modem-helpers: fix parsing of CREG/CGREG/CEREG responses

The format of CREG/CGREG/CEREG responses is not very precisely defined
in or strictly enforced by the 3GPP specifications. That leads to the
fact that some modems put leading zeros in integer type fields (e.g.
<n>, <stat>, <AcT>), and not all modems put double quotes around string
type fields (e.g. <lac>, <ci>) in those C*REG responses.

For example, 0001 can be a valid value for both <stat> and <lac>. The
original C*REG parsing code in ModemManager could potentially interpret
'+CREG: <stat>,<lac>,<ci>,<AcT>' as '+CREG: <n>,<stat>,<lac>,<ci>'. This
patch addresses this issue by refining the regular expressions returned
by mm_3gpp_creg_regex_get() with the following assumptions:

1. If a modem puts leading zeros in integer type fields, it puts double
   quotes around string type fields.
2. If a modem omits double quotes around string type fields, it does not
   put leading zeros in integer type fields.

0 files changed, 0 insertions, 0 deletions