Hi there,

My name is Shaobo He and I am a graduate student at University of Utah. 
I am applying a static analysis tool to the Linux device drivers and got 
an error trace of null pointer dereference in 
drivers/input/touchscreen/ad7879-spi.c staring from 
`ad7879_spi_multi_read`: it calls `ad7879_spi_xfer` with the argument 
`tx_buf` being NULL, which gets dereferenced at line 52 given the 
argument `count` being 1. As you can see, the error trace is only 
plausible since it depends on certain conditions. To be more specific, 
is it possible for the count argument to be 1. Therefore, I was 
wondering if you could help me confirm it since you are one of the 
authors of this driver.

Thanks for your time. I am looking forward to your reply.

Best,
Shaobo