294 lines
6.8 KiB
C
294 lines
6.8 KiB
C
/*
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* I2C multiplexer
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*
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* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
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* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
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*
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* This module supports the PCA954x series of I2C multiplexer/switch chips
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* made by Philips Semiconductors.
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* This includes the:
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* PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
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* and PCA9548.
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*
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* These chips are all controlled via the I2C bus itself, and all have a
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* single 8-bit register. The upstream "parent" bus fans out to two,
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* four, or eight downstream busses or channels; which of these
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* are selected is determined by the chip type and register contents. A
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* mux can select only one sub-bus at a time; a switch can select any
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* combination simultaneously.
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*
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* Based on:
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* pca954x.c from Kumar Gala <galak@kernel.crashing.org>
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* Copyright (C) 2006
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*
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* Based on:
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* pca954x.c from Ken Harrenstien
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* Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
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*
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* Based on:
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* i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
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* and
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* pca9540.c from Jean Delvare <khali@linux-fr.org>.
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*
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/device.h>
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#include <linux/i2c.h>
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#include <linux/i2c-mux.h>
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#include <linux/i2c/pca954x.h>
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#define PCA954X_MAX_NCHANS 8
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enum pca_type {
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pca_9540,
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pca_9542,
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pca_9543,
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pca_9544,
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pca_9545,
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pca_9546,
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pca_9547,
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pca_9548,
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};
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struct pca954x {
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enum pca_type type;
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struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
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u8 last_chan; /* last register value */
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};
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struct chip_desc {
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u8 nchans;
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u8 enable; /* used for muxes only */
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enum muxtype {
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pca954x_ismux = 0,
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pca954x_isswi
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} muxtype;
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};
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/* Provide specs for the PCA954x types we know about */
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static const struct chip_desc chips[] = {
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[pca_9540] = {
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.nchans = 2,
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.enable = 0x4,
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.muxtype = pca954x_ismux,
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},
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[pca_9543] = {
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.nchans = 2,
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.muxtype = pca954x_isswi,
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},
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[pca_9544] = {
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.nchans = 4,
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.enable = 0x4,
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.muxtype = pca954x_ismux,
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},
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[pca_9545] = {
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.nchans = 4,
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.muxtype = pca954x_isswi,
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},
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[pca_9547] = {
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.nchans = 8,
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.enable = 0x8,
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.muxtype = pca954x_ismux,
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},
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[pca_9548] = {
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.nchans = 8,
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.muxtype = pca954x_isswi,
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},
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};
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static const struct i2c_device_id pca954x_id[] = {
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{ "pca9540", pca_9540 },
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{ "pca9542", pca_9540 },
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{ "pca9543", pca_9543 },
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{ "pca9544", pca_9544 },
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{ "pca9545", pca_9545 },
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{ "pca9546", pca_9545 },
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{ "pca9547", pca_9547 },
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{ "pca9548", pca_9548 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, pca954x_id);
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/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
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for this as they will try to lock adapter a second time */
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static int pca954x_reg_write(struct i2c_adapter *adap,
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struct i2c_client *client, u8 val)
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{
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int ret = -ENODEV;
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if (adap->algo->master_xfer) {
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struct i2c_msg msg;
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char buf[1];
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msg.addr = client->addr;
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msg.flags = 0;
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msg.len = 1;
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buf[0] = val;
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msg.buf = buf;
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ret = adap->algo->master_xfer(adap, &msg, 1);
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} else {
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union i2c_smbus_data data;
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ret = adap->algo->smbus_xfer(adap, client->addr,
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client->flags,
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I2C_SMBUS_WRITE,
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val, I2C_SMBUS_BYTE, &data);
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}
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return ret;
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}
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static int pca954x_select_chan(struct i2c_adapter *adap,
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void *client, u32 chan)
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{
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struct pca954x *data = i2c_get_clientdata(client);
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const struct chip_desc *chip = &chips[data->type];
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u8 regval;
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int ret = 0;
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/* we make switches look like muxes, not sure how to be smarter */
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if (chip->muxtype == pca954x_ismux)
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regval = chan | chip->enable;
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else
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regval = 1 << chan;
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/* Only select the channel if its different from the last channel */
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if (data->last_chan != regval) {
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ret = pca954x_reg_write(adap, client, regval);
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data->last_chan = regval;
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}
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return ret;
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}
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static int pca954x_deselect_mux(struct i2c_adapter *adap,
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void *client, u32 chan)
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{
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struct pca954x *data = i2c_get_clientdata(client);
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/* Deselect active channel */
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data->last_chan = 0;
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return pca954x_reg_write(adap, client, data->last_chan);
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}
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/*
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* I2C init/probing/exit functions
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*/
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static int pca954x_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
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struct pca954x_platform_data *pdata = client->dev.platform_data;
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int num, force, class;
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struct pca954x *data;
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int ret = -ENODEV;
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if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
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goto err;
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data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
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if (!data) {
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ret = -ENOMEM;
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goto err;
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}
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i2c_set_clientdata(client, data);
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/* Write the mux register at addr to verify
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* that the mux is in fact present. This also
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* initializes the mux to disconnected state.
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*/
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if (i2c_smbus_write_byte(client, 0) < 0) {
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dev_warn(&client->dev, "probe failed\n");
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goto exit_free;
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}
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data->type = id->driver_data;
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data->last_chan = 0; /* force the first selection */
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/* Now create an adapter for each channel */
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for (num = 0; num < chips[data->type].nchans; num++) {
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force = 0; /* dynamic adap number */
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class = 0; /* no class by default */
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if (pdata) {
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if (num < pdata->num_modes) {
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/* force static number */
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force = pdata->modes[num].adap_id;
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class = pdata->modes[num].class;
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} else
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/* discard unconfigured channels */
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break;
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}
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data->virt_adaps[num] =
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i2c_add_mux_adapter(adap, &client->dev, client,
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force, num, class, pca954x_select_chan,
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(pdata && pdata->modes[num].deselect_on_exit)
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? pca954x_deselect_mux : NULL);
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if (data->virt_adaps[num] == NULL) {
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ret = -ENODEV;
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dev_err(&client->dev,
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"failed to register multiplexed adapter"
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" %d as bus %d\n", num, force);
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goto virt_reg_failed;
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}
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}
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dev_info(&client->dev,
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"registered %d multiplexed busses for I2C %s %s\n",
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num, chips[data->type].muxtype == pca954x_ismux
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? "mux" : "switch", client->name);
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return 0;
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virt_reg_failed:
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for (num--; num >= 0; num--)
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i2c_del_mux_adapter(data->virt_adaps[num]);
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exit_free:
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kfree(data);
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err:
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return ret;
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}
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static int pca954x_remove(struct i2c_client *client)
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{
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struct pca954x *data = i2c_get_clientdata(client);
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const struct chip_desc *chip = &chips[data->type];
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int i, err;
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for (i = 0; i < chip->nchans; ++i)
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if (data->virt_adaps[i]) {
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err = i2c_del_mux_adapter(data->virt_adaps[i]);
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if (err)
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return err;
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data->virt_adaps[i] = NULL;
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}
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kfree(data);
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return 0;
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}
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static struct i2c_driver pca954x_driver = {
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.driver = {
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.name = "pca954x",
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.owner = THIS_MODULE,
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},
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.probe = pca954x_probe,
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.remove = pca954x_remove,
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.id_table = pca954x_id,
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};
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module_i2c_driver(pca954x_driver);
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MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
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MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
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MODULE_LICENSE("GPL v2");
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