Re: [PATCH v2 1/4] tools: iio: Move printf failure messages to stderr

[Hartmut Knaack]

Cristina Georgiana Opriceana schrieb am 12.07.2015 um 13:38:
> On Sat, Jul 11, 2015 at 12:42 AM, Hartmut Knaack <knaack.h@xxxxxx> wrote:
>> Cristina Opriceana schrieb am 10.07.2015 um 12:56:
>>> Replace printf error messages with fprintf(stderr, ...) in order
>>> to ensure consistency and to make faults easier to identify.
>>> This patch uses coccinelle to detect and apply the changes.
>>>
>>
>> Hi Cristina,
>> I just had a look at the series. You have all cases I regard necessary
>> covered. There are however a few cases which probably qualify as error
>> messages, too. Please see inline.
>> However, for my personal taste, this could have been merged all in a
>> single patch. Especially the third patch should have been included in
>> this one (as during review, people certainly think that you missed the
>> second line, just to find it fixed two patches later).
> 
> Hi,
> 
> Yes, I could have included all in a single patch, but I tried to
> automatize this task and build a rather generic semantic patch in
> coccinelle for the substitutions. Had I included all in one patch, the
> changes with coccinelle wouldn't have been differentiated from the
> other ones. If that is okay, I think I can merge them in one patch.
> 

Point taken for making it reproducible. I just like to raise awareness:
The maintainers are very busy. They have a full time job, respond to the
mailing list, review patches and do all the git magic. That keeps them
pretty busy, so I would aim to make the maintainers life as easy as possible.
Checking just one patch against some sources can be quicker/easier than
checking multiple ones. Same goes for applying patches.
Other than that, I just feel strong about the third patch standing separate,
which I don't regard a good idea. Either your script should have been
extended to catch such cases, or if it is not worth the effort, it should
have been changed by hand. But it should have gone in one pass.

>>> Signed-off-by: Cristina Opriceana <cristina.opriceana@xxxxxxxxx>
>>> ---
>>> Changes in v2:
>>>  - s/failiure/failure
>>>
>>>  tools/iio/generic_buffer.c    | 17 ++++++++++-------
>>>  tools/iio/iio_event_monitor.c |  6 +++---
>>>  tools/iio/iio_utils.c         | 34 ++++++++++++++++++++--------------
>>>  3 files changed, 33 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
>>> index 0e73723..2f4e12f 100644
>>> --- a/tools/iio/generic_buffer.c
>>> +++ b/tools/iio/generic_buffer.c
>>> @@ -271,7 +271,7 @@ int main(int argc, char **argv)
>>>       }
>>>
>>>       if (device_name == NULL) {
>>> -             printf("Device name not set\n");
>>> +             fprintf(stderr, "Device name not set\n");
>>>               print_usage();
>>>               return -1;
>>>       }
>>> @@ -279,7 +279,7 @@ int main(int argc, char **argv)
>>>       /* Find the device requested */
>>>       dev_num = find_type_by_name(device_name, "iio:device");
>>>       if (dev_num < 0) {
>>> -             printf("Failed to find the %s\n", device_name);
>>> +             fprintf(stderr, "Failed to find the %s\n", device_name);
>>>               return dev_num;
>>>       }
>>>
>>> @@ -307,7 +307,8 @@ int main(int argc, char **argv)
>>>               /* Verify the trigger exists */
>>>               trig_num = find_type_by_name(trigger_name, "trigger");
>>>               if (trig_num < 0) {
>>> -                     printf("Failed to find the trigger %s\n", trigger_name);
>>> +                     fprintf(stderr, "Failed to find the trigger %s\n",
>>> +                             trigger_name);
>>>                       ret = trig_num;
>>>                       goto error_free_triggername;
>>>               }
>>> @@ -323,7 +324,7 @@ int main(int argc, char **argv)
>>>        */
>>>       ret = build_channel_array(dev_dir_name, &channels, &num_channels);
>>>       if (ret) {
>>> -             printf("Problem reading scan element information\n");
>>> +             fprintf(stderr, "Problem reading scan element information\n");
>>>               printf("diag %s\n", dev_dir_name);
>>
>> My preference would even be to print it all in just one fprintf.
> 
> I thought so, also, but the string would go beyond 80 characters and
> would have to be split which is ugly and brings a warning on it.
> 

I just gave it a try compile testing:
		fprintf(stderr, "Problem reading scan element information\n"
			"diag %s\n", dev_dir_name);

Compiled just fine, and the same format is used in your second patch as well.

