Am 11.12.2014 16:36, schrieb Bartosz Golaszewski:
> This version includes fixes suggested for v1 and implements i2cset. Any
> testing and suggestions for size reduction are welcome.
> 
> Next: i2cdump and i2cdetect.
> 
> v1:
> http://lists.busybox.net/pipermail/busybox/2014-December/082071.html
> 
> Signed-off-by: Bartosz Golaszewski <bartekg...@gmail.com>
> ---
>  miscutils/i2c_tools.c | 727 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 727 insertions(+)
>  create mode 100644 miscutils/i2c_tools.c
> 
> diff --git a/miscutils/i2c_tools.c b/miscutils/i2c_tools.c
> new file mode 100644
> index 0000000..ad04e0d
> --- /dev/null
> +++ b/miscutils/i2c_tools.c
> @@ -0,0 +1,727 @@
> +/* vi: set sw=4 ts=4: */
> +/*
> + * Minimal i2c-tools implementation for busybox.
> + * Parts of code ported from i2c-tools:
> + *           http://www.lm-sensors.org/wiki/I2CTools.
> + *
> + * Copyright (C) 2014 by Bartosz Golaszewski <bartekg...@gmail.com>
> + *
> + * Licensed under GPLv2 or later, see file LICENSE in this source tree.
> + */
> +
> +//config:config I2CGET
> +//config:    bool "i2cget"
> +//config:    default y
> +//config:    select PLATFORM_LINUX
> +//config:    help
> +//config:      Read from I2C/SMBus chip registers.
> +//config:
> +//config:config I2CSET
> +//config:    bool "i2cset"
> +//config:    default y
> +//config:    select PLATFORM_LINUX
> +//config:    help
> +//config:      Set I2C registers.
> +//config:
> +
> +//applet:IF_I2CGET(APPLET(i2cget, BB_DIR_USR_SBIN, BB_SUID_DROP))
> +//applet:IF_I2CSET(APPLET(i2cset, BB_DIR_USR_SBIN, BB_SUID_DROP))
> +
> +//kbuild:lib-$(CONFIG_I2CGET) += i2c_tools.o
> +//kbuild:lib-$(CONFIG_I2CSET) += i2c_tools.o
> +
> +//usage:#define i2cget_trivial_usage
> +//usage:       "[-f] [-y] BUS CHIP-ADDRESS [DATA-ADDRESS [MODE]]"
> +//usage:#define i2cget_full_usage "\n\n"
> +//usage:       "Read from I2C/SMBus chip registers\n"
> +//usage:     "\n  I2CBUS is an i2c bus number"
> +//usage:     "\n  ADDRESS is an integer (0x03 - 0x77)"
> +//usage:     "\n  MODE is one of:"
> +//usage:     "\n    b (read byte data, default)"
> +//usage:     "\n    w (read word data)"
> +//usage:     "\n    c (write byte/read byte)"
> +//usage:   "\n\n  Append p for SMBus PEC"
> +//usage:   "\n\n  -f - force access to device"
> +//usage:     "\n  -y - disable interactive mode"
> +//usage:
> +//usage:#define i2cset_trivial_usage
> +//usage:       "[-f] [-y] [-m MASK] BUS CHIP-ADDR DATA-ADDR [VALUE] ... 
