[fmela]

In the device_read function,

  len — ;

should be

  len --;

[megous]

Probably a CMS thing. printk is probably also discouraged, these days. pr_warn/info/..() or dev_warn/info/err...() should be used.

Also for anyone writing kernel code, this is indispensable: http://elixir.free-electrons.com/linux/latest/source

[uep]

It doesn't exactly apply here since the author doesn't seem to be allocating resources dynamically, but another thing that's "newer" and less widely used are the devm_ family of functions.

Nowadays, lots of code could be using devm_kmalloc, devm_ioremap, etc which will release the resources automatically when the driver detaches from the device.

[dpedu]

Copy-paste trap!