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bae1d3a05a
Commitcea443a81c("i2c: Support i2c_transfer in atomic contexts") added in_atomic() to the I2C core. However, the use of in_atomic() outside of core kernel code is discouraged and was already[1] when this code was added in early 2008. The above commit was a preparation for commitb7a3670131("i2c-pxa: Add polling transfer"). Its commit message says explicitly it was added "for cases where I2C transactions have to occur at times interrup[t]s are disabled". So, the intention was 'disabled interrupts'. This matches the use cases for atomic I2C transfers I have seen so far: very late communication (mostly to a PMIC) to powerdown or reboot the system. For those cases, interrupts are disabled then. It doesn't seem that in_atomic() adds value. After a discussion with Peter Zijlstra[2], we came up with a better set of conditionals to match the use case. The I2C core will soon gain an extra callback into bus drivers especially for atomic transfers to make them more generic. The code deciding which transfer to use (atomic/non-atomic) should mimic the behaviour which locking to use (trylock/lock). This is why we add a helper for it. [1] https://lwn.net/Articles/274695/ [2] http://patchwork.ozlabs.org/patch/1067437/ Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Reviewed-by Andy Shevchenko <andriy.shevchenko@linux.intel.com> Tested-by: Stefan Lengfeld <contact@stefanchrist.eu> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/*
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* i2c-core.h - interfaces internal to the I2C framework
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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/rwsem.h>
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struct i2c_devinfo {
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struct list_head list;
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int busnum;
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struct i2c_board_info board_info;
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};
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/* board_lock protects board_list and first_dynamic_bus_num.
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* only i2c core components are allowed to use these symbols.
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*/
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extern struct rw_semaphore __i2c_board_lock;
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extern struct list_head __i2c_board_list;
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extern int __i2c_first_dynamic_bus_num;
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int i2c_check_7bit_addr_validity_strict(unsigned short addr);
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/*
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* We only allow atomic transfers for very late communication, e.g. to send
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* the powerdown command to a PMIC. Atomic transfers are a corner case and not
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* for generic use!
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*/
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static inline bool i2c_in_atomic_xfer_mode(void)
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{
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return system_state > SYSTEM_RUNNING && irqs_disabled();
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}
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#ifdef CONFIG_ACPI
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const struct acpi_device_id *
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i2c_acpi_match_device(const struct acpi_device_id *matches,
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struct i2c_client *client);
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void i2c_acpi_register_devices(struct i2c_adapter *adap);
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#else /* CONFIG_ACPI */
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static inline void i2c_acpi_register_devices(struct i2c_adapter *adap) { }
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static inline const struct acpi_device_id *
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i2c_acpi_match_device(const struct acpi_device_id *matches,
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struct i2c_client *client)
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{
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return NULL;
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}
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#endif /* CONFIG_ACPI */
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extern struct notifier_block i2c_acpi_notifier;
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#ifdef CONFIG_ACPI_I2C_OPREGION
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int i2c_acpi_install_space_handler(struct i2c_adapter *adapter);
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void i2c_acpi_remove_space_handler(struct i2c_adapter *adapter);
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#else /* CONFIG_ACPI_I2C_OPREGION */
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static inline int i2c_acpi_install_space_handler(struct i2c_adapter *adapter) { return 0; }
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static inline void i2c_acpi_remove_space_handler(struct i2c_adapter *adapter) { }
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#endif /* CONFIG_ACPI_I2C_OPREGION */
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#ifdef CONFIG_OF
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void of_i2c_register_devices(struct i2c_adapter *adap);
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#else
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static inline void of_i2c_register_devices(struct i2c_adapter *adap) { }
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#endif
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extern struct notifier_block i2c_of_notifier;
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