, February 12, 2014 8:29 PM, Chase Southwood wrote:In this if-else conditional statement, if (chan < 16), but (data[0] == INSN_CONFIG_DIO_QUERY), the function does not return early, but the else-branch does not get executed either. As a result, mask would be used uninitialized in the next line. What we want here is if (chan < 16) and (data[0] != INSN_CONFIG_DIO_QUERY), return an error, but in every other case, initialize mask and then proceed. Found by a static checker. Signed-off-by: Chase Southwood <chase.southwood@xxxxxxxxx> --- drivers/staging/comedi/drivers/addi_apci_3xxx.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/staging/comedi/drivers/addi_apci_3xxx.c b/drivers/staging/comedi/drivers/addi_apci_3xxx.c index ceadf8e..04c5153 100644 --- a/drivers/staging/comedi/drivers/addi_apci_3xxx.c +++ b/drivers/staging/comedi/drivers/addi_apci_3xxx.c @@ -688,13 +688,11 @@ static int apci3xxx_dio_insn_config(struct comedi_device *dev, * Port 1 (channels 8-15) are always outputs * Port 2 (channels 16-23) are programmable i/o */ - if (chan < 16) { - if (data[0] != INSN_CONFIG_DIO_QUERY) - return -EINVAL; - } else { - /* changing any channel in port 2 changes the entire port */ - mask = 0xff0000; - } + if ((chan < 16) && (data[0] != INSN_CONFIG_DIO_QUERY)) + return -EINVAL; + + /* changing any channel in port 2 changes the entire port */ + mask = 0xff0000; ret = comedi_dio_insn_config(dev, s, insn, data, mask); if (ret)The uninitialized mask when chan < 16 is an issue. But your patch is not quite correct. The original code was intending to limit the valid instructions for channels < 16 to only INSN_CONFIG_DIO_QUERY. These channels have fixed directions: 0-7 (port 0) are always inputs and 8-15 (port 1) are always outputs. Channels 16-23 (port 2) have programmable direction but changing any channel effects the entire port, that's what the 0xff0000 mask is for. Changing the mask to 0xff0000 for any chanspec will result in the INSN_CONFIG_DIO_QUERY instruction returning the direction of port 2 regardless of what the chanspec is. The "right" fix would be: 1) Default the mask to 0 so that comedi_dio_insn_config() will use a chan_mask based on the chanspec for the INSN_CONFIG_DIO_QUERY instruction. 2) Ignore all instructions except INSN_CONFIG_DIO_QUERY when the chan < 16. 3) Modify the mask for chan >= 16 when the instruction is not INSN_CONFIG_DIO_QUERY so that the INSN_CONFIG_DIO_{INPUT,OUTPUT} instructions update the entire port.
Agreed, but another question is why does comedi_dio_insn_config() in drivers.c need to look at the supplied mask at all for INSN_CONFIG_DIO_QUERY?
-- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=- _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
