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Date: Thu, 4 Nov 2010 10:02:54 -0700
From: Guenter Roeck <guenter.roeck@...csson.com>
To: Ben Dooks <ben-i2c@...ff.org>
CC: Jean Delvare <khali@...ux-fr.org>, Ben Dooks <ben-linux@...ff.org>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/PATCH] i2c/busses: Add support for Diolan U2C-12 USB/I2C
adapter
Hi Ben,
wow, this is creating way more interest than I thought...
On Thu, 2010-11-04 at 08:47 -0400, Ben Dooks wrote:
> On Wed, Nov 03, 2010 at 05:26:29PM -0700, Guenter Roeck wrote:
> > Signed-off-by: Guenter Roeck <guenter.roeck@...csson.com>
> > ---
> > This is an usb-i2c adapter I am using to connect to i2c evaluation and test
> > boards. Not sure if it is worth adding it into the kernel. If yes, I'll be
> > happy to add myself as maintainer.
> >
> > drivers/i2c/busses/Kconfig | 10 +
> > drivers/i2c/busses/Makefile | 1 +
> > drivers/i2c/busses/i2c-diolan-u2c.c | 455 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 466 insertions(+), 0 deletions(-)
> > create mode 100644 drivers/i2c/busses/i2c-diolan-u2c.c
> >
> > diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> > index 3a6321c..d73be36 100644
> > --- a/drivers/i2c/busses/Kconfig
> > +++ b/drivers/i2c/busses/Kconfig
> > @@ -640,6 +640,16 @@ config I2C_XILINX
> >
> > comment "External I2C/SMBus adapter drivers"
> >
> > +config I2C_DIOLAN_U2C
> > + tristate "Diolan U2C-12 USB adapter"
> > + depends on USB
> > + help
> > + If you say yes to this option, support will be included for Diolan
> > + U2C-12, a USB to I2C interface.
> > +
> > + This driver can also be built as a module. If so, the module
> > + will be called i2c-diolan-u2c.
> > +
> > config I2C_PARPORT
> > tristate "Parallel port adapter"
> > depends on PARPORT
> > diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> > index 84cb16a..46315db 100644
> > --- a/drivers/i2c/busses/Makefile
> > +++ b/drivers/i2c/busses/Makefile
> > @@ -63,6 +63,7 @@ obj-$(CONFIG_I2C_OCTEON) += i2c-octeon.o
> > obj-$(CONFIG_I2C_XILINX) += i2c-xiic.o
> >
> > # External I2C/SMBus adapter drivers
> > +obj-$(CONFIG_I2C_DIOLAN_U2C) += i2c-diolan-u2c.o
> > obj-$(CONFIG_I2C_PARPORT) += i2c-parport.o
> > obj-$(CONFIG_I2C_PARPORT_LIGHT) += i2c-parport-light.o
> > obj-$(CONFIG_I2C_TAOS_EVM) += i2c-taos-evm.o
> > diff --git a/drivers/i2c/busses/i2c-diolan-u2c.c b/drivers/i2c/busses/i2c-diolan-u2c.c
> > new file mode 100644
> > index 0000000..5f4fb74
> > --- /dev/null
> > +++ b/drivers/i2c/busses/i2c-diolan-u2c.c
> > @@ -0,0 +1,455 @@
> > +/*
> > + * driver for the Diolan u2c-12 usb adapter
> > + *
> > + * Copyright (c) 2010 Ericsson AB
> > + *
> > + * Derived from:
> > + * i2c-tiny-usb.c
> > + * Copyright (C) 2006-2007 Till Harbaum (Till@...baum.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, version 2.
