On Tuesday, February 18, 2014 4:36 AM, Ian Abbott wrote: > On 2014-02-17 21:27, H Hartley Sweeten wrote: >> The maximum chanlist that this hardware can handle is 16 (the number of >> input channels). >> >> Remove this incorrect data from the boardinfo and just initialize the >> subdevice 'len_chanlist' to subdevice 'n_chan'. > > The driver used to allow repeated channel segments in the channel list > (with a maximum segment length of 16), which would be far more > restricted by this patch. Is there any reason to restrict it? I don't think it's a restriction just a simplification. And it fixes the number of scans that occur when the chanlist repeats. The hardware can only handle a first channel (0-16) to last channel (0-16) scanlist. It will automatically restart the scanlist once the last channel has been sampled. For instance a first = 12 to last = 3 scanlist results in these channels being scanned: 12, 13, 14, 15, 0, 1, 2, 3, 12, 13, ... The cmd->scan_end_src can only be TRIG_COUNT in this driver. This trigger source argument is validated to be the cmd->chanlist_len, which in the example above should be 8. The cmd->stop_src can be TRIG_COUNT or TRIG_NONE. TRIG_NONE indicates that the scan should be continued until canceled. TRIG_COUNT indicates that the scan should happen cmd->stop_arg times. With the longer maximum chanlist value the user could pass a chanlist that had repeating first/last channels. This then needs to be sanity checked to make sure the first/last channels are identical with check_channel_list(). As a simple example, the old way a cmd with a chanlist like this could be passed: chanlist[0] -> channel 2 chanlist[1] -> channel 3 chanlist[2] -> channel 4 chanlist[0] -> channel 2 chanlist[1] -> channel 3 chanlist[2] -> channel 4 chanlist[0] -> channel 2 chanlist[1] -> channel 3 chanlist[2] -> channel 4 This is valid and indicates that channels 2-4 should be scanned 3 times. If the cmd->stop _src == TRIG_COUNT and cmd->stop_arg = 2 the full scan should then be 6 (3 repeats of the chanlist * 2) scans of channels 2-4. Unfortunately check_channel_list() does not return how many times the chanlist repeats so only 2 actual scans will occur. By changing the maximum chanlist to 16 we enforce the first/last channel scan and the cmd->stop_arg then scans the list the correct number of times. I still need to clean up the check_channel_list() functions to remove the now unnecessary check for the repeats. These functions should now just need to verify that the first/last channels are incremental. Regards, Hartley _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
