Re: [PATCH v2 2/2] i2c: Multiplexed I2C bus multiplexer driver pca954x

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Hi Michael,

On Tue, 04 May 2010 14:48:21 +0200, Michael Lawnick wrote:
> Add multiplexed bus core support. I2C driver for PCA954x
> I2C multiplexer series.
> 
> Signed-off-by: Michael Lawnick <ml.lawnick-Mmb7MZpHnFY@public.gmane.org>


Review:
> 
> ---
> Based on kernel 2.6.33 +
> [PATCH] i2c-core: Use per-adapter userspace device lists
> by Jean Delware <20100424201914.08b3f008-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
> <http://article.gmane.org/gmane.linux.drivers.i2c/5994/>
> 
>  drivers/i2c/Kconfig         |    2 +
>  drivers/i2c/Makefile        |    2 +-
>  drivers/i2c/muxes/Kconfig   |   17 +++
>  drivers/i2c/muxes/Makefile  |    8 +
>  drivers/i2c/muxes/pca954x.c |  302 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/i2c/pca954x.h |   47 +++++++
>  6 files changed, 377 insertions(+), 1 deletions(-)
>  create mode 100755 drivers/i2c/muxes/Kconfig
>  create mode 100755 drivers/i2c/muxes/Makefile
>  create mode 100755 drivers/i2c/muxes/pca954x.c
>  create mode 100755 include/linux/i2c/pca954x.h

I don't really care, as I use quilt for my patches, but the above modes
are wrong: should be 100644.

> 
> diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> index 2cd6d78..21b0ac0 100755
> --- a/drivers/i2c/Kconfig
> +++ b/drivers/i2c/Kconfig
> @@ -44,6 +44,8 @@ config I2C_MUX
>  	  handle multiplexed I2C bus topologies, by presenting each
>  	  multiplexed segment as a I2C adapter.
>  
> +source drivers/i2c/muxes/Kconfig
> +
>  config I2C_CHARDEV
>  	tristate "I2C device interface"
>  	help
> diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
> index a488e8b..1769a16 100755
> --- a/drivers/i2c/Makefile
> +++ b/drivers/i2c/Makefile
> @@ -6,7 +6,7 @@ obj-$(CONFIG_I2C_BOARDINFO)	+= i2c-boardinfo.o
>  obj-$(CONFIG_I2C)		+= i2c-core.o
>  obj-$(CONFIG_I2C_CHARDEV)	+= i2c-dev.o
>  obj-$(CONFIG_I2C_MUX)		+= i2c-mux.o
> -obj-y				+= busses/ chips/ algos/
> +obj-y				+= busses/ chips/ muxes/ algos/
>  
>  ifeq ($(CONFIG_I2C_DEBUG_CORE),y)
>  EXTRA_CFLAGS += -DDEBUG
> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
> new file mode 100755
> index 0000000..ec22db0
> --- /dev/null
> +++ b/drivers/i2c/muxes/Kconfig
> @@ -0,0 +1,17 @@
> +#
> +# Multiplexer I2C chip drivers configuration
> +#
> +
> +menu "Multiplexer I2C Chip support"
> +	depends on I2C_MUX && EXPERIMENTAL

The dependency on EXPERIMENTAL is odd for a menu. I'd rather move it
down to individual drivers, so that we can them remove them later on a
case-by-case basis.

> +
> +config I2C_MUX_PCA954x
> +	tristate "Philips PCA954x I2C Mux/switches"
> +	help
> +	  If you say yes here you get support for the Philips PCA954x
> +	  I2C mux/switch devices.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called pca954x.
> +
> +endmenu
> diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
> new file mode 100755
> index 0000000..575c1ca
> --- /dev/null
> +++ b/drivers/i2c/muxes/Makefile
> @@ -0,0 +1,8 @@
> +#
> +# Makefile for multiplexer I2C chip drivers.
> +
> +obj-$(CONFIG_I2C_MUX_PCA954x)	+= pca954x.o
> +
> +ifeq ($(I2C_DEBUG_BUS),y)

I think you mean CONFIG_I2C_DEBUG_BUS here.