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/errno.h>
> > +#include <linux/module.h>
> > +#include <linux/types.h>
> > +#include <linux/slab.h>
> > +#include <linux/usb.h>
> > +#include <linux/i2c.h>
> > +
> > +#define USB_VENDOR_ID_DIOLAN 0x0abf
> > +#define USB_DEVICE_ID_DIOLAN_U2C 0x3370
> > +
> > +#define DIOLAN_OUT_EP 0x02
> > +#define DIOLAN_IN_EP 0x84
> > +
> > +/* commands via USB, must match command ids in the firmware */
> > +#define CMD_I2C_READ 0x01
> > +#define CMD_I2C_WRITE 0x02
> > +#define CMD_I2C_SCAN 0x03 /* Returns list of detected devices */
> > +#define CMD_I2C_RELEASE_SDA 0x04
> > +#define CMD_I2C_RELEASE_SCL 0x05
> > +#define CMD_I2C_DROP_SDA 0x06
> > +#define CMD_I2C_DROP_SCL 0x07
> > +#define CMD_I2C_READ_SDA 0x08
> > +#define CMD_I2C_READ_SCL 0x09
> > +#define CMD_GET_FW_VERSION 0x0a
> > +#define CMD_GET_SERIAL 0x0b
> > +#define CMD_I2C_START 0x0c
> > +#define CMD_I2C_STOP 0x0d
> > +#define CMD_I2C_REPEATED_START 0x0e
> > +#define CMD_I2C_PUT_BYTE 0x0f
> > +#define CMD_I2C_GET_BYTE 0x10
> > +#define CMD_I2C_PUT_ACK 0x11
> > +#define CMD_I2C_GET_ACK 0x12
> > +#define CMD_I2C_PUT_BYTE_ACK 0x13
> > +#define CMD_I2C_GET_BYTE_ACK 0x14
> > +#define CMD_I2C_SET_SPEED 0x1b
> > +#define CMD_I2C_GET_SPEED 0x1c
> > +#define CMD_SET_CLOCK_SYNCH 0x24
> > +#define CMD_GET_CLOCK_SYNCH 0x25
> > +#define CMD_SET_CLOCK_SYNCH_TO 0x26
> > +#define CMD_GET_CLOCK_SYNCH_TO 0x27
> > +
> > +#define RESP_OK 0x00
> > +#define RESP_FAILED 0x01
> > +#define RESP_BAD_MEMADDR 0x04
> > +#define RESP_DATA_ERR 0x05
> > +#define RESP_NOT_IMPLEMENTED 0x06
> > +#define RESP_NACK 0x07
> > +
> > +#define U2C_I2C_FREQ_FAST 0 /* 400 kHz */
> > +#define U2C_I2C_FREQ_STD 1 /* 100 kHz */
> > +#define U2C_I2C_FREQ_83KHZ 2
> > +#define U2C_I2C_FREQ_71KHZ 3
> > +#define U2C_I2C_FREQ_62KHZ 4
> > +#define U2C_I2C_FREQ_50KHZ 6
> > +#define U2C_I2C_FREQ_25KHZ 16
> > +#define U2C_I2C_FREQ_10KHZ 46
> > +#define U2C_I2C_FREQ_5KHZ 96
> > +#define U2C_I2C_FREQ_2KHZ 242
> > +
> > +#define DIOLAN_USB_TIMEOUT 100
> > +
> > +/* Structure to hold all of our device specific stuff */
> > +struct i2c_diolan_u2c {
> > + struct usb_device *usb_dev; /* the usb device for this device */
> > + struct usb_interface *interface;/* the interface for this device */
> > + struct i2c_adapter adapter; /* i2c related things */
> > +};
> > +
> > +/* usb layer */
> > +
> > +static int diolan_usb_transfer(struct i2c_adapter *adapter, u8 * obuffer,
> > + int olen, u8 *ibuffer, int ilen)
> > +{
> > + struct i2c_diolan_u2c *dev = adapter->algo_data;
> > + int ret = 0;
> > + int actual;
> > + unsigned char inbuffer[257];
> > +
> > + if (olen) {
> > + ret = usb_bulk_msg(dev->usb_dev,
> > + usb_sndbulkpipe(dev->usb_dev, DIOLAN_OUT_EP),
> > + obuffer, olen, &actual, DIOLAN_USB_TIMEOUT);
> > + }
> > + if (!ret) {
> > + ret = usb_bulk_msg(dev->usb_dev,
> > + usb_rcvbulkpipe(dev->usb_dev, DIOLAN_IN_EP),
> > + inbuffer, sizeof(inbuffer), &actual,
> > + DIOLAN_USB_TIMEOUT);
> > + if (ret == 0 && actual > 0) {
> > + ret = min(actual, ilen);
> > + switch (inbuffer[actual - 1]) {
> > + case RESP_NACK:
> > + ret = -EINVAL;
> > + goto abort;
> > + case RESP_OK:
> > + break;
> > + default:
> > + ret = -EIO;
> > + goto abort;
> > + }
> > + if (ret)
> > + memcpy(ibuffer, inbuffer, ret);
> > + }
> > + }
> > +abort:
> > + return ret;
> > +}
> > +
> > +/*
> > + * Flush input queue.
