109 lines
4.0 KiB
C
109 lines
4.0 KiB
C
/* 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 <kmalkki@cc.hut.fi>.
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All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
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SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
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Jean Delvare <khali@linux-fr.org> */
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#include <types.h>
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#include <list.h>
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#include <errno.h>
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#include <linux/i2c.h>
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#include <syscall.h>
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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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