iio_attr infinite loop when writing to DAC

[SJ-Innovation]

Issuing an iio_attr command to write to the value of the DAC changes the value of the DAC successfully but hangs as it does so. The DAC updates successfully (verified by scoping output frequency), and can be read/written directly by devmem to its respective absolute address.

I suspect this may be due to the ad5660_mp driver added in this patch, which has some... Non-conformities... In how it uses IIO.
I have modified the driver to fix the below notes, and the DAC updates successfully. Happy to make a PR if requested.

1. show/store functions are referenced by attributes which will cause EINVAL. Better to just use nullptrs so IIO itself generates the error, by setting more appropriate permissions on the unrequired store/show references.

2. store function return value is incorrect, as are polarities of EINVAL throughout.

[yxb2004]

可以请问一下你的固件版本是多少吗，我用的是0.34版本，输入iio_attr -d命令根本查不到ad5660_mp这个iio设备

[SJ-Innovation]

I use modified 0.39, check the commit history.

ad5660_mp support was added in the buildup to 0.38. Upgrade your FW

[yxb2004]

您好再次请问一下，升级固件使用的是plutosdr的固件升级包吗

[SJ-Innovation]

1. I dont work for Microphase so dont expect support from me
2. You're hijacking the issue with unrelated questions. Stop. If you have problems create (and close when solved) a specific issue for it.
3. You cant use the PlutoSDR upgrader as this isnt a plutosdr, uses different internal configs etc. The pluto upgrader will download a PlutoSDR specific version which wont work on E200s. Follow the instructions in the readme, write the firmware files directly to the SD card & the E200 will boot from them.