> > + * If we don't do this at startup and the controller has queued up
> > + * messages which were not retrieved, it will stop responding
> > + * at some point.
> > + */
> > +static void diolan_flush_input(struct usb_device *dev)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < 10; i++) {
> > + int actual = 0;
> > + int ret;
> > + u8 inbuffer[257];
> > +
> > + ret = usb_bulk_msg(dev, usb_rcvbulkpipe(dev, DIOLAN_IN_EP),
> > + inbuffer, sizeof(inbuffer), &actual,
> > + DIOLAN_USB_TIMEOUT);
> > + if (ret < 0 || actual == 0)
> > + break;
> > + }
> > +}
> > +
> > +static int diolan_i2c_start(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[1];
> > +
> > + buffer[0] = CMD_I2C_START;
> > +
> > + return diolan_usb_transfer(adapter, buffer, 1, buffer, 1);
> > +}
> > +
> > +static int diolan_i2c_repeated_start(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[1];
>
> note, transfers to/from stack memory are not advised, esp. if this
> involves the hardware dma-mapping the stack. Please move the buffer
> to your private data.
>
Thanks for the heads-up. I was not aware that there is a potential
problem.
> > + buffer[0] = CMD_I2C_REPEATED_START;
> > +
> > + return diolan_usb_transfer(adapter, buffer, 1, buffer, 1);
> > +}
>
> why not doing something like
>
> diolan_usb_cmd1(struct i2c_adapter *adapter, u8 command)
> {
> struct i2c_diolan_u2c *dev = adapter->algo_data;
>
> dev->buffer[0] = command;
>
> return diolan_usb_treansfer(adapter, dev->buffer, 1, dev->buffer, 1);
> }
>
> then a lot of these little transfer functions could be turned into much
> smaller ones.
>
> ie:
>
> static int diolan_i2c_stop(struct i2c_adapter *adapter)
> {
> return diolan_usb_cmd1(adapter, CMD_I2C_STOP);
> }
>
Good idea. I'll do that.
> > +static int diolan_i2c_stop(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[1];
> > +
> > + buffer[0] = CMD_I2C_STOP;
> > +
> > + return diolan_usb_transfer(adapter, buffer, 1, buffer, 1);
> > +}
> > +
> > +static int diolan_i2c_get_byte_ack(struct i2c_adapter *adapter, bool ack,
> > + u8 *byte)
> > +{
> > + u8 buffer[2];
> > + int rv;
> > +
> > + buffer[0] = CMD_I2C_GET_BYTE_ACK;
> > + buffer[1] = ack;
> > +
> > + rv = diolan_usb_transfer(adapter, buffer, 2, buffer, 2);
> > + if (rv > 0)
> > + *byte = buffer[0];
> > + else if (rv == 0)
> > + rv = -EIO;
> > +
> > + return rv;
> > +}
>
> see notes about stack-mapping buffer.
>
Ok.
> > +static int diolan_i2c_put_byte_ack(struct i2c_adapter *adapter, u8 byte)
> > +{
> > + u8 buffer[2];
> > +
> > + buffer[0] = CMD_I2C_PUT_BYTE_ACK;
> > + buffer[1] = byte;
> > +
> > + return diolan_usb_transfer(adapter, buffer, 2, buffer, 1);
> > +}
> > +
> > +static int diolan_set_speed(struct i2c_adapter *adapter, u8 speed)
> > +{
> > + u8 buffer[2];
> > +
> > + buffer[0] = CMD_I2C_SET_SPEED;
> > + buffer[1] = speed;
> > +
> > + return diolan_usb_transfer(adapter, buffer, 2, buffer, 1);
> > +}
>
> maybe roll-up the 2 byte transfers in the same was a one-byte.
>
Ok.
> > +static int diolan_fw_version(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[3];
> > + int ret;
> > +
> > + buffer[0] = CMD_GET_FW_VERSION;
> > + ret = diolan_usb_transfer(adapter, buffer, 1, buffer, 3);
> > + if (ret == 3)
> > + dev_info(&adapter->dev,
> > + "Diolan U2C firmware version %d.%d\n",
> > + buffer[0], buffer[1]);
> > + return ret;
> > +}
> > +
> > +static int diolan_get_serial(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[5];
> > + int ret;
> > +
> > + buffer[0] = CMD_GET_SERIAL;
> > + ret = diolan_usb_transfer(adapter, buffer, 1, buffer, 5);
> > + if (ret == 5)
> > + dev_info(&adapter->dev,
> > + "Diolan U2C serial number %d\n", *(u32 *) &buffer[0]);
>
> *(u32 *) isn't nice, esp. as you're not going to know the endian-ness of
> the host you are running on. suggest trying a explict le32 ot be32 get of
> the data.
