linux/drivers/hwspinlock/hwspinlock_internal.h
Gustavo A. R. Silva ef17f5193e hwspinlock: hwspinlock_internal.h: Replace zero-length array with flexible-array member
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]

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")

Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200319213839.GA10669@embeddedor.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
2020-03-25 22:30:46 -07:00

70 lines
2.0 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Hardware spinlocks internal header
*
* Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
*
* Contact: Ohad Ben-Cohen <ohad@wizery.com>
*/
#ifndef __HWSPINLOCK_HWSPINLOCK_H
#define __HWSPINLOCK_HWSPINLOCK_H
#include <linux/spinlock.h>
#include <linux/device.h>
struct hwspinlock_device;
/**
* struct hwspinlock_ops - platform-specific hwspinlock handlers
*
* @trylock: make a single attempt to take the lock. returns 0 on
* failure and true on success. may _not_ sleep.
* @unlock: release the lock. always succeed. may _not_ sleep.
* @relax: optional, platform-specific relax handler, called by hwspinlock
* core while spinning on a lock, between two successive
* invocations of @trylock. may _not_ sleep.
*/
struct hwspinlock_ops {
int (*trylock)(struct hwspinlock *lock);
void (*unlock)(struct hwspinlock *lock);
void (*relax)(struct hwspinlock *lock);
};
/**
* struct hwspinlock - this struct represents a single hwspinlock instance
* @bank: the hwspinlock_device structure which owns this lock
* @lock: initialized and used by hwspinlock core
* @priv: private data, owned by the underlying platform-specific hwspinlock drv
*/
struct hwspinlock {
struct hwspinlock_device *bank;
spinlock_t lock;
void *priv;
};
/**
* struct hwspinlock_device - a device which usually spans numerous hwspinlocks
* @dev: underlying device, will be used to invoke runtime PM api
* @ops: platform-specific hwspinlock handlers
* @base_id: id index of the first lock in this device
* @num_locks: number of locks in this device
* @lock: dynamically allocated array of 'struct hwspinlock'
*/
struct hwspinlock_device {
struct device *dev;
const struct hwspinlock_ops *ops;
int base_id;
int num_locks;
struct hwspinlock lock[];
};
static inline int hwlock_to_id(struct hwspinlock *hwlock)
{
int local_id = hwlock - &hwlock->bank->lock[0];
return hwlock->bank->base_id + local_id;
}
#endif /* __HWSPINLOCK_HWSPINLOCK_H */