> +EXTRA_CFLAGS += -DDEBUG
> +endif
> diff --git a/drivers/i2c/muxes/pca954x.c b/drivers/i2c/muxes/pca954x.c
> new file mode 100755
> index 0000000..12b5eb7
> --- /dev/null
> +++ b/drivers/i2c/muxes/pca954x.c
> @@ -0,0 +1,302 @@
> +/*
> + * I2C multiplexer
> + *
> + * Copyright (c) 2008-2009 Rodolfo Giometti <giometti-k2GhghHVRtY@public.gmane.org>
> + * Copyright (c) 2008-2009 Eurotech S.p.A. <info-ymFC7zkAqBI1GQ1Ptb7lUw@public.gmane.org>
> + *
> + * This module supports the PCA954x series of I2C multiplexer/switch chips
> + * made by Philips Semiconductors.
> + * This includes the:
> + *	 PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
> + *	 and PCA9548.
> + *
> + * These chips are all controlled via the I2C bus itself, and all have a
> + * single 8-bit register. The upstream "parent" bus fans out to two,
> + * four, or eight downstream busses or channels; which of these
> + * are selected is determined by the chip type and register contents. A
> + * mux can select only one sub-bus at a time; a switch can select any
> + * combination simultaneously.
> + *
> + * Based on:
> + *	pca954x.c from Kumar Gala <galak-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
> + * Copyright (C) 2006
> + *
> + * Based on:
> + *	pca954x.c from Ken Harrenstien
> + * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
> + *
> + * Based on:
> + *	i2c-virtual_cb.c from Brian Kuschak <bkuschak-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>
> + * and
> + *	pca9540.c from Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>.
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/device.h>
> +#include <linux/i2c.h>
> +#include <linux/i2c-mux.h>
> +
> +#include <linux/i2c/pca954x.h>
> +
> +#define PCA954X_MAX_NCHANS 8
> +
> +enum pca_type {
> +	pca_9540,
> +	pca_9542,
> +	pca_9543,
> +	pca_9544,
> +	pca_9545,
> +	pca_9546,
> +	pca_9547,
> +	pca_9548,
> +};
> +
> +struct pca954x {
> +	enum	pca_type type;
> +	struct	i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
> +
> +	u8	last_chan;

This indentation doesn't make much sense.

> +};
> +
> +struct chip_desc {
> +	u8 nchans;
> +	u8 enable;	/* used for muxes only */
> +	enum muxtype {
> +		pca954x_ismux = 0,
> +		pca954x_isswi
> +	} muxtype;
> +};
> +
> +/* Provide specs for the PCA954x types we know about */
> +static const struct chip_desc chips[] = {
> +	[pca_9540] = {
> +		.nchans = 2,
> +		.enable = 0x4,
> +		.muxtype = pca954x_ismux,
> +	},
> +	[pca_9543] = {
> +		.nchans = 2,
> +		.muxtype = pca954x_isswi,
> +	},
> +	[pca_9544] = {
> +		.nchans = 4,
> +		.enable = 0x4,
> +		.muxtype = pca954x_ismux,
> +	},
> +	[pca_9545] = {
> +		.nchans = 4,
> +		.muxtype = pca954x_isswi,
> +	},
> +	[pca_9547] = {
> +		.nchans = 8,
> +		.enable = 0x8,
> +		.muxtype = pca954x_ismux,
> +	},
> +	[pca_9548] = {
> +		.nchans = 8,
> +		.muxtype = pca954x_isswi,
> +	},
> +};
> +
> +static const struct i2c_device_id pca954x_id[] = {
> +	{ "pca9540", pca_9540 },
> +	{ "pca9542", pca_9540 },
> +	{ "pca9543", pca_9543 },
> +	{ "pca9544", pca_9544 },
> +	{ "pca9545", pca_9545 },
> +	{ "pca9546", pca_9545 },
> +	{ "pca9547", pca_9547 },
> +	{ "pca9548", pca_9548 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, pca954x_id);
> +
> +/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
> +   for this as they will try to lock adapter a second time */
> +static int pca954x_reg_write(struct i2c_adapter *adap,
> +			     struct i2c_client *client, u8 val)
> +{
> +	int ret = -ENODEV;

Useless initialization.

