Conversion of old init_timer in new linux kernel - c

Question

I am trying to build a SDK driver (with no documentation or support from the manufacturer). The original driver uses init_timer() and passes in a pointer to the timer_list structure. And it uses the 'data' element. Now I know that some of the timer functions are deprecated in the newer Linux kernels. Currently I am using kernel version 4.15.
What is the best way to access the 'data' element?
Current function looks like this -
OS_RESULT OS_TimerCreate(OS_DRV_CONTEXT* aContext, OS_TIMER* aTimer, OS_UINT32 aPeriodic, OS_TIMER_FNC aFunction,
OS_VOID* aData, OS_UINT32 aPeriod)
{
struct timer_list* lTimer = (struct timer_list*) aTimer->Space;
unsigned long lJiffies = jiffies;
unsigned long lPeriod = msecs_to_jiffies(aPeriod);
OS_UNREFERENCED_PARAMETER(aContext);
OS_ASSERT( OS_TIMER_SIZE >= sizeof(timer_list));
init_timer(lTimer);
lTimer->expires = lJiffies + lPeriod;
lTimer->data = (unsigned long) aTimer;
aTimer->Function = aFunction;
aTimer->Data = aData;
aTimer->Period = lPeriod;
if (aPeriodic)
{
lTimer->function = OS_TimerPeriodicInternalFunc;
}
else
{
lTimer->function = OS_TimerInternalFunc;
}
add_timer(lTimer);
return OS_RESULT_OK;
}
Declaration for reference -
typedef struct
{
OS_UINT8 Space[OS_TIMER_SIZE];
OS_TIMER_FNC Function;
OS_VOID* Data;
OS_UINT32 Period;
} OS_TIMER;
OS_DECL_EXTERN OS_RESULT OS_TimerCreate(OS_DRV_CONTEXT* aContext, OS_TIMER* aTimer, OS_UINT32 aPeriodic, OS_TIMER_FNC aFunction, OS_VOID* aData, OS_UINT32 aPeriod /* ms */);
Any help will be appreciated.

Answer 1

You first need to change the member that stores the struct timer_list to be of the correct type instead of using an array of bytes:
typedef struct
{
struct timer_list Timer;
OS_TIMER_FNC Function;
OS_VOID* Data;
OS_UINT32 Period;
} OS_TIMER;
(and lTimer is just set to &aTimer->Timer).
In the old code the data member is just set to a pointer to the OS_TIMER structure that contains the timer. In the new code, the callback can instead get this pointer using the from_timer macro, eg if in the old callback you had this:
OS_TIMER *aTimer = lTimer->data;
then in the new code you would instead have:
OS_TIMER *aTimer = from_timer(aTimer, lTimer, Timer);
(where the last parameter Timer is the name of the struct timer_list field in OS_TIMER).