> [MODE]"
> +//usage:#define i2cset_full_usage "\n\n"
> +//usage:       "Set I2C registers\n"
> +//usage:     "\n  I2CBUS is an i2c bus number"
> +//usage:     "\n  ADDRESS is an integer (0x03 - 0x77)"
> +//usage:     "\n  MODE is one of:"
> +//usage:     "\n    c (byte, no value)"
> +//usage:     "\n    b (byte data, default)"
> +//usage:     "\n    w (word data)"
> +//usage:     "\n    i (I2C block data)"
> +//usage:     "\n    s (SMBus block data)"
> +//usage:   "\n\n  Append p for SMBus PEC"
> +//usage:   "\n\n  -f - force access to device"
> +//usage:     "\n  -y - disable interactive mode"
> +//usage:     "\n  -r - read back and compare the result"
> +//usage:     "\n  -m - mask specifying which bits to write"
> +//usage:
> +
> +#include "libbb.h"
> +
> +/*
> + * /dev/i2c-X ioctl commands. The ioctl's parameter is always an unsigned 
> long,
> + * except for:
> + *    - I2C_FUNCS, takes pointer to an unsigned long
> + *    - I2C_RDWR, takes pointer to struct i2c_rdwr_ioctl_data
> + *    - I2C_SMBUS, takes pointer to struct i2c_smbus_ioctl_data
> + */
> +
> +/* Number of times a device address should be polled when not acknowledging 
> */
> +#define I2C_RETRIES  0x0701
> +/* Set timeout in units of 10 ms */
> +#define I2C_TIMEOUT  0x0702
> +
> +/*
> + * NOTE: Slave address is 7 or 10 bits, but 10-bit addresses
> + * are NOT supported! (due to code brokenness)
> + */
> +
> +/* Use this slave address */
> +#define I2C_SLAVE    0x0703
> +/* Use this slave address, even if it is already in use by a driver! */
> +#define I2C_SLAVE_FORCE      0x0706
> +/* 0 for 7 bit addrs, != 0 for 10 bit */
> +#define I2C_TENBIT   0x0704
> +/* Get the adapter functionality mask */
> +#define I2C_FUNCS    0x0705
> +/* Combined R/W transfer (one STOP only) */
> +#define I2C_RDWR     0x0707
> +/* != 0 to use PEC with SMBus */
> +#define I2C_PEC              0x0708
> +/* SMBus transfer */
> +#define I2C_SMBUS    0x0720
> +
> +/* This is the structure as used in the I2C_SMBUS ioctl call */
> +struct i2c_smbus_ioctl_data {
> +     uint8_t read_write;
> +     uint8_t command;
> +     uint32_t size;
> +     union i2c_smbus_data *data;
> +};
> +
> +/* This is the structure as used in the I2C_RDWR ioctl call */
> +struct i2c_rdwr_ioctl_data {
> +     struct i2c_msg *msgs;   /* pointers to i2c_msgs */
> +     uint32_t nmsgs;                 /* number of i2c_msgs */
> +};
> +
> +/* As specified in SMBus standard */
> +#define I2C_SMBUS_BLOCK_MAX          32
> +/* Not specified but we use same structure */
> +#define I2C_SMBUS_I2C_BLOCK_MAX              32
> +
> +/*
> + * Data for SMBus Messages
> + */
> +union i2c_smbus_data {
> +     uint8_t byte;
> +     uint16_t word;
> +     /* block[0] is used for length and one more for PEC */
> +     uint8_t block[I2C_SMBUS_BLOCK_MAX + 2];
> +};
> +
> +#define  I2C_RDRW_IOCTL_MAX_MSGS     42
> +
> +/* smbus_access read or write markers */
> +#define I2C_SMBUS_READ       1
> +#define I2C_SMBUS_WRITE      0
> +
> +/* SMBus transaction types (size parameter in the below functions). */
> +#define I2C_SMBUS_QUICK                      0
> +#define I2C_SMBUS_BYTE                       1
> +#define I2C_SMBUS_BYTE_DATA          2
> +#define I2C_SMBUS_WORD_DATA          3
> +#define I2C_SMBUS_PROC_CALL          4
> +#define I2C_SMBUS_BLOCK_DATA         5
> +#define I2C_SMBUS_I2C_BLOCK_BROKEN   6
> +#define I2C_SMBUS_BLOCK_PROC_CALL    7
> +#define I2C_SMBUS_I2C_BLOCK_DATA     8
> +
> +/* Defines to determine what functionality is present */
