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/* i2c-core.c - a device driver for the iic-bus interface */ |
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/* ------------------------------------------------------------------------- */ |
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/* Copyright (C) 1995-99 Simon G. Vogl |
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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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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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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ |
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/* ------------------------------------------------------------------------- */ |
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/* With some changes from Kyösti Mälkki . |
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All SMBus-related things are written by Frodo Looijaard |
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SMBus 2.0 support by Mark Studebaker and |
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Jean Delvare */ |
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#include |
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#include |
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#include |
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#include |
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#include |
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/** |
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* i2c_transfer - execute a single or combined I2C message |
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* @adap: Handle to I2C bus |
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* @msgs: One or more messages to execute before STOP is issued to |
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* terminate the operation; each message begins with a START. |
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* @num: Number of messages to be executed. |
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* |
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* Returns negative errno, else the number of messages executed. |
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* |
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* Note that there is no requirement that each message be sent to |
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* the same slave address, although that is the most common model. |
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*/ |
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int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) |
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{ |
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unsigned long orig_jiffies; |
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int ret, try; |
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/* REVISIT the fault reporting model here is weak: |
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* |
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* - When we get an error after receiving N bytes from a slave, |
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* there is no way to report "N". |
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* |
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* - When we get a NAK after transmitting N bytes to a slave, |
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* there is no way to report "N" ... or to let the master |
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* continue executing the rest of this combined message, if |
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* that's the appropriate response. |
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* |
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* - When for example "num" is two and we successfully complete |
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* the first message but get an error part way through the |
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* second, it's unclear whether that should be reported as |
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* one (discarding status on the second message) or errno |
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* (discarding status on the first one). |
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*/ |
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if (adap->algo->master_xfer) { |
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#ifdef DEBUG |
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for (ret = 0; ret < num; ret++) { |
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dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, " |
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"len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD) |
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? 'R' : 'W', msgs[ret].addr, msgs[ret].len, |
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(msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : ""); |
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} |
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#endif |
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// if (in_atomic() || irqs_disabled()) { |
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// ret = mutex_trylock(&adap->bus_lock); |
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// if (!ret) |
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// /* I2C activity is ongoing. */ |
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// return -EAGAIN; |
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// } else { |
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// mutex_lock_nested(&adap->bus_lock, adap->level); |
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// } |
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/* Retry automatically on arbitration loss */ |
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// orig_jiffies = jiffies; |
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for (ret = 0, try = 0; try <= adap->retries; try++) { |
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ret = adap->algo->master_xfer(adap, msgs, num); |
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if (ret != -EAGAIN) |
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break; |
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// if (time_after(jiffies, orig_jiffies + adap->timeout)) |
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// break; |
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delay(1); |
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} |
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// mutex_unlock(&adap->bus_lock); |
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return ret; |
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} else { |
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// dev_dbg(&adap->dev, "I2C level transfers not supported\n"); |
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return -EOPNOTSUPP; |
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} |
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} |
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EXPORT_SYMBOL(i2c_transfer); |
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