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3931012141
llc_conn_ac_inc_npta_value() and llc_conn_ac_inc_tx_win_size()
clamp their counters to the maximum valid 7-bit value via
(u8) ~LLC_2_SEQ_NBR_MODULO. LLC_2_SEQ_NBR_MODULO is defined as
((u8) 128) in include/net/llc_pdu.h, but the (u8) cast does not
prevent integer promotion of the operand of ~: ~128 is computed
as int (0xffffff7f), and the surrounding (u8) cast truncates
back to 0x7f. The result is correct (127), but the implicit
truncation is flagged by sparse:
net/llc/llc_c_ac.c:1008:38: warning: cast truncates bits from
constant value (ffffff7f becomes 7f)
(and three more at lines 1009, 1099, 1100)
Replace the (u8) ~LLC_2_SEQ_NBR_MODULO expression with
LLC_2_SEQ_NBR_MODULO - 1, which evaluates to 127 directly and
silences sparse.
The same ~LLC_2_SEQ_NBR_MODULO pattern also appears in
include/net/llc_pdu.h:148 as part of PDU_GET_NEXT_Vr, but there
the result is immediately &-masked, so the int promotion is
harmless and sparse does not flag it; it is left alone.
This patch is the minimum diff to silence the warning. The
counter-clamp idiom itself could be modernized to
min_t(u8, ..., LLC_2_SEQ_NBR_MODULO - 1), but that is a
separate cleanup left for another patch.
No functional change.
Signed-off-by: Avinash Duduskar <avinash.duduskar@gmail.com>
Link: https://patch.msgid.link/20260513092253.3035961-1-avinash.duduskar@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>