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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>
Signed-off-by: Johan Hovold <johan@kernel.org>
48 lines
1.0 KiB
C
48 lines
1.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Generic serial GNSS receiver driver
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*
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* Copyright (C) 2018 Johan Hovold <johan@kernel.org>
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*/
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#ifndef _LINUX_GNSS_SERIAL_H
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#define _LINUX_GNSS_SERIAL_H
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#include <asm/termbits.h>
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#include <linux/pm.h>
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struct gnss_serial {
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struct serdev_device *serdev;
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struct gnss_device *gdev;
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speed_t speed;
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const struct gnss_serial_ops *ops;
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unsigned long drvdata[];
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};
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enum gnss_serial_pm_state {
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GNSS_SERIAL_OFF,
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GNSS_SERIAL_ACTIVE,
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GNSS_SERIAL_STANDBY,
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};
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struct gnss_serial_ops {
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int (*set_power)(struct gnss_serial *gserial,
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enum gnss_serial_pm_state state);
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};
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extern const struct dev_pm_ops gnss_serial_pm_ops;
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struct gnss_serial *gnss_serial_allocate(struct serdev_device *gserial,
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size_t data_size);
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void gnss_serial_free(struct gnss_serial *gserial);
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int gnss_serial_register(struct gnss_serial *gserial);
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void gnss_serial_deregister(struct gnss_serial *gserial);
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static inline void *gnss_serial_get_drvdata(struct gnss_serial *gserial)
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{
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return gserial->drvdata;
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}
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#endif /* _LINUX_GNSS_SERIAL_H */
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