Parallel port write through character file fails occasionally with "write error: Operation not permitted"

[spinlockirqsave]

Parallel port write fails occasionally, succeeds always on next write.

root@debian1:/ldd3-samples/short# echo -n "0" > /dev/short0 bash: echo: write error: Operation not permitted root@debian1:/ldd3-samples/short# echo -n "0" > /dev/short0 root@debian1:/ldd3-samples/short# echo -n "0" > /dev/short0

[ 3749.614133] short: init, req region OK [ 3749.614528] short: init registered irq [7] [ 3749.614534] short: init, irq [7] base [888] use_mem [0] major [250] probe [0] share [0] [ 3774.100000] short: cleanup [ 3840.883497] short: init, req region OK [ 3840.883623] short: init registered irq [7] [ 3840.883625] short: init, irq [7] base [53248] use_mem [0] major [250] probe [0] share [0] [ 4145.343071] short: do_short_write value error [ 4149.304409] short: write, val [1], port [53248] [ 4165.372757] short: do_short_write value error [ 4167.002722] short: write, val [2], port [53248]

Fix if (kstrtouint(kbuf, 10, &val) != 0 || val > 255) {

•  printk("short: do_short_write value error\n");
  

•  return -1;
  

• }

[spinlockirqsave]

PR will be opened