Hello to all. I'm working on writing a tool that will control a piece of
hardware using ioctl's on its device node. Specifically, I'm trying to
configure and tune a DVB-S receiver on Linux.
Just for starters, I want to try opening the frontend and setting the LNB
voltage. An example in C:
###
/* all the normal #include's omitted */
#include <linux/dvb/frontend.h>
fd = open("/dev/dvb/adapter1/frontend0", O_RDWR)
r = ioctl (fd, FE_SET_VOLTAGE, SEC_VOLTAGE_18);
if (r == -1)
perror ("ioctl FE_SET_VOLTAGE");
###
The relevant definitions in linux/dvb/frontend.h:
###
typedef enum fe_sec_voltage {
SEC_VOLTAGE_13,
SEC_VOLTAGE_18,
SEC_VOLTAGE_OFF
} fe_sec_voltage_t;
...
#define FE_SET_VOLTAGE _IO('o', 67) /* fe_sec_voltage_t */
###
So, I wrote the following in Python:
###
import fcntl
fe_set_voltage = 67
sec_voltage_13 = 0
sec_voltage_18 = 1
sec_voltage_off = 2
fd = open("/dev/dvb/adapter1/frontend0", "wb")
fcntl.ioctl(fd, fe_set_voltage, sec_voltage_18)
###
This fails with "IOError: [Errno 95] Operation not supported".
Considering I'm not too good with C, and know absolutely /nothing/ about device
drivers or kernel code, I'm certain I'm missing something simple and obvious.
Anyone want to set me straight?
Thanks,
-Joe
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