> +#define I2C_FUNC_I2C                         0x00000001
> +#define I2C_FUNC_10BIT_ADDR                  0x00000002
> +#define I2C_FUNC_PROTOCOL_MANGLING           0x00000004
> +#define I2C_FUNC_SMBUS_PEC                   0x00000008
> +#define I2C_FUNC_SMBUS_BLOCK_PROC_CALL               0x00008000
> +#define I2C_FUNC_SMBUS_QUICK                 0x00010000
> +#define I2C_FUNC_SMBUS_READ_BYTE             0x00020000
> +#define I2C_FUNC_SMBUS_WRITE_BYTE            0x00040000
> +#define I2C_FUNC_SMBUS_READ_BYTE_DATA                0x00080000
> +#define I2C_FUNC_SMBUS_WRITE_BYTE_DATA               0x00100000
> +#define I2C_FUNC_SMBUS_READ_WORD_DATA                0x00200000
> +#define I2C_FUNC_SMBUS_WRITE_WORD_DATA               0x00400000
> +#define I2C_FUNC_SMBUS_PROC_CALL             0x00800000
> +#define I2C_FUNC_SMBUS_READ_BLOCK_DATA               0x01000000
> +#define I2C_FUNC_SMBUS_WRITE_BLOCK_DATA      0x02000000
> +#define I2C_FUNC_SMBUS_READ_I2C_BLOCK                0x04000000
> +#define I2C_FUNC_SMBUS_WRITE_I2C_BLOCK               0x08000000
> +
> +/*
> + * This is needed for ioctl_or_perror_and_die() since it only accepts 
> pointer.
> + */
> +#define INT_TO_PTR(i) ((void*)((long)i))
> +
> +static int32_t i2c_smbus_access(int fd, char read_write, uint8_t cmd,
> +                             int size, union i2c_smbus_data *data)
> +{
> +     struct i2c_smbus_ioctl_data args;
> +
> +     args.read_write = read_write;
> +     args.command = cmd;
> +     args.size = size;
> +     args.data = data;
> +
> +     return ioctl(fd, I2C_SMBUS, &args);
> +}
> +
> +static int32_t i2c_smbus_read_byte(int fd)
> +{
> +     union i2c_smbus_data data;
> +     int err;
> +
> +     err = i2c_smbus_access(fd, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data);
> +     if (err < 0)
> +             return err;
> +
> +     return 0xff & data.byte;
> +}
> +
> +static int32_t i2c_smbus_write_byte(int fd, uint8_t val)
> +{
> +     return i2c_smbus_access(fd, I2C_SMBUS_WRITE,
> +                             val, I2C_SMBUS_BYTE, NULL);
> +}
> +
> +static int32_t i2c_smbus_read_byte_data(int fd, uint8_t cmd)
> +{
> +     union i2c_smbus_data data;
> +     int err;
> +
> +     err = i2c_smbus_access(fd, I2C_SMBUS_READ, cmd,
> +                            I2C_SMBUS_BYTE_DATA, &data);
> +     if (err < 0)
> +             return err;
> +
> +     return 0xff & data.byte;
> +}
> +
> +static int32_t i2c_smbus_read_word_data(int fd, uint8_t cmd)
> +{
> +     union i2c_smbus_data data;
> +     int err;
> +
> +     err = i2c_smbus_access(fd, I2C_SMBUS_READ, cmd,
> +                            I2C_SMBUS_WORD_DATA, &data);
> +     if (err < 0)
> +             return err;
> +
> +     return 0xffff & data.word;
> +}
> +
> +#if ENABLE_I2CSET
> +static int32_t i2c_smbus_write_byte_data(int file,
> +                                      uint8_t cmd, uint8_t value)
> +{
> +     union i2c_smbus_data data;
> +
> +     data.byte = value;
> +
> +     return i2c_smbus_access(file, I2C_SMBUS_WRITE, cmd,
> +                             I2C_SMBUS_BYTE_DATA, &data);
> +}
> +
> +static int32_t i2c_smbus_write_word_data(int file, uint8_t cmd, uint16_t 
> value)
> +{
> +     union i2c_smbus_data data;
> +
> +     data.word = value;
> +
> +     return i2c_smbus_access(file, I2C_SMBUS_WRITE, cmd,
> +                             I2C_SMBUS_WORD_DATA, &data);
> +}
> +
> +static int32_t i2c_smbus_write_block_data(int file, uint8_t cmd,
> +                                uint8_t length, const uint8_t *values)
> +{
