Hi,

Please, find attached two patches related with the Comedi layer.

Each patch is a proposal to change the way the ranges tables are managed
within the subdevice structure. 

As you may know, the range structure allows the translation of freshly
acquired logical values into real values (thanks to the unit, the
minimal and the maximal value)

An acquisition subdevice can work with various ranges. That is why
some tab field is necessary to hold them all in the subdevice
descriptor structure. However, what I do not understand is why are
there two fields to handle them (and we cannot use both at the same
time).

Currently, according to the ranges' type: 
- either same ranges for all channels
- or a specific ranges table per channel,
we have to use the field range_table or the field range_table_list.

The range management could be made easier or at least more generic:
- the first proposal introduces a container structure. Thanks to its
  first field, we could define the range's type for a specific
  subdevice; and the second field is devoted to store comedi_lrange
  pointers. Some inline helper functions were added so as to manage
  the range without having to get through the structures.
- the second patch is the closest one from the original API. An internal
  structure is added (comedi_trange_struct) so as to handle per channel
  ranges tables. The internal range management code just has to detect
  which structure type is hidden behind the subdevice field range_table.

These patches are neither that clean nor perfect, they are just some
ideas I would like to share. By the way, these patches modify only the
core files (kcomedilib and the drivers have been left unchanged).

Best regards.

Alexis.