[QUERY] wic running in buildchroot-target

[chombourger@gmail.com]

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Hello all,

I am continuing my journey on the MIPS architecture.
I wanted to add wks files for my MIPS target (Creator Ci40) and 
do_wic_image failed:

INFO: Creating image(s)...

-rw-r--r-- 1 root root 697932185 Jun 18 13:34 
/tmp/development-image-mel-omni-img-creator-ci40.wic/tmp.wic.n3m8x3xo/rootfs_platforma.1.ext4
Unsupported ioctl: cmd=0x0002
Traceback (most recent call last):
  File "/home/chombourger/Projects/isar/scripts/lib/wic/filemap.py", line 
40, in get_block_size
    binary_data = fcntl.ioctl(file_obj, 2, struct.pack('I', 0))
OSError: [Errno 89] Function not implemented

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/chombourger/Projects/isar/scripts/lib/wic/filemap.py", line 
103, in __init__
    self.block_size = get_block_size(self._f_image)
  File "/home/chombourger/Projects/isar/scripts/lib/wic/filemap.py", line 
42, in get_block_size
    raise IOError("Unable to determine block size")
OSError: Unable to determine block size

wic appears to be running from buildchroot-target and therefore under 
qemu-<arch>-static
evidently mips does not implement the FIGETBSZ ioctl

My options would be:

(1) check if a more recent version of qemu does implement this ioctl
(2) add support for this ioctl in qemu-user
(3) work-around it in wic with something like:

diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 080668e..1ce3ace 100644
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -40,8 +40,13 @@ def get_block_size(file_obj):
 
     # Get the block size of the host file-system for the image file by 
calling
     # the FIGETBSZ ioctl (number 2).
-    binary_data = ioctl(file_obj, 2, struct.pack('I', 0))
-    return struct.unpack('I', binary_data)[0]
+    try:
+        binary_data = ioctl(file_obj, 2, struct.pack('I', 0))
+        return struct.unpack('I', binary_data)[0]
+    except OSError as err:
+        if err.errno == os.errno.ENOSYS:
+            return 4096
+        raise err
 
 class ErrorNotSupp(Exception):
     """

Ok.

But why are we running wic in buildchroot-target. Comments I have seen in 
the code only say that it is a prerequisite but do not say why (I should 
probably check git logs as well)
I wonder if it should run in buildchroot-host context instead (so we still 
use a host environment we control) but avoid the overhead of qemu emulation 
for DISTRO_ARCH != amd64

What are your thoughts?

Cedric


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