> +
> +	if (adap->algo->master_xfer) {
> +		struct i2c_msg msg;
> +		char buf[1];
> +
> +		msg.addr = client->addr;
> +		msg.flags = I2C_SMBUS_WRITE;

That's not correct. You want to use 0 here (as writes are the default,
in the absence of I2C_M_RD).

> +		msg.len = 1;
> +		buf[0] = val;
> +		msg.buf = buf;
> +		ret = adap->algo->master_xfer(adap, &msg, 1);
> +	} else {
> +		union i2c_smbus_data data;
> +		ret = adap->algo->smbus_xfer(adap, client->addr,
> +					     client->flags,
> +					     I2C_SMBUS_WRITE,
> +					     val, I2C_SMBUS_BYTE, &data);
> +	}
> +
> +	return ret;
> +}
> +
> +static int pca954x_select_chan(struct i2c_adapter *adap,
> +			       void *client, u32 chan)
> +{
> +	struct pca954x *data = i2c_get_clientdata(client);
> +	const struct chip_desc *chip = &chips[data->type];
> +	u8 regval;
> +	int ret = 0;
> +
> +	/* we make switches look like muxes, not sure how to be smarter */
> +	if (chip->muxtype == pca954x_ismux)
> +		regval = chan | chip->enable;
> +	else
> +		regval = 1 << chan;
> +
> +	/* Only select the channel if its different from the last channel */
> +	if (data->last_chan != chan) {
> +		ret = pca954x_reg_write(adap, client, regval);
> +		data->last_chan = chan;
> +	}
> +
> +	return ret;
> +}
> +
> +static int pca954x_deselect_mux(struct i2c_adapter *adap,
> +				void *client, u32 chan)
> +{
> +	struct pca954x *data = i2c_get_clientdata(client);
> +
> +	/* Deselect active channel */
> +	data->last_chan = 0;
> +	return pca954x_reg_write(adap, client, data->last_chan);
> +}
> +
> +/*
> + * I2C init/probing/exit functions
> + */
> +static int __devinit pca954x_probe(struct i2c_client *client,
> +				   const struct i2c_device_id *id)
> +{
> +	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
> +	struct pca954x_platform_data *pdata = client->dev.platform_data;
> +	int num, force;
> +	struct pca954x *data;
> +	int ret = -ENODEV;
> +
> +	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
> +		goto err;
> +
> +	data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
> +	if (!data) {
> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	i2c_set_clientdata(client, data);
> +
> +	/* Read the mux register at addr to verify
> +	 * that the mux is in fact present.
> +	 */
> +	if (i2c_smbus_read_byte(client) < 0) {
> +		dev_warn(&client->dev, "probe failed\n");
> +		goto exit_free;
> +	}
> +
> +	data->type = id->driver_data;
> +	data->last_chan = 0;		   /* force the first selection */
> +
> +	/* Now create an adapter for each channel */
> +	for (num = 0; num < chips[data->type].nchans; num++) {
> +		force = 0;			  /* dynamic adap number */
> +		if (pdata) {
> +			if (num < pdata->num_modes)
> +				/* force static number */
> +				force = pdata->modes[num].adap_id;
> +			else
> +				/* discard unconfigured channels */
> +				break;
> +		}
> +
> +		data->virt_adaps[num] =
> +			i2c_add_mux_adapter(adap, client,
> +				force, num, &pca954x_select_chan,
> +				(pdata && pdata->modes[num].deselect_on_exit)
> +					? &pca954x_deselect_mux : NULL);

Functions are already addresses, the leading & isn't needed.

> +
> +		if (data->virt_adaps[num] == NULL) {
> +			ret = -ENODEV;
> +			printk(KERN_ERR

Please use dev_err().

