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8695e0b1b9
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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*
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* i2c-mux.h - functions for the i2c-bus mux support
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*
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* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
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* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
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* Michael Lawnick <michael.lawnick.ext@nsn.com>
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*/
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#ifndef _LINUX_I2C_MUX_H
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#define _LINUX_I2C_MUX_H
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#ifdef __KERNEL__
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#include <linux/bitops.h>
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struct i2c_mux_core {
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struct i2c_adapter *parent;
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struct device *dev;
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unsigned int mux_locked:1;
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unsigned int arbitrator:1;
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unsigned int gate:1;
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void *priv;
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int (*select)(struct i2c_mux_core *, u32 chan_id);
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int (*deselect)(struct i2c_mux_core *, u32 chan_id);
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int num_adapters;
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int max_adapters;
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struct i2c_adapter *adapter[];
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};
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struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
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struct device *dev, int max_adapters,
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int sizeof_priv, u32 flags,
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int (*select)(struct i2c_mux_core *, u32),
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int (*deselect)(struct i2c_mux_core *, u32));
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/* flags for i2c_mux_alloc */
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#define I2C_MUX_LOCKED BIT(0)
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#define I2C_MUX_ARBITRATOR BIT(1)
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#define I2C_MUX_GATE BIT(2)
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static inline void *i2c_mux_priv(struct i2c_mux_core *muxc)
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{
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return muxc->priv;
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}
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struct i2c_adapter *i2c_root_adapter(struct device *dev);
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/*
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* Called to create an i2c bus on a multiplexed bus segment.
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* The chan_id parameter is passed to the select and deselect
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* callback functions to perform hardware-specific mux control.
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*/
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int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
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u32 force_nr, u32 chan_id,
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unsigned int class);
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void i2c_mux_del_adapters(struct i2c_mux_core *muxc);
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#endif /* __KERNEL__ */
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#endif /* _LINUX_I2C_MUX_H */
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