> +     union i2c_smbus_data data;
> +     int i;
> +
> +     if (length > I2C_SMBUS_BLOCK_MAX)
> +             length = I2C_SMBUS_BLOCK_MAX;
> +     for (i = 1; i <= length; i++)
> +             data.block[i] = values[i-1];
> +     data.block[0] = length;
> +
> +     return i2c_smbus_access(file, I2C_SMBUS_WRITE, cmd,
> +                             I2C_SMBUS_BLOCK_DATA, &data);
> +}
> +
> +static int32_t i2c_smbus_write_i2c_block_data(int file, uint8_t cmd,
> +                                    uint8_t length, const uint8_t *values)
> +{
> +     union i2c_smbus_data data;
> +     int i;
> +
> +     if (length > I2C_SMBUS_BLOCK_MAX)
> +             length = I2C_SMBUS_BLOCK_MAX;
> +     for (i = 1; i <= length; i++)
> +             data.block[i] = values[i-1];

I have no idea how often this is uses but perhaps it is useful
to copy the whole block in once instead of byte wise.
memcpy(data.block+1,values,length); /* untested */
(Same above)


> +     data.block[0] = length;

> +
> +     return i2c_smbus_access(file, I2C_SMBUS_WRITE, cmd,
> +                             I2C_SMBUS_I2C_BLOCK_BROKEN, &data);
> +}
> +#endif /* ENABLE_I2CSET */
> +
> +static int i2c_bus_lookup(const char *bus_str)
> +{
> +     return xstrtoi_range(bus_str, 10, 0, 0xfffff);
> +}
> +
> +static int i2c_parse_bus_addr(const char *addr_str)
> +{
> +     return xstrtoi_range(addr_str, 16, 0x03, 0x77);
> +}
> +
> +static int i2c_parse_data_addr(const char *data_addr)
> +{
> +     return xstrtoi_range(data_addr, 16, 0, 0xff);
> +}
i am not an i2c expert, can you drop a comment here about the magic numbers ?



> +/* Opens the device file associated with given i2c bus. */
> +static int i2c_dev_open(int i2cbus)
> +{
> +     char filename[32];
> +     int fd;
> +
> +     snprintf(filename, sizeof(filename), "/dev/i2c-%d", i2cbus);
> +     fd = open_or_warn(filename, O_RDWR);

now user of "/dev/i2c/%d" get warning here even when the next open works.
I do not think that this was you intention.


/* having one open is more easy :) */

just my 2 cents,
 wh

> +     if (fd < 0 && errno == ENOENT) {
> +             snprintf(filename, sizeof(filename), "/dev/i2c/%d", i2cbus);
> +             fd = xopen(filename, O_RDWR);
> +     }
> +
> +     return fd;
> +}
> +
> +static void i2c_set_slave_addr(int fd, int addr, int force)
> +{
> +     ioctl_or_perror_and_die(fd, force ? I2C_SLAVE_FORCE : I2C_SLAVE,
> +                             INT_TO_PTR(addr),
> +                             "Could not set address to 0x%02x", addr);
> +}
> +
> +static void i2c_set_pec(int fd, int pec)
> +{
> +     ioctl_or_perror_and_die(fd, I2C_PEC,
> +                             INT_TO_PTR(pec ? 1 : 0),
> +                             "Could not set PEC");
> +}
> +
> +/* Size reducing helpers for xxx_check_funcs(). */
> +static void get_funcs_matrix(int fd, unsigned long *funcs)
> +{
> +     ioctl_or_perror_and_die(fd, I2C_FUNCS, funcs,
> +                     "Could not get the adapter functionality matrix");
> +}
> +
> +static void check_funcs_test_end(int funcs, int pec, const char *err)
> +{
> +     if (pec && !(funcs & (I2C_FUNC_SMBUS_PEC | I2C_FUNC_I2C)))
> +             fprintf(stderr,
> +                     "Warning: Adapter does not seem to support PEC\n");
> +
> +     if (err)
> +             bb_error_msg_and_die("Adapter does not have %s capability",
> +                                  err);
> +}
> +
> +/*
> + * The below functions emit an error message and exit if the adapter doesn't
> + * support desired functionalities.
