tty: n_gsm: fix encoding of command/response bit
n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516 The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to the newer 27.010 here. Chapter 5.2.1.2 describes the encoding of the C/R (command/response) bit. Table 1 shows that the actual encoding of the C/R bit is inverted if the associated frame is sent by the responder. The referenced commit fixed here further broke the internal meaning of this bit in the outgoing path by always setting the C/R bit regardless of the frame type. This patch fixes both by setting the C/R bit always consistently for command (1) and response (0) frames and inverting it later for the responder where necessary. The meaning of this bit in the debug output is being preserved and shows the bit as if it was encoded by the initiator. This reflects only the frame type rather than the encoded combination of communication side and frame type. Fixes: cc0f4212 ("tty: n_gsm: Modify CR,PF bit when config requester") Cc: stable@vger.kernel.org Signed-off-by:Daniel Starke <daniel.starke@siemens.com> Link: https://lore.kernel.org/r/20220218073123.2121-2-daniel.starke@siemens.com Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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