laforge has submitted this change. (
https://gerrit.osmocom.org/c/simtrace2/+/43124?usp=email )
Change subject: firmware: iso7816_3: fix F/D ratio for Di 8 and 9
......................................................................
firmware: iso7816_3: fix F/D ratio for Di 8 and 9
iso7816_3_compute_fd_ratio() multiplied F by D for every d_index >= 8,
presumably because the upper half of ISO 7816-3 Table 8 encodes 1/D.
But 7816-3 2006 and 1997 differ!
That assumption is only true for the range 1010..1111, which in the
2006 version is RFU. Indices 1000 and 1001 are Di = 12 and Di = 20,
see iso7816_3_di_table[].
So right now Fi=372/Di=12 -> 372 * 12 = 4464 instead of 372 / 12 =
31.
In the cemu value is rejected in emu_update_fidi()
and the old baud rate is silently kept.
In the sniffer update_fidi() programs US_FIDI as
4464 & 0x7ff = 368, which is garbage.
Use F/D for indices 1..9 and keep the legacy 1/D reading only for the RFU
range, where we cant really do anything useful anyway.
Change-Id: I44d6451d8b04aea2b0db7291b06a812afe84e52f
---
M firmware/libcommon/source/iso7816_fidi.c
1 file changed, 7 insertions(+), 3 deletions(-)
Approvals:
laforge: Looks good to me, but someone else must approve
Jenkins Builder: Verified
lynxis lazus: Looks good to me, approved
diff --git a/firmware/libcommon/source/iso7816_fidi.c
b/firmware/libcommon/source/iso7816_fidi.c
index 024663b..4e87dbd 100644
--- a/firmware/libcommon/source/iso7816_fidi.c
+++ b/firmware/libcommon/source/iso7816_fidi.c
@@ -48,9 +48,13 @@
if (d == 0)
return -EINVAL;
- /* See table 7 of ISO 7816-3: From 1000 on we divide by 1/d,
- * which equals a multiplication by d */
- if (d_index < 8)
+ /* DI defined in Table 8 of ISO/IEC 7816-3:2006
+ * has values 0001..1001 as div 1, 2, 4, 8, 16, 32, 64, 12, 20
+ * so indices 1..9 are all divisors and the ratio is F/D.
+ * But Indices 1010..1111 are RFU in the 2006 edition!
+ * 1997 used those for 1/2 .. 1/64, where dividing by 1/d equals
multiplying by d.
+ * Keep that legacy interpretation for the RFU range only. */
+ if (d_index < 10)
ret = f / d;
else
ret = f * d;
--
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Gerrit-MessageType: merged
Gerrit-Project: simtrace2
Gerrit-Branch: master
Gerrit-Change-Id: I44d6451d8b04aea2b0db7291b06a812afe84e52f
Gerrit-Change-Number: 43124
Gerrit-PatchSet: 1
Gerrit-Owner: Hoernchen <[email protected]>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <[email protected]>
Gerrit-Reviewer: lynxis lazus <[email protected]>