>>>               goto error_free_triggername;
>>>       }
>>> @@ -350,7 +351,8 @@ int main(int argc, char **argv)
>>>                                                   dev_dir_name,
>>>                                                   trigger_name);
>>>               if (ret < 0) {
>>> -                     printf("Failed to write current_trigger file\n");
>>> +                     fprintf(stderr,
>>> +                             "Failed to write current_trigger file\n");
>>>                       goto error_free_buf_dir_name;
>>>               }
>>>       }
>>> @@ -382,7 +384,7 @@ int main(int argc, char **argv)
>>>       fp = open(buffer_access, O_RDONLY | O_NONBLOCK);
>>>       if (fp == -1) { /* TODO: If it isn't there make the node */
>>>               ret = -errno;
>>> -             printf("Failed to open %s\n", buffer_access);
>>> +             fprintf(stderr, "Failed to open %s\n", buffer_access);
>>>               goto error_free_buffer_access;
>>>       }
>>>
>>
>> At line 410 we have a block:
>>                 read_size = read(fp, data, toread * scan_size);
>>                 if (read_size < 0) {
>>                         if (errno == EAGAIN) {
>>                                 printf("nothing available\n");
>>                                 continue;
>>
>> I'm tempted to say,that this should go to stderr, as well. Any opinions?
> 
> I see it more as an informing note, since the device continues looping
> for data, but it could be considered an error as well.

I thought about the case when stdout gets piped to a data file while stderr
goes into a logfile (or an application reads one data stream while checking
the error stream).