>
Yes, will do.
> > + return ret;
> > +}
>
> > +static int diolan_scan(struct i2c_adapter *adapter)
> > +{
> > + u8 buffer[257];
> > + int i, ret;
>
> suggest kmalloc() the buffer.
>
> > + buffer[0] = CMD_I2C_SCAN;
> > + ret = diolan_usb_transfer(adapter, buffer, 1, buffer, 257);
> > + if (ret > 0) {
> > + for (i = 0; i < ret - 1; i++) {
> > + if (buffer[i])
> > + dev_info(&adapter->dev,
> > + "Found I2C device at address 0x%x\n",
> > + buffer[i] >> 1);
> > + }
> > + }
> > + return ret;
>
> do you really need to do this, we've already got a userspace i2cdetect
> tool?
>
No, dropped.
> > +}
> > +
> > +/* i2c layer */
> > +
> > +static int usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
> > +{
> > + struct i2c_msg *pmsg;
> > + int i, j;
> > + int rc = 0;
> > +
> > + rc = diolan_i2c_start(adapter);
> > + if (rc < 0)
> > + return rc;
> > +
> > + for (i = 0; i < num; i++) {
> > + pmsg = &msgs[i];
> > + if (i) {
> > + rc = diolan_i2c_repeated_start(adapter);
> > + if (rc < 0)
> > + goto abort;
> > + }
> > + if (pmsg->flags & I2C_M_RD) {
> > + rc = diolan_i2c_put_byte_ack(adapter,
> > + ((pmsg->addr & 0x7f) << 1) | 1);
> > + if (rc < 0)
> > + goto abort;
> > + for (j = 0; j < pmsg->len; j++) {
> > + u8 byte;
> > + bool ack = j < pmsg->len - 1;
> > +
> > + /*
> > + * Don't send NACK if this is the first byte
> > + * of a SMBUS_BLOCK message.
> > + */
> > + if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN))
> > + ack = true;
> > +
> > + rc = diolan_i2c_get_byte_ack(adapter, ack,
> > + &byte);
> > + if (rc < 0)
> > + goto abort;
> > + /*
> > + * Adjust count if first received byte is length
> > + */
> > + if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN)) {
> > + if (byte == 0
> > + || byte > I2C_SMBUS_BLOCK_MAX) {
> > + rc = -EREMOTEIO;
> > + goto abort;
> > + }
> > + pmsg->len += byte;
> > + }
> > + pmsg->buf[j] = byte;
> > + }
> > + } else {
> > + rc = diolan_i2c_put_byte_ack(adapter,
> > + (pmsg->addr & 0x7f) << 1);
> > + if (rc < 0)
> > + goto abort;
> > + for (j = 0; j < pmsg->len; j++) {
> > + rc = diolan_i2c_put_byte_ack(adapter,
> > + pmsg->buf[j]);
> > + if (rc < 0)
> > + goto abort;
> > + }
> > + }
> > + }
> > +abort:
> > + diolan_i2c_stop(adapter);
> > + return rc;
> > +}
> > +
> > +/*
> > + * Return list of supported functionality.
> > + */
> > +static u32 usb_func(struct i2c_adapter *a)
> > +{
> > + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
> > + I2C_FUNC_SMBUS_READ_BLOCK_DATA;
> > +}
>
> please make sure everything is prefixed with dio_ for nicer debugging.
>
Ok.
> > +static const struct i2c_algorithm usb_algorithm = {
> > + .master_xfer = usb_xfer,
> > + .functionality = usb_func,
> > +};
> > +
> > +/* device layer */
> > +
> > +static struct usb_device_id i2c_diolan_u2c_table[] = {
> > + {USB_DEVICE(USB_VENDOR_ID_DIOLAN, USB_DEVICE_ID_DIOLAN_U2C)},
>
> spaces between { and text please, same with }
>
Ok.
