linux-stable/drivers/i2c/i2c-boardinfo.c
Luis R. Rodriguez 5abe9b2684 i2c: remove __init from i2c_register_board_info()
As of next-20160607 with allyesconfig we get this linker failure:

  MODPOST vmlinux.o
WARNING: vmlinux.o(.text+0x21bc0d): Section mismatch in reference from
the function intel_scu_devices_create() to the function
.init.text:i2c_register_board_info()

This is caused by the fact that intel_scu_devices_create() calls
i2c_register_board_info() and intel_scu_devices_create() is not
annotated with __init. This typically involves manual code
inspection and if one is certain this is correct we would
just peg intel_scu_devices_create() with a __ref annotation.

In this case this would be wrong though as the
intel_scu_devices_create() call is exported, and used in
the ipc_probe() on drivers/platform/x86/intel_scu_ipc.c.
The issue is that even though builtin_pci_driver(ipc_driver)
is used this just exposes the probe routine, which can occur
at any point in time if this bus supports hotplug. A race
can happen between kernel_init_freeable() that calls the init
calls (in this case registeres the intel_scu_ipc.c driver, and
later free_initmem(), which would free the i2c_register_board_info().
If a probe happens later in boot i2c_register_board_info() would
not be present and we should get a page fault.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
[wsa: made function declaration a one-liner]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-06-19 14:13:50 +02:00

87 lines
2.8 KiB
C

/*
* i2c-boardinfo.c - collect pre-declarations of I2C devices
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/export.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include "i2c-core.h"
/* These symbols are exported ONLY FOR the i2c core.
* No other users will be supported.
*/
DECLARE_RWSEM(__i2c_board_lock);
EXPORT_SYMBOL_GPL(__i2c_board_lock);
LIST_HEAD(__i2c_board_list);
EXPORT_SYMBOL_GPL(__i2c_board_list);
int __i2c_first_dynamic_bus_num;
EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
/**
* i2c_register_board_info - statically declare I2C devices
* @busnum: identifies the bus to which these devices belong
* @info: vector of i2c device descriptors
* @len: how many descriptors in the vector; may be zero to reserve
* the specified bus number.
*
* Systems using the Linux I2C driver stack can declare tables of board info
* while they initialize. This should be done in board-specific init code
* near arch_initcall() time, or equivalent, before any I2C adapter driver is
* registered. For example, mainboard init code could define several devices,
* as could the init code for each daughtercard in a board stack.
*
* The I2C devices will be created later, after the adapter for the relevant
* bus has been registered. After that moment, standard driver model tools
* are used to bind "new style" I2C drivers to the devices. The bus number
* for any device declared using this routine is not available for dynamic
* allocation.
*
* The board info passed can safely be __initdata, but be careful of embedded
* pointers (for platform_data, functions, etc) since that won't be copied.
*/
int i2c_register_board_info(int busnum, struct i2c_board_info const *info, unsigned len)
{
int status;
down_write(&__i2c_board_lock);
/* dynamic bus numbers will be assigned after the last static one */
if (busnum >= __i2c_first_dynamic_bus_num)
__i2c_first_dynamic_bus_num = busnum + 1;
for (status = 0; len; len--, info++) {
struct i2c_devinfo *devinfo;
devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
if (!devinfo) {
pr_debug("i2c-core: can't register boardinfo!\n");
status = -ENOMEM;
break;
}
devinfo->busnum = busnum;
devinfo->board_info = *info;
list_add_tail(&devinfo->list, &__i2c_board_list);
}
up_write(&__i2c_board_lock);
return status;
}