> + */
> +#if ENABLE_I2CGET
> +static void i2cget_check_funcs(int fd, int mode, int data_addr, int pec)
> +{
> +     unsigned long funcs;
> +     const char *err = NULL;
> +
> +     get_funcs_matrix(fd, &funcs);
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE:
> +             if (!(funcs & I2C_FUNC_SMBUS_READ_BYTE)) {
> +                     err = "SMBus receive byte";
> +                     break;
> +             }
> +             if (data_addr >= 0 && !(funcs & I2C_FUNC_SMBUS_WRITE_BYTE))
> +                     err = "SMBus send byte";
> +             break;
> +     case I2C_SMBUS_BYTE_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_READ_BYTE_DATA))
> +                     err = "SMBus read byte";
> +             break;
> +     case I2C_SMBUS_WORD_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_READ_WORD_DATA))
> +                     err = "SMBus read word";
> +             break;
> +     }
> +     check_funcs_test_end(funcs, pec, err);
> +}
> +#endif /* ENABLE_I2CGET */
> +
> +#if ENABLE_I2CSET
> +static void i2cset_check_funcs(int fd, int mode, int pec)
> +{
> +     unsigned long funcs;
> +     const char *err = NULL;
> +
> +     get_funcs_matrix(fd, &funcs);
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE:
> +             if (!(funcs & I2C_FUNC_SMBUS_WRITE_BYTE))
> +                     err = "SMBus send byte";
> +             break;
> +
> +     case I2C_SMBUS_BYTE_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
> +                     err = "SMBus write byte";
> +             break;
> +
> +     case I2C_SMBUS_WORD_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_WRITE_WORD_DATA))
> +                     err = "SMBus write word";
> +             break;
> +
> +     case I2C_SMBUS_BLOCK_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_WRITE_BLOCK_DATA))
> +                     err = "SMBus block write";
> +             break;
> +     case I2C_SMBUS_I2C_BLOCK_DATA:
> +             if (!(funcs & I2C_FUNC_SMBUS_WRITE_I2C_BLOCK))
> +                     err = "I2C block write";
> +             break;
> +     }
> +     check_funcs_test_end(funcs, pec, err);
> +}
> +#endif /* ENABLE_I2CSET */
> +
> +/*********************************** XXXX 
> ***********************************/
> +/*
> + * XXX read_line() exists already in util-linux/fdisk.c - move it to
> + * libbb and reuse here in the final version of the patch. This will save
> + * additional 116 bytes.
> + */
> +static char *line_ptr;
> +static char line_buffer[128];
> +
> +static int read_line(const char *prompt)
> +{
> +     int sz;
> +
> +     sz = read_line_input(NULL, prompt, line_buffer,
> +                          sizeof(line_buffer), /*timeout*/ -1);
> +     if (sz <= 0)
> +             exit(EXIT_SUCCESS); /* Ctrl-D or Ctrl-C */
> +
> +     if (line_buffer[sz-1] == '\n')
> +             line_buffer[--sz] = '\0';
> +
> +     line_ptr = line_buffer;
> +     while (*line_ptr != '\0' && (unsigned char)*line_ptr <= ' ')
> +             line_ptr++;
> +     return *line_ptr;
> +}
> +
> +static void user_confirm(void)
> +{
> +     if (tolower(read_line("Continue? [y/N] ")) != 'y') {
> +             fprintf(stderr, "Aborting.\n");
> +             xfunc_die();
> +     }
> +}
> +/*********************************** XXXX 
> ***********************************/
> +
> +/*
> + * Return only if user confirms the action, abort otherwise.
