iio: generic_buffer: be helpful about enabling channels

Currently if generic_buffer is invoked without first enabling any
channels in scan_elements/*_en, it will fail unable to enable the
buffer because bytes_per_datum inside the kernel will be zero if
no channels are available.

It is implied that the user of the program should enable channels
manually or with a script before executing generic_buffer.

Be more helpful by stopping execution if no enabled channels can
be found, and print a helptext that will tell you what is wrong
and what needs to be done.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
index 9f7b85bf6ada..01c4f67801e0 100644
--- a/tools/iio/generic_buffer.c
+++ b/tools/iio/generic_buffer.c
@@ -328,6 +328,15 @@ int main(int argc, char **argv)
                         "diag %s\n", dev_dir_name);
                 goto error_free_triggername;
         }
+        if (!num_channels) {
+                fprintf(stderr,
+                        "No channels are enabled, we have nothing to scan.\n");
+                fprintf(stderr, "Enable channels manually in "
+                        FORMAT_SCAN_ELEMENTS_DIR
+                        "/*_en and try again.\n", dev_dir_name);
+                ret = -ENOENT;
+                goto error_free_triggername;
+        }
 
         /*
          * Construct the directory name for the associated buffer.