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media: dvb-core: frontend: make GET/SET safer
The implementation for FE_SET_PROPERTY/FE_GET_PROPERTY has a debug code that might be explored via spectre. Improve the logic in order to mitigate such risk. It should be noticed that, before this patch, the logic which implements FE_GET_PROPERTY doesn't check the length passed by the user, which might lead to expose some information. This is probably not exploitable, though, as the frontend drivers won't rely on the buffer length value set by userspace, but it helps to return a valid value back to userspace. The code was changed to only try to access an array based on userspace values only when DVB debug is turned on, helping to reduce the attack surface, as a speculation attack would work only if DVB dev_dbg() macros are enabled, which is usually enabled only on test Kernels or by the root user. As a side effect, a const array size can now be reduced by ~570 bytes, as it now needs to contain just the name of each DTV command. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Mauro Carvalho Chehab
parent
dba328bab4
commit
60f0618d15
@ -23,6 +23,7 @@
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#include <linux/poll.h>
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#include <linux/semaphore.h>
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#include <linux/module.h>
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#include <linux/nospec.h>
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#include <linux/list.h>
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#include <linux/freezer.h>
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#include <linux/jiffies.h>
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@ -1063,107 +1064,97 @@ static int dvb_frontend_clear_cache(struct dvb_frontend *fe)
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return 0;
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}
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#define _DTV_CMD(n, s, b) \
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[n] = { \
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.name = #n, \
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.cmd = n, \
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.set = s,\
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.buffer = b \
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}
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#define _DTV_CMD(n) \
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[n] = #n
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struct dtv_cmds_h {
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char *name; /* A display name for debugging purposes */
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__u32 cmd; /* A unique ID */
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/* Flags */
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__u32 set:1; /* Either a set or get property */
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__u32 buffer:1; /* Does this property use the buffer? */
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__u32 reserved:30; /* Align */
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};
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static struct dtv_cmds_h dtv_cmds[DTV_MAX_COMMAND + 1] = {
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_DTV_CMD(DTV_TUNE, 1, 0),
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_DTV_CMD(DTV_CLEAR, 1, 0),
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static char *dtv_cmds[DTV_MAX_COMMAND + 1] = {
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_DTV_CMD(DTV_TUNE),
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_DTV_CMD(DTV_CLEAR),
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/* Set */
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_DTV_CMD(DTV_FREQUENCY, 1, 0),
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_DTV_CMD(DTV_BANDWIDTH_HZ, 1, 0),
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_DTV_CMD(DTV_MODULATION, 1, 0),
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_DTV_CMD(DTV_INVERSION, 1, 0),
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_DTV_CMD(DTV_DISEQC_MASTER, 1, 1),
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_DTV_CMD(DTV_SYMBOL_RATE, 1, 0),
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_DTV_CMD(DTV_INNER_FEC, 1, 0),
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_DTV_CMD(DTV_VOLTAGE, 1, 0),
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_DTV_CMD(DTV_TONE, 1, 0),
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_DTV_CMD(DTV_PILOT, 1, 0),
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_DTV_CMD(DTV_ROLLOFF, 1, 0),
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_DTV_CMD(DTV_DELIVERY_SYSTEM, 1, 0),
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_DTV_CMD(DTV_HIERARCHY, 1, 0),
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_DTV_CMD(DTV_CODE_RATE_HP, 1, 0),
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_DTV_CMD(DTV_CODE_RATE_LP, 1, 0),
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_DTV_CMD(DTV_GUARD_INTERVAL, 1, 0),
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_DTV_CMD(DTV_TRANSMISSION_MODE, 1, 0),
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_DTV_CMD(DTV_INTERLEAVING, 1, 0),
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_DTV_CMD(DTV_FREQUENCY),
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_DTV_CMD(DTV_BANDWIDTH_HZ),
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_DTV_CMD(DTV_MODULATION),
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_DTV_CMD(DTV_INVERSION),
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_DTV_CMD(DTV_DISEQC_MASTER),
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_DTV_CMD(DTV_SYMBOL_RATE),
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_DTV_CMD(DTV_INNER_FEC),
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_DTV_CMD(DTV_VOLTAGE),
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_DTV_CMD(DTV_TONE),
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_DTV_CMD(DTV_PILOT),
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_DTV_CMD(DTV_ROLLOFF),
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_DTV_CMD(DTV_DELIVERY_SYSTEM),
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_DTV_CMD(DTV_HIERARCHY),
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_DTV_CMD(DTV_CODE_RATE_HP),
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_DTV_CMD(DTV_CODE_RATE_LP),
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_DTV_CMD(DTV_GUARD_INTERVAL),
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_DTV_CMD(DTV_TRANSMISSION_MODE),
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_DTV_CMD(DTV_INTERLEAVING),
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_DTV_CMD(DTV_ISDBT_PARTIAL_RECEPTION, 1, 0),
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_DTV_CMD(DTV_ISDBT_SOUND_BROADCASTING, 1, 0),
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_DTV_CMD(DTV_ISDBT_SB_SUBCHANNEL_ID, 1, 0),
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_DTV_CMD(DTV_ISDBT_SB_SEGMENT_IDX, 1, 0),