> + *
> + * The messages displayed here are much less elaborate than their i2c-tools
> + * counterparts - this is done for size reduction.
> + */
> +static void confirm_action(int bus_addr, int mode, int data_addr, int pec)
> +{
> +     fprintf(stderr, "WARNING! This program can confuse your I2C bus\n");
> +
> +     /* Don't let the user break his/her EEPROMs */
> +     if (bus_addr >= 0x50 && bus_addr <= 0x57 && pec) {
> +             fprintf(stderr, "This is I2C not smbus - using PEC on I2C "
> +                     "devices may result in data loss. Aborting.\n");
> +             xfunc_die();
> +     }
> +
> +     if (mode == I2C_SMBUS_BYTE && data_addr >= 0 && pec)
> +             fprintf(stderr, "WARNING! May interpret a write byte command "
> +                     "with PEC as a write byte data command!\n");
> +
> +     if (pec)
> +             fprintf(stderr, "PEC checking enabled.\n");
> +
> +     user_confirm();
> +}
> +
> +#if ENABLE_I2CGET
> +int i2cget_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> +int i2cget_main(int argc, char **argv)
> +{
> +     static const unsigned opt_f = (1 << 0), opt_y = (1 << 1);
> +     static const char *const optstr = "fy";
> +
> +     int bus_num, bus_addr, data_addr = -1, status;
> +     int mode = I2C_SMBUS_BYTE, pec = 0, fd;
> +     unsigned opts;
> +
> +     opts = getopt32(argv, optstr);
> +     argv += optind;
> +     argc -= optind;
> +
> +     if (argc < 2)
> +             bb_show_usage();
> +
> +     bus_num = i2c_bus_lookup(argv[0]);
> +     bus_addr = i2c_parse_bus_addr(argv[1]);
> +
> +     if (argc > 2) {
> +             data_addr = i2c_parse_data_addr(argv[2]);
> +             mode = I2C_SMBUS_BYTE_DATA;
> +     }
> +
> +     if (argc > 3) {
> +             switch (argv[3][0]) {
> +             case 'b':       /* Already set */               break;
> +             case 'w':       mode = I2C_SMBUS_WORD_DATA;     break;
> +             case 'c':       mode = I2C_SMBUS_BYTE;          break;
> +             default:
> +                     bb_error_msg("Invalid mode");
> +                     bb_show_usage();
> +             }
> +             pec = argv[3][1] == 'p';
> +     }
> +
> +     fd = i2c_dev_open(bus_num);
> +     i2cget_check_funcs(fd, mode, data_addr, pec);
> +     i2c_set_slave_addr(fd, bus_addr, opts & opt_f);
> +
> +     if (!(opts & opt_y))
> +             confirm_action(bus_addr, mode, data_addr, pec);
> +
> +     if (pec)
> +             i2c_set_pec(fd, 1);
> +
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE:
> +             if (data_addr >= 0) {
> +                     status = i2c_smbus_write_byte(fd, data_addr);
> +                     if (status < 0)
> +                             fprintf(stderr, "Warning - write failed\n");
> +             }
> +             status = i2c_smbus_read_byte(fd);
> +             break;
> +     case I2C_SMBUS_WORD_DATA:
> +             status = i2c_smbus_read_word_data(fd, data_addr);
> +             break;
> +     default: /* I2C_SMBUS_BYTE_DATA */
> +             status = i2c_smbus_read_byte_data(fd, data_addr);
> +     }
> +     close(fd);
> +
> +     if (status < 0)
> +             bb_perror_msg_and_die("Read failed");
> +
> +     printf("0x%0*x\n", mode == I2C_SMBUS_WORD_DATA ? 4 : 2, status);
> +
> +     return 0;
> +}
