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[0/1] media: dvb_frontend: add missing DSS switch cases

Message ID trinity-20af6998-4ae7-4160-91c0-b68583655a76-1641958333231@3c-app-gmx-bap21 (mailing list archive)
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Series media: dvb_frontend: add missing DSS switch cases | expand

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Robert Schlabbach Jan. 12, 2022, 3:32 a.m. UTC 
I was wondering why my multistandard scanning application, which tries
all delivery systems a frontend offers until it gets a signal, ended
up flooding the kernel log with messages like these:

DVB: adapter 0 frontend 0 frequency 1665500 out of range (850000000..2300000000)

Investigation brought about that this happened when the application
tried the SYS_DSS standard, which is a satellite delivery system as per
the documentation. However, it is missing from all but one switch
statement in dvb_frontend.c, causing the frequency requested to be
handled as being in Hz rather than kHz, and in consequence, dvb_frontend
to generate these log messages.

While I do not have any DSS signals to receive, nor expect to ever have
any, and from the omission in dvb_frontend.c presume noone else ever has,
I submit the following patch to put things right.

DSS is a pre-DVB-S standard with many similarities (such as modulation
being only QPSK), so the frontend drivers which support it handle it
mostly like DVB-S, meaning they expect to get the frequency in kHz.

For the rolloff factor, a popular search engine found a book which
states it is 0.20 in contrast DVB-S' 0.35. Code review of the existing
frontend drivers yielded they should have no issue with that, so I
added and used that value in dvb_frontend where applicable.

Signed-off-by: Robert Schlabbach <robert_s@gmx.net>