> 
>>> @@ -431,7 +433,8 @@ int main(int argc, char **argv)
>>>               ret = write_sysfs_string("trigger/current_trigger",
>>>                                        dev_dir_name, "NULL");
>>>               if (ret < 0)
>>> -                     printf("Failed to write to %s\n", dev_dir_name);
>>> +                     fprintf(stderr, "Failed to write to %s\n",
>>> +                             dev_dir_name);
>>>
>>>  error_close_buffer_access:
>>>       if (close(fp) == -1)
>>> diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
>>> index 703f4cb..843bc4c 100644
>>> --- a/tools/iio/iio_event_monitor.c
>>> +++ b/tools/iio/iio_event_monitor.c
>>
>> At line 217:
>>         if (!event_is_known(event)) {
>>                 printf("Unknown event: time: %lld, id: %llx\n",
>>                        event->timestamp, event->id);
>>
>>                 return;
>> Better have this on stderr, as well?
> 
> This is more suitable for stderr, indeed.
> 
>>> @@ -278,14 +278,14 @@ int main(int argc, char **argv)
>>>       fd = open(chrdev_name, 0);
>>>       if (fd == -1) {
>>>               ret = -errno;
>>> -             fprintf(stdout, "Failed to open %s\n", chrdev_name);
>>> +             fprintf(stderr, "Failed to open %s\n", chrdev_name);
>>>               goto error_free_chrdev_name;
>>>       }
>>>
>>>       ret = ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
>>>       if (ret == -1 || event_fd == -1) {
>>>               ret = -errno;
>>> -             fprintf(stdout, "Failed to retrieve event fd\n");
>>> +             fprintf(stderr, "Failed to retrieve event fd\n");
>>>               if (close(fd) == -1)
>>>                       perror("Failed to close character device file");
>>>
>>
>> A similar borderline case as above in line 301:
>>                 ret = read(event_fd, &event, sizeof(event));
>>                 if (ret == -1) {
>>                         if (errno == EAGAIN) {
>>                                 printf("nothing available\n");
>>                                 continue;
>>
>>> @@ -311,7 +311,7 @@ int main(int argc, char **argv)
>>>               }
>>>
>>>               if (ret != sizeof(event)) {
>>> -                     printf("Reading event failed!\n");
>>> +                     fprintf(stderr, "Reading event failed!\n");
>>>                       ret = -EIO;
>>>                       break;
>>>               }
>>> diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c
>>> index 8fb3214..46dfa3f 100644
>>> --- a/tools/iio/iio_utils.c
>>> +++ b/tools/iio/iio_utils.c
>>> @@ -140,7 +140,8 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
>>>                       sysfsfp = fopen(filename, "r");
>>>                       if (sysfsfp == NULL) {
>>>                               ret = -errno;
>>> -                             printf("failed to open %s\n", filename);
>>> +                             fprintf(stderr, "failed to open %s\n",
>>> +                                     filename);
>>>                               goto error_free_filename;
>>>                       }
>>>
>>> @@ -152,7 +153,8 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
>>>                                    &padint, shift);
>>>                       if (ret < 0) {
>>>                               ret = -errno;
>>> -                             printf("failed to pass scan type description\n");
>>> +                             fprintf(stderr,
>>> +                                     "failed to pass scan type description\n");
>>>                               goto error_close_sysfsfp;
>>>                       } else if (ret != 5) {
>>>                               ret = -EIO;
>>> @@ -170,7 +172,8 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
>>>                       *is_signed = (signchar == 's');
>>>                       if (fclose(sysfsfp)) {
>>>                               ret = -errno;
>>> -                             printf("Failed to close %s\n", filename);
>>> +                             fprintf(stderr, "Failed to close %s\n",
>>> +                                     filename);
>>>                               goto error_free_filename;
>>>                       }
>>>
>>> @@ -454,7 +457,8 @@ int build_channel_array(const char *device_dir,
>>>                       sysfsfp = fopen(filename, "r");
>>>                       if (sysfsfp == NULL) {
>>>                               ret = -errno;
>>> -                             printf("failed to open %s\n", filename);
>>> +                             fprintf(stderr, "failed to open %s\n",
>>> +                                     filename);
>>>                               free(filename);
>>>                               goto error_cleanup_array;
>>>                       }
>>> @@ -581,11 +585,13 @@ int find_type_by_name(const char *name, const char *type)
>>>                       ret = sscanf(ent->d_name + strlen(type), "%d", &number);
>>>                       if (ret < 0) {
>>>                               ret = -errno;
>>> -                             printf("failed to read element number\n");
>>> +                             fprintf(stderr,
>>> +                                     "failed to read element number\n");
>>>                               goto error_close_dir;
>>>                       } else if (ret != 1) {
>>>                               ret = -EIO;
>>> -                             printf("failed to match element number\n");
>>> +                             fprintf(stderr,
>>> +                                     "failed to match element number\n");
>>>                               goto error_close_dir;
>>>                       }
>>>
>>> @@ -664,7 +670,7 @@ static int _write_sysfs_int(const char *filename, const char *basedir, int val,
>>>       sysfsfp = fopen(temp, "w");
>>>       if (sysfsfp == NULL) {
>>>               ret = -errno;
>>> -             printf("failed to open %s\n", temp);
>>> +             fprintf(stderr, "failed to open %s\n", temp);
>>>               goto error_free;
>>>       }
>>>
>>> @@ -685,7 +691,7 @@ static int _write_sysfs_int(const char *filename, const char *basedir, int val,
>>>               sysfsfp = fopen(temp, "r");
>>>               if (sysfsfp == NULL) {
>>>                       ret = -errno;
>>> -                     printf("failed to open %s\n", temp);
>>> +                     fprintf(stderr, "failed to open %s\n", temp);
>>>                       goto error_free;
>>>               }
>>>
>>> @@ -750,7 +756,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
>>>       char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
>>>
>>>       if (temp == NULL) {
>>> -             printf("Memory allocation failed\n");
>>> +             fprintf(stderr, "Memory allocation failed\n");
>>>               return -ENOMEM;
>>>       }
>>>
>>> @@ -761,7 +767,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
>>>       sysfsfp = fopen(temp, "w");
>>>       if (sysfsfp == NULL) {
>>>               ret = -errno;
>>> -             printf("Could not open %s\n", temp);
>>> +             fprintf(stderr, "Could not open %s\n", temp);
>>>               goto error_free;
>>>       }
>>>
>>> @@ -782,7 +788,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
>>>               sysfsfp = fopen(temp, "r");
>>>               if (sysfsfp == NULL) {
>>>                       ret = -errno;
>>> -                     printf("Could not open file to verify\n");
>>> +                     fprintf(stderr, "Could not open file to verify\n");
>>>                       goto error_free;
>>>               }
>>>
>>> @@ -856,7 +862,7 @@ int read_sysfs_posint(const char *filename, const char *basedir)
>>>       char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
>>>
>>>       if (temp == NULL) {
>>> -             printf("Memory allocation failed");
>>> +             fprintf(stderr, "Memory allocation failed");
>>>               return -ENOMEM;
>>>       }
>>>
>>> @@ -903,7 +909,7 @@ int read_sysfs_float(const char *filename, const char *basedir, float *val)
>>>       char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
>>>
>>>       if (temp == NULL) {
>>> -             printf("Memory allocation failed");
>>> +             fprintf(stderr, "Memory allocation failed");
>>>               return -ENOMEM;
>>>       }
>>>
>>> @@ -950,7 +956,7 @@ int read_sysfs_string(const char *filename, const char *basedir, char *str)
>>>       char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
>>>
>>>       if (temp == NULL) {
>>> -             printf("Memory allocation failed");
>>> +             fprintf(stderr, "Memory allocation failed");
>>>               return -ENOMEM;
>>>       }
>>>
>>>
>>
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