> +#endif /* ENABLE_I2CGET */
> +
> +#if ENABLE_I2CSET
> +int i2cset_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> +int i2cset_main(int argc, char **argv)
> +{
> +     static const unsigned opt_f = (1 << 0), opt_y = (1 << 1),
> +                           opt_m = (1 << 2), opt_r = (1 << 3);
> +     static const char *const optstr = "fym:r";
> +
> +     int bus_num, bus_addr, data_addr, mode = I2C_SMBUS_BYTE, pec = 0;
> +     int val, blen = 0, mask = 0, fd, status;
> +     unsigned char block[I2C_SMBUS_BLOCK_MAX];
> +     char *opt_m_arg = NULL;
> +     unsigned opts;
> +
> +     opts = getopt32(argv, optstr, &opt_m_arg);
> +     argv += optind;
> +     argc -= optind;
> +
> +     if (argc < 3)
> +             bb_show_usage();
> +
> +     bus_num = i2c_bus_lookup(argv[0]);
> +     bus_addr = i2c_parse_bus_addr(argv[1]);
> +     data_addr = i2c_parse_data_addr(argv[2]);
> +
> +     if (argc > 3) {
> +             switch (argv[argc-1][0]) {
> +             case 'c': mode = I2C_SMBUS_BYTE;                break;
> +             case 'b': mode = I2C_SMBUS_BYTE_DATA;           break;
> +             case 'w': mode = I2C_SMBUS_WORD_DATA;           break;
> +             case 's': mode = I2C_SMBUS_BLOCK_DATA;          break;
> +             case 'i': mode = I2C_SMBUS_I2C_BLOCK_DATA;      break;
> +             default:
> +                     bb_error_msg("Invalid mode");
> +                     bb_show_usage();
> +             }
> +             pec = argv[argc-1][1] == 'p';
> +             if (mode == I2C_SMBUS_BLOCK_DATA ||
> +                             mode == I2C_SMBUS_I2C_BLOCK_DATA) {
> +                     if (pec && mode == I2C_SMBUS_I2C_BLOCK_DATA)
> +                             bb_error_msg_and_die("PEC not supported for "
> +                                                  "I2C block writes!");
> +                     if (opts & opt_m)
> +                             bb_error_msg_and_die("Mask not supported "
> +                                                  "for block writes!\n");
> +             }
> +     }
> +
> +     /* Prepare the value(s) to be written according to current mode. */
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE_DATA:
> +             val = xstrtoi_range(argv[3], 0, 0, 0xff);
> +             break;
> +     case I2C_SMBUS_WORD_DATA:
> +             val = xstrtoi_range(argv[3], 0, 0, 0xffff);
> +             break;
> +     case I2C_SMBUS_BLOCK_DATA:
> +     case I2C_SMBUS_I2C_BLOCK_DATA:
> +             for (blen = 3; blen < (argc - 1); blen++)
> +                     block[blen] = xstrtoi_range(argv[blen], 0, 0, 0xff);
> +             val = -1;
> +             break;
> +     default:
> +             val = -1;
> +             break;
> +     }
> +
> +     if (opts & opt_m) {
> +             mask = xstrtoi_range(opt_m_arg, 0, 0,
> +                             (mode == I2C_SMBUS_BYTE ||
> +                              mode == I2C_SMBUS_BYTE_DATA) ? 0xff : 0xffff);
> +     }
> +
> +     fd = i2c_dev_open(bus_num);
> +     i2cset_check_funcs(fd, mode, pec);
> +     i2c_set_slave_addr(fd, bus_addr, opts & opt_f);
> +
> +     if (!(opts & opt_y))
> +             confirm_action(bus_addr, mode, data_addr, pec);
> +
> +     /*
> +      * If we're using mask - read the current value here and adjust the
> +      * value to be written.
