[yocto] [meta-raspberrypi][PATCH v6 3/4] linux-raspberrypi-base.bbclass: support for .dtbo files for dtb overlays

[Herve Jourdain]

Hi François,

Actually, I tried to use a -overlay.dtb as a device tree overlay with the 4.4.9, and it didn't load it...
If you don't use the tools dedicated to debug device trees (like vcdbg), there is no error message nor complaint, but the device tree is not loaded. Only when I used vcdbg did I see it complained that it could not find the .dtbo file.
I'm not sure if the loader has changed since then, but if it has not then you probably need to impose .dtbo for kernels > 4.4.6. Or issue an error if the KERNEL_DEVICETREE variable is not consistent with the kernel version...

The current behaviour is following some remark/proposal from Andrei - the very first proposal had different versions of KERNEL_DEVICETREE, depending on the kernel version actually.
But I agree with Andrei that it would be easier to just maintain one set of default values for the KERNEL_DEVICETREE.
One thing I didn't consider is the override of that variable, maybe a warning message could be added if we have to change the -overlay.dtb into .dtbo.
But we should probably do the change to 'dtbo regardless, because it's very likely it would not load properly later, with no message except with vcdbg...

Would that solution be OK with you?

Andrei, do you have any comment on this?

Herve

> Le 25 juil. 2016 à 10:45, Francois Muller <forlorn18 at gmail.com> a écrit :
> 
> Hi Hervé,
> 
> Thank you for giving us up and running .dtbo overlays functionality through this patch, it is running fine for me.
> 
> Nevertheless, I have a concern about the processing applied to overlay filenames.
> 
> According to this post https://www.raspberrypi.org/forums/viewtopic.php?f=107&t=139732, '-overlay.dtb' suffixes have been superseded by '.dtbo' suffix to reflect an improvement in overlay functionalities and thus overlay binary format (or simply content, I don't know).
> Moreover, changing the suffix gives a chance for older and newer overlay formats to coexist in a boot folder.
> 
> So, I'm not very fond of a build system changing the inputs I give to it (i.e. KERNEL_DEVICETREE) depending on another input from my side (kernel version) without at least notifying me the change occurred.
> I would highly prefer a bbwarn (or should it even fail?) if the requested overlay filenames don't suit the kernel version being chosen (btw device trees are theoretically aimed to be kernel version and even OS independent as it should only contain pure hardware platform description).
> I understand and appreciate the intention of offering a kind of compatibility for kernels prior to 4.4.6 but I don't think it's needed here. 
> 
> If KERNEL_DEVICETREE isn't empty for kernels prior to 3.18 => let's disable device trees (or simply remove this test, this layer doesn't provide any)
> If KERNEL_DEVICETREE asks for -overlay.dtb and kernel >= 3.18 => let's compile it, it has been requested
> If KERNEL_DEVICETREE asks for .dtbo and kernel < 4.4.6 => let's fail with a comprehensive message (these kernels even don't know what a .dtbo file is!)
> If KERNEL_DEVICETREE asks for -overlay.dtb and/or .dtbo and kernel >= 4.4.6 => let's compile it, it has been requested
> 
> The tough thing will be to keep consistency between KERNEL_DEVICETREE content and kernel version to build.
> So as long as 4.1 is the layer's kernel preferred version, KERNEL_DEVICETREE should only contain '-overlay.dtb' overlays, along with the next to be used KERNEL_DEVICETREE variable (containing .dtbo) that is commented out.
> As soon as 4.4 is chosen, let's default to .dtbo overlays and comment out KERNEL_DEVICETREE variable containing '-overlay.dtb' overlays.
> 
> What do you think about this behavior ?
> 
> As side notes, you may use some existing utility function to compare software versions like bb.utils.vercmp_string_op and overlays filtering may be done in a single pass : I've attached a proposal.
> 
> BR,
> François
> 
>> Le jeudi 21 juillet 2016 à 06:00 +0800, Herve Jourdain a écrit :
>> Kernel 4.4.6+ on RaspberryPi support .dtbo files for overlays, instead of .dtb.
>> Add support for both variants of overlays ("-overlay.dtb" and ".dtbo")
>> Change which variant needs to be supported based on the kernel version
>> 
>> CAUTION: when called from IMAGE_CMD_rpi-sdimg, 'TMPDIR' is not set, causing 'STAGING_KERNEL_BUILDDIR' to not be expanded, causing get_kernelversion_file() to fail!
>> To avoid this problem, get_dts() and split_overlays() MUST be called with the kernel version parameter set, when called from IMAGE_CMD_rpi-sdimg!
>> 
>> Signed-off-by: Herve Jourdain <herve.jourdain at neuf.fr>
>> ---
>>  classes/linux-raspberrypi-base.bbclass | 19 ++++++++++++-------
>>  1 file changed, 12 insertions(+), 7 deletions(-)
>> 
>> diff --git a/classes/linux-raspberrypi-base.bbclass b/classes/linux-raspberrypi-base.bbclass
>> index 40beef1..930fc44 100644
>> --- a/classes/linux-raspberrypi-base.bbclass
>> +++ b/classes/linux-raspberrypi-base.bbclass
>> @@ -1,7 +1,8 @@
>>  inherit linux-kernel-base
>>  
>> -
>>  def get_dts(d, ver):
>> +    import re
>> +
>>      staging_dir = d.getVar("STAGING_KERNEL_BUILDDIR", True)
>>      dts = d.getVar("KERNEL_DEVICETREE", True)
>>  
>> @@ -20,20 +21,24 @@ def get_dts(d, ver):
>>  
>>      # Always turn off device tree support for kernel's < 3.18
>>      try:
>> -        if int(min_ver[0]) <= 3:
>> -            if int(min_ver[1]) < 18:
>> -                dts = ""
>> +        if int(min_ver[0]) >= 4:
>> +            if (int(min_ver[1]) < 4) or (int(min_ver[1]) == 4 and int(min_ver[2]) < 6):
>> +                dts = ' '.join([(re.sub(r'(.*)\.dtbo$', r'\1-overlay.dtb', x)) for x in dts.split()])
>> +        elif int(min_ver[1]) < 18:
>> +            dts = ""
>>      except IndexError:
>>          min_ver = None
>>  
>>      return dts
>>  
>>  
>> -def split_overlays(d, out):
>> -    dts = get_dts(d, None)
>> +def split_overlays(d, ver, out):
>> +    dts = get_dts(d, ver)
>>      if out:
>>          overlays = oe.utils.str_filter_out('\S+\-overlay\.dtb$', dts, d)
>> +        overlays = oe.utils.str_filter_out('\S+\.dtbo$', overlays, d)
>>      else:
>> -        overlays = oe.utils.str_filter('\S+\-overlay\.dtb$', dts, d)
>> +        overlays = oe.utils.str_filter('\S+\-overlay\.dtb$', dts, d) + \
>> +                   " " + oe.utils.str_filter('\S+\.dtbo$', dts, d)
>>  
>>      return overlays
>> -- 
>> 2.7.4
>> 
> <linux-raspberrypi-base.bbclass>
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