> > + {}
> > +};
> > +
> > +MODULE_DEVICE_TABLE(usb, i2c_diolan_u2c_table);
> > +
> > +static void i2c_diolan_u2c_free(struct i2c_diolan_u2c *dev)
> > +{
> > + usb_put_dev(dev->usb_dev);
> > + kfree(dev);
> > +}
> > +
> > +static int i2c_diolan_u2c_probe(struct usb_interface *interface,
> > + const struct usb_device_id *id)
> > +{
> > + struct i2c_diolan_u2c *dev;
> > + int retval = -ENOMEM;
> > +
> > + /* allocate memory for our device state and initialize it */
> > + dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> > + if (dev == NULL) {
> > + dev_err(&interface->dev, "Out of memory\n");
> > + goto error;
> > + }
> > +
> > + dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
> > + dev->interface = interface;
> > +
> > + /* save our data pointer in this interface device */
> > + usb_set_intfdata(interface, dev);
> > +
> > + dev_info(&interface->dev,
> > + "Diolan U2C at bus %03d address %03d\n",
> > + dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
> > +
> > + /* setup i2c adapter description */
> > + dev->adapter.owner = THIS_MODULE;
> > + dev->adapter.class = I2C_CLASS_HWMON;
> > + dev->adapter.algo = &usb_algorithm;
> > + dev->adapter.algo_data = dev;
> > + snprintf(dev->adapter.name, sizeof(dev->adapter.name),
> > + "i2c-u2c-usb at bus %03d device %03d",
> > + dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
> > +
> > + dev->adapter.dev.parent = &dev->interface->dev;
> > +
> > + diolan_flush_input(dev->usb_dev);
> > +
> > + /* and finally attach to i2c layer */
> > + i2c_add_adapter(&dev->adapter);
> > +
> > + diolan_fw_version(&dev->adapter);
> > +
> > + retval = diolan_set_speed(&dev->adapter, U2C_I2C_FREQ_STD);
> > + if (retval < 0) {
> > + dev_err(&dev->adapter.dev,
> > + "failure %d setting I2C bus frequency\n", retval);
> > + goto error_del;
> > + }
> > + diolan_get_serial(&dev->adapter);
> > + diolan_scan(&dev->adapter);
>
> do you really need to scan the bus on connection?
No, dropped.
> > + dev_dbg(&dev->adapter.dev, "connected i2c-u2c-usb device\n");
> > +
> > + return 0;
> > +
> > +error_del:
> > + i2c_del_adapter(&dev->adapter);
> > + i2c_diolan_u2c_free(dev);
> > +error:
> > + return retval;
> > +}
> > +
> > +static void i2c_diolan_u2c_disconnect(struct usb_interface *interface)
> > +{
> > + struct i2c_diolan_u2c *dev = usb_get_intfdata(interface);
> > +
> > + i2c_del_adapter(&dev->adapter);
> > + usb_set_intfdata(interface, NULL);
> > + i2c_diolan_u2c_free(dev);
> > +
> > + dev_dbg(&interface->dev, "disconnected\n");
> > +}
> > +
> > +static struct usb_driver i2c_diolan_u2c_driver = {
> > + .name = "i2c-u2c-usb",
> > + .probe = i2c_diolan_u2c_probe,
> > + .disconnect = i2c_diolan_u2c_disconnect,
> > + .id_table = i2c_diolan_u2c_table,
> > +};
> > +
> > +static int __init usb_i2c_diolan_u2c_init(void)
> > +{
> > + /* register this driver with the USB subsystem */
> > + return usb_register(&i2c_diolan_u2c_driver);
> > +}
> > +
> > +static void __exit usb_i2c_diolan_u2c_exit(void)
> > +{
> > + /* deregister this driver with the USB subsystem */
> > + usb_deregister(&i2c_diolan_u2c_driver);
> > +}
> > +
> > +module_init(usb_i2c_diolan_u2c_init);
> > +module_exit(usb_i2c_diolan_u2c_exit);
> > +
> > +/* ----- end of usb layer ------------------------------------------------ */
> > +
> > +MODULE_AUTHOR("Guenter Roeck <guenter.roeck@...csson.com>");
> > +MODULE_DESCRIPTION("i2c-u2c-usb driver");
> > +MODULE_LICENSE("GPL");
>
> --
> Ben
>
> Q: What's a light-year?
> A: One-third less calories than a regular year.
>
Thanks a lot for the review!
Guenter
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