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_DTV_CMD(DTV_ISDBT_SB_SEGMENT_COUNT, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYER_ENABLED, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERA_FEC, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERA_MODULATION, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERA_SEGMENT_COUNT, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERA_TIME_INTERLEAVING, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERB_FEC, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERB_MODULATION, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERB_SEGMENT_COUNT, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERB_TIME_INTERLEAVING, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERC_FEC, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERC_MODULATION, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERC_SEGMENT_COUNT, 1, 0),
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_DTV_CMD(DTV_ISDBT_LAYERC_TIME_INTERLEAVING, 1, 0),
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_DTV_CMD(DTV_ISDBT_PARTIAL_RECEPTION),
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_DTV_CMD(DTV_ISDBT_SOUND_BROADCASTING),
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_DTV_CMD(DTV_ISDBT_SB_SUBCHANNEL_ID),
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_DTV_CMD(DTV_ISDBT_SB_SEGMENT_IDX),
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_DTV_CMD(DTV_ISDBT_SB_SEGMENT_COUNT),
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_DTV_CMD(DTV_ISDBT_LAYER_ENABLED),
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_DTV_CMD(DTV_ISDBT_LAYERA_FEC),
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_DTV_CMD(DTV_ISDBT_LAYERA_MODULATION),
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_DTV_CMD(DTV_ISDBT_LAYERA_SEGMENT_COUNT),
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_DTV_CMD(DTV_ISDBT_LAYERA_TIME_INTERLEAVING),
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_DTV_CMD(DTV_ISDBT_LAYERB_FEC),
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_DTV_CMD(DTV_ISDBT_LAYERB_MODULATION),
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_DTV_CMD(DTV_ISDBT_LAYERB_SEGMENT_COUNT),
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_DTV_CMD(DTV_ISDBT_LAYERB_TIME_INTERLEAVING),
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_DTV_CMD(DTV_ISDBT_LAYERC_FEC),
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_DTV_CMD(DTV_ISDBT_LAYERC_MODULATION),
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_DTV_CMD(DTV_ISDBT_LAYERC_SEGMENT_COUNT),
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_DTV_CMD(DTV_ISDBT_LAYERC_TIME_INTERLEAVING),
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_DTV_CMD(DTV_STREAM_ID, 1, 0),
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_DTV_CMD(DTV_DVBT2_PLP_ID_LEGACY, 1, 0),
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_DTV_CMD(DTV_SCRAMBLING_SEQUENCE_INDEX, 1, 0),
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_DTV_CMD(DTV_LNA, 1, 0),
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_DTV_CMD(DTV_STREAM_ID),
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_DTV_CMD(DTV_DVBT2_PLP_ID_LEGACY),
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_DTV_CMD(DTV_SCRAMBLING_SEQUENCE_INDEX),
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_DTV_CMD(DTV_LNA),
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/* Get */
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_DTV_CMD(DTV_DISEQC_SLAVE_REPLY, 0, 1),
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_DTV_CMD(DTV_API_VERSION, 0, 0),
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_DTV_CMD(DTV_DISEQC_SLAVE_REPLY),
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_DTV_CMD(DTV_API_VERSION),
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_DTV_CMD(DTV_ENUM_DELSYS, 0, 0),
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_DTV_CMD(DTV_ENUM_DELSYS),
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_DTV_CMD(DTV_ATSCMH_PARADE_ID, 1, 0),
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_DTV_CMD(DTV_ATSCMH_RS_FRAME_ENSEMBLE, 1, 0),
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_DTV_CMD(DTV_ATSCMH_PARADE_ID),
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_DTV_CMD(DTV_ATSCMH_RS_FRAME_ENSEMBLE),
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_DTV_CMD(DTV_ATSCMH_FIC_VER, 0, 0),
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_DTV_CMD(DTV_ATSCMH_NOG, 0, 0),
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_DTV_CMD(DTV_ATSCMH_TNOG, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SGN, 0, 0),
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_DTV_CMD(DTV_ATSCMH_PRC, 0, 0),
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_DTV_CMD(DTV_ATSCMH_RS_FRAME_MODE, 0, 0),
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_DTV_CMD(DTV_ATSCMH_RS_CODE_MODE_PRI, 0, 0),
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_DTV_CMD(DTV_ATSCMH_RS_CODE_MODE_SEC, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SCCC_BLOCK_MODE, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_A, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_B, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_C, 0, 0),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_D, 0, 0),
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_DTV_CMD(DTV_ATSCMH_FIC_VER),
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_DTV_CMD(DTV_ATSCMH_NOG),
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_DTV_CMD(DTV_ATSCMH_TNOG),
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_DTV_CMD(DTV_ATSCMH_SGN),
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_DTV_CMD(DTV_ATSCMH_PRC),
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_DTV_CMD(DTV_ATSCMH_RS_FRAME_MODE),
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_DTV_CMD(DTV_ATSCMH_RS_CODE_MODE_PRI),
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_DTV_CMD(DTV_ATSCMH_RS_CODE_MODE_SEC),
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_DTV_CMD(DTV_ATSCMH_SCCC_BLOCK_MODE),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_A),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_B),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_C),
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_DTV_CMD(DTV_ATSCMH_SCCC_CODE_MODE_D),
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/* Statistics API */
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_DTV_CMD(DTV_STAT_SIGNAL_STRENGTH, 0, 0),
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_DTV_CMD(DTV_STAT_CNR, 0, 0),
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_DTV_CMD(DTV_STAT_PRE_ERROR_BIT_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_PRE_TOTAL_BIT_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_POST_ERROR_BIT_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_POST_TOTAL_BIT_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_ERROR_BLOCK_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_TOTAL_BLOCK_COUNT, 0, 0),
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_DTV_CMD(DTV_STAT_SIGNAL_STRENGTH),
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_DTV_CMD(DTV_STAT_CNR),