> +      */
> +     if (opts & opt_m) {
> +             int tmpval;
> +
> +             switch (mode) {
> +             case I2C_SMBUS_BYTE:
> +                     tmpval = i2c_smbus_read_byte(fd);
> +                     break;
> +             case I2C_SMBUS_WORD_DATA:
> +                     tmpval = i2c_smbus_read_word_data(fd, data_addr);
> +                     break;
> +             default:
> +                     tmpval = i2c_smbus_read_byte_data(fd, data_addr);
> +             }
> +
> +             if (tmpval < 0)
> +                     bb_perror_msg_and_die("Failed to read old value");
> +
> +             val = (val & mask) | (tmpval & ~mask);
> +
> +             if (!(opts & opt_y)) {
> +                     fprintf(stderr, "Old value 0x%0*x, write mask "
> +                             "0x%0*x: Will write 0x%0*x to register "
> +                             "0x%02x\n",
> +                             mode == I2C_SMBUS_WORD_DATA ? 4 : 2, tmpval,
> +                             mode == I2C_SMBUS_WORD_DATA ? 4 : 2, mask,
> +                             mode == I2C_SMBUS_WORD_DATA ? 4 : 2, val,
> +                             data_addr);
> +
> +                     user_confirm();
> +             }
> +     }
> +
> +     if (pec)
> +             i2c_set_pec(fd, 1);
> +
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE:
> +             status = i2c_smbus_write_byte(fd, data_addr);
> +             break;
> +     case I2C_SMBUS_WORD_DATA:
> +             status = i2c_smbus_write_word_data(fd, data_addr, val);
> +             break;
> +     case I2C_SMBUS_BLOCK_DATA:
> +             status = i2c_smbus_write_block_data(fd, data_addr,
> +                                                 blen, block);
> +             break;
> +     case I2C_SMBUS_I2C_BLOCK_DATA:
> +             status = i2c_smbus_write_i2c_block_data(fd, data_addr,
> +                                                     blen, block);
> +             break;
> +     default: /* I2C_SMBUS_BYTE_DATA */
> +             status = i2c_smbus_write_byte_data(fd, data_addr, val);
> +             break;
> +     }
> +     if (status < 0)
> +             bb_perror_msg_and_die("Write failed\n");
> +
> +     if (pec)
> +             i2c_set_pec(fd, 0); /* Clear PEC */
> +
> +     /* No readback required - we're done. */
> +     if (!(opts & opt_r))
> +             return 0;
> +
> +     switch (mode) {
> +     case I2C_SMBUS_BYTE:
> +             status = i2c_smbus_read_byte(fd);
> +             val = data_addr;
> +             break;
> +     case I2C_SMBUS_WORD_DATA:
> +             status = i2c_smbus_read_word_data(fd, data_addr);
> +             break;
> +     default: /* I2C_SMBUS_BYTE_DATA */
> +             status = i2c_smbus_read_byte_data(fd, data_addr);
> +     }
> +
> +     if (status < 0) {
> +             printf("Warning - readback failed\n");
> +     } else
> +     if (status != val) {
> +             printf("Warning - data mismatch - wrote "
> +                    "0x%0*x, read back 0x%0*x\n",
> +                    mode == I2C_SMBUS_WORD_DATA ? 4 : 2, val,
> +                    mode == I2C_SMBUS_WORD_DATA ? 4 : 2, status);
> +     } else {
> +             printf("Value 0x%0*x written, readback matched\n",
> +                    mode == I2C_SMBUS_WORD_DATA ? 4 : 2, val);
> +     }
> +
> +     return 0;
> +}
> +#endif /* ENABLE_I2CSET */
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