5abe9b2684
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>
87 lines
2.8 KiB
C
87 lines
2.8 KiB
C
/*
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* i2c-boardinfo.c - collect pre-declarations of I2C devices
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/export.h>
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#include <linux/i2c.h>
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#include <linux/kernel.h>
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#include <linux/rwsem.h>
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#include <linux/slab.h>
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#include "i2c-core.h"
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/* These symbols are exported ONLY FOR the i2c core.
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* No other users will be supported.
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*/
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DECLARE_RWSEM(__i2c_board_lock);
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EXPORT_SYMBOL_GPL(__i2c_board_lock);
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LIST_HEAD(__i2c_board_list);
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EXPORT_SYMBOL_GPL(__i2c_board_list);
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int __i2c_first_dynamic_bus_num;
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EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
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/**
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* i2c_register_board_info - statically declare I2C devices
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* @busnum: identifies the bus to which these devices belong
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* @info: vector of i2c device descriptors
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* @len: how many descriptors in the vector; may be zero to reserve
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* the specified bus number.
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*
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* Systems using the Linux I2C driver stack can declare tables of board info
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* while they initialize. This should be done in board-specific init code
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* near arch_initcall() time, or equivalent, before any I2C adapter driver is
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* registered. For example, mainboard init code could define several devices,
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* as could the init code for each daughtercard in a board stack.
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*
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* The I2C devices will be created later, after the adapter for the relevant
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* bus has been registered. After that moment, standard driver model tools
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* are used to bind "new style" I2C drivers to the devices. The bus number
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* for any device declared using this routine is not available for dynamic
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* allocation.
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*
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* The board info passed can safely be __initdata, but be careful of embedded
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* pointers (for platform_data, functions, etc) since that won't be copied.
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*/
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int i2c_register_board_info(int busnum, struct i2c_board_info const *info, unsigned len)
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{
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int status;
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down_write(&__i2c_board_lock);
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/* dynamic bus numbers will be assigned after the last static one */
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if (busnum >= __i2c_first_dynamic_bus_num)
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__i2c_first_dynamic_bus_num = busnum + 1;
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for (status = 0; len; len--, info++) {
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struct i2c_devinfo *devinfo;
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devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
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if (!devinfo) {
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pr_debug("i2c-core: can't register boardinfo!\n");
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status = -ENOMEM;
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break;
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}
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devinfo->busnum = busnum;
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devinfo->board_info = *info;
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list_add_tail(&devinfo->list, &__i2c_board_list);
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}
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up_write(&__i2c_board_lock);
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return status;
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}
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