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_DTV_CMD(DTV_STAT_PRE_ERROR_BIT_COUNT),
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_DTV_CMD(DTV_STAT_PRE_TOTAL_BIT_COUNT),
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_DTV_CMD(DTV_STAT_POST_ERROR_BIT_COUNT),
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_DTV_CMD(DTV_STAT_POST_TOTAL_BIT_COUNT),
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_DTV_CMD(DTV_STAT_ERROR_BLOCK_COUNT),
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_DTV_CMD(DTV_STAT_TOTAL_BLOCK_COUNT),
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};
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static char *dtv_cmd_name(u32 cmd)
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{
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cmd = array_index_nospec(cmd, DTV_MAX_COMMAND);
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return dtv_cmds[cmd];
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}
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/* Synchronise the legacy tuning parameters into the cache, so that demodulator
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* drivers can use a single set_frontend tuning function, regardless of whether
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* it's being used for the legacy or new API, reducing code and complexity.
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@ -1346,6 +1337,7 @@ static int dtv_property_process_get(struct dvb_frontend *fe,
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struct file *file)
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{
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int ncaps;
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unsigned int len = 1;
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switch (tvp->cmd) {
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case DTV_ENUM_DELSYS:
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@ -1355,6 +1347,7 @@ static int dtv_property_process_get(struct dvb_frontend *fe,
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ncaps++;
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}
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tvp->u.buffer.len = ncaps;
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len = ncaps;
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break;
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case DTV_FREQUENCY:
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tvp->u.data = c->frequency;
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@ -1532,27 +1525,51 @@ static int dtv_property_process_get(struct dvb_frontend *fe,
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/* Fill quality measures */
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case DTV_STAT_SIGNAL_STRENGTH:
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tvp->u.st = c->strength;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_CNR:
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tvp->u.st = c->cnr;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_PRE_ERROR_BIT_COUNT:
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tvp->u.st = c->pre_bit_error;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_PRE_TOTAL_BIT_COUNT:
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tvp->u.st = c->pre_bit_count;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_POST_ERROR_BIT_COUNT:
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tvp->u.st = c->post_bit_error;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_POST_TOTAL_BIT_COUNT:
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tvp->u.st = c->post_bit_count;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_ERROR_BLOCK_COUNT:
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tvp->u.st = c->block_error;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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case DTV_STAT_TOTAL_BLOCK_COUNT:
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tvp->u.st = c->block_count;
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if (tvp->u.buffer.len > MAX_DTV_STATS * sizeof(u32))
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tvp->u.buffer.len = MAX_DTV_STATS * sizeof(u32);
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len = tvp->u.buffer.len;
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break;
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default:
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dev_dbg(fe->dvb->device,
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@ -1561,18 +1578,13 @@ static int dtv_property_process_get(struct dvb_frontend *fe,
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return -EINVAL;
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}
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if (!dtv_cmds[tvp->cmd].buffer)
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dev_dbg(fe->dvb->device,
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"%s: GET cmd 0x%08x (%s) = 0x%08x\n",
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__func__, tvp->cmd, dtv_cmds[tvp->cmd].name,
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tvp->u.data);
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else
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dev_dbg(fe->dvb->device,
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"%s: GET cmd 0x%08x (%s) len %d: %*ph\n",
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__func__,
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tvp->cmd, dtv_cmds[tvp->cmd].name,
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tvp->u.buffer.len,
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tvp->u.buffer.len, tvp->u.buffer.data);
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if (len < 1)
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len = 1;
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dev_dbg(fe->dvb->device,
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"%s: GET cmd 0x%08x (%s) len %d: %*ph\n",
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__func__, tvp->cmd, dtv_cmd_name(tvp->cmd),
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tvp->u.buffer.len, tvp->u.buffer.len, tvp->u.buffer.data);
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return 0;
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}
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@ -1870,7 +1882,7 @@ static int dtv_property_process_set(struct dvb_frontend *fe,
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else
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dev_dbg(fe->dvb->device,
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"%s: SET cmd 0x%08x (%s) to 0x%08x\n",
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__func__, cmd, dtv_cmds[cmd].name, data);
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__func__, cmd, dtv_cmd_name(cmd), data);
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switch (cmd) {
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case DTV_CLEAR:
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/*
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