[PATCH] mm-modem-helpers-qmi: avoid SIGSEGV with mmcli --set-current-bands

[Reinhard Speyerer]

On Wed, Aug 21, 2019 at 07:15:28AM +1000, Nick wrote:
> Hi Reinhard,
> 
> Yes you are right, I double checked the supported bands afterwards and 32 is not one of them.  The issue was that mmcli had reported eutran-32 as a supported band.  I also know that normally both mmcli and qmicli  would safely error out with an unsupported band message.  So it was a size issue causing the bitwise operations to get messed up?  Would LTE bands 65+ need a bigger type?
> 

Hi Nicholas,

please refer to this thread
<https://stackoverflow.com/questions/29538935/why-does-unsigned-char0x80-24-get-sign-extended-to-0xffffffff80000000-64?noredirect=1&lq=1>
for an explanation of the observed behaviour.

QMI uses additional TLVs for LTE bands > 64. Please refer to
data/{qmi-service-dms.json,qmi-service-nas.json} in the libqmi sources
for details.

Regards,
Reinhard