> +				"%s %s: failed to register multiplexed adapter"
> +				" %d at bus %d\n", __FILE__, __func__, num,

I think you mean "as bus", not "at bus".

> +				force);
> +			goto virt_reg_failed;
> +		}
> +	}
> +
> +	dev_info(&client->dev,
> +		 "registered %d multiplexed busses for I2C %s %s\n",
> +		 num, chips[data->type].muxtype == pca954x_ismux
> +				? "mux" : "switch", client->name);
> +
> +	return 0;
> +
> +virt_reg_failed:
> +	for (num--; num >= 0; num--)
> +		i2c_del_mux_adapter(data->virt_adaps[num]);
> +exit_free:
> +	kfree(data);
> +err:
> +	return ret;
> +}
> +
> +static int __devexit pca954x_remove(struct i2c_client *client)
> +{
> +	struct pca954x *data = i2c_get_clientdata(client);
> +	const struct chip_desc *chip = &chips[data->type];
> +	int i, err;
> +
> +	for (i = 0; i < chip->nchans; ++i)
> +		if (data->virt_adaps[i]) {
> +			err = i2c_del_mux_adapter(data->virt_adaps[i]);
> +			if (err)
> +				return err;
> +			data->virt_adaps[i] = NULL;
> +		}
> +
> +	kfree(data);
> +	return 0;
> +}
> +
> +static struct i2c_driver pca954x_driver = {
> +	.driver		= {
> +		.name	= "pca954x",
> +		.owner	= THIS_MODULE,
> +	},
> +	.probe		= pca954x_probe,
> +	.remove		= __devexit_p(pca954x_remove),
> +	.id_table	= pca954x_id,
> +};
> +
> +static int __init pca954x_init(void)
> +{
> +	return i2c_add_driver(&pca954x_driver);
> +}
> +
> +static void __exit pca954x_exit(void)
> +{
> +	i2c_del_driver(&pca954x_driver);
> +}
> +
> +module_init(pca954x_init);
> +module_exit(pca954x_exit);
> +
> +MODULE_AUTHOR("Rodolfo Giometti <giometti-k2GhghHVRtY@public.gmane.org>");
> +MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/i2c/pca954x.h b/include/linux/i2c/pca954x.h
> new file mode 100755
> index 0000000..8032269
> --- /dev/null
> +++ b/include/linux/i2c/pca954x.h
> @@ -0,0 +1,47 @@
> +/*
> + *
> + * pca954x.h - I2C multiplexer/switch support
> + *
> + * Copyright (c) 2008-2009 Rodolfo Giometti <giometti-k2GhghHVRtY@public.gmane.org>
> + * Copyright (c) 2008-2009 Eurotech S.p.A. <info-ymFC7zkAqBI1GQ1Ptb7lUw@public.gmane.org>
> + * Michael Lawnick <michael.lawnick.ext-OYasijW0DpE@public.gmane.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +
> +#ifndef _I2C_PCA954X_H

Should be prefixed with _LINUX to avoid any confusion.

> +#define _I2C_PCA954X_H
> +
> +/* Platform data for the PCA954x I2C multiplexers */
> +
> +/* Per channel initialisation data:
> + * @adap_id: bus number for the adapter. 0 = don't care
> + * @deselect_on_exit: set this entry to 1, if your H/W needs deselection
> + *                    of this channel after transaction.
> + *
> + */
> +struct pca954x_platform_mode {
> +	int		adap_id;
> +	unsigned int	deselect_on_exit:1;
> +};
> +
> +/* Per mux/switch data, used with i2c_register_board_info */
> +struct pca954x_platform_data {
> +    struct pca954x_platform_mode *modes;
> +    int num_modes;

Please use tabs for indentation.

> +};
> +
> +#endif /*_I2C_PCA954X_H*/

Missing spaces.

I've fixed all these small issues myself; no need to resend. Thanks (to
you and Rodolfo as well) for your contribution!

-- 
Jean Delvare