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drivers/power: Do not call gauge methods a driver did not implement. - #20506
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Whitespace only. Add a blank line after the declarations in the BATIOC_* cases, and indent two case labels like the others. The errors are older than the next commit, but checkpatch checks the whole file. Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
Every BATIOC_* case in the gauge upper half calls dev->ops->X() after checking only that the *argument* pointer is non-NULL. The operations themselves are optional -- max1704x.c implements four of the eight, and the in-tree fake gauge leaves chipid and operate NULL -- so asking a gauge for something it does not provide calls through a NULL pointer. On ARM that is not a null dereference but a branch to address 0, which has the Thumb bit clear: the core takes a usage fault with CFSR bit 17, INVSTATE, escalated to a hard fault. From userspace it looks like the program stopped mid-run for no reason, and on a board whose assert path delays before resetting it looks like a hang. Guard all eight. A missing method is now ENOTTY, which is what the default case already returns for an unrecognised command and what a caller can sensibly probe for. Tested on sim:nsh with the fake gauge and a local test app. Before the change, ioctl(BATIOC_CHIPID) kills the simulator with SIGSEGV. After the change, BATIOC_CHIPID and BATIOC_OPERATE return ENOTTY and BATIOC_VOLTAGE still returns the voltage. nucleo-f412zg:nsh with BATTERY_GAUGE, MAX1704X, BQ27426 and BATTERY_FAKE_GAUGE builds. Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
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xiaoxiang781216
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Oct 8, 2026
acassis
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Oct 8, 2026
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Summary
The battery gauge upper half calls
dev->ops->X()for everyBATIOC_*command, but it checks only the argument pointer. The operations are optional: max1704x implements 4 of 8, and the fake gauge leaveschipidandoperateNULL. A request for a missing method calls address 0. On ARM this is a hard fault (INVSTATE).This change checks each method pointer. A missing method now returns
-ENOTTY, the same value as an unknown command.The first commit fixes older nxstyle errors in
battery_gauge.c, because CI checks every file that a change touches. It changes whitespace only.Impact
Gauge drivers and their users only. Ioctls that crashed now return
ENOTTY. Implemented methods do not change.Testing
sim:nshwithBATTERY_GAUGEandBATTERY_FAKE_GAUGE. A local test app (not part of this PR) registers the fake gauge and sends ioctls to/dev/charge/fakegauge.Before:
After (errno 25 is
ENOTTY):nucleo-f412zg:nshwithBATTERY_GAUGE,MAX1704X,BQ27426andBATTERY_FAKE_GAUGEbuilds with arm-none-eabi-gcc 13.2.tools/checkpatch.sh -c -u -m -gpasses.