Re: [Xenomai-help] RTDM interrupt questions

[Jan Kiszka <jan.kiszka@domain.hid>]

Steven Kauffmann wrote:
> On Nov 5, 2007 10:17 AM, Jeroen Van den Keybus <
> jeroen.vandenkeybus@domain.hid> wrote:
> 
>>  Ok, dev->irq gives number 22 and interrupt is working.
>>>
>>>
>>>>> The result is 10, but the result of lspci -v is:
>> As far as I know, the IRQ value field in the PCI config area is rather a
>> scratch pad memory, and intended to be set correctly by the BIOS after PCI
>> device enumeration. When interrupts are changed from the BIOS
>> defaults during e.g. ACPI config, no one seems to care about this value
>> anymore. As pointed out earlier, use dev->irq, which is always correct.
>>
>>
>>>
>> Is there not something like a signal I can set in the interrupt routine of
>> the driver. The user space application have to wait its execution until the
>> signal is set?
>>
>> Yes, you could use the following code:
>>
>> #include <rtdm/rtdm_driver.h>
>>
>> static rtdm_event_t evt;
>>
>> static int realtime_intr(rtdm_irq_t *irq_context)
>> {
>>     acknowledge_irq_on_fpga_card();
>>     rtdm_event_signal(&evt);
>> }
>>
>> static int realtime_read(struct rtdm_dev_context *context,
>> rtdm_user_info_t *user_info, void *buf, size_t nbyte)
>> {
>>     // ...
>>     err = rtdm_event_wait(&evt);
>>     get_data_from_fpga_card();
>>     // ...
>> }
>>
>> static int realtime_open()
>> {
>>     // ...
>>     evt = rtdm_evt_init(&evt);
>>     enable_irq_from_fpga_card();
>>     // ...
>> }
>>
>> This is assuming use of the RTDM. You can do the rtdm_event_wait from a
>> user task equally, I would think.
>>
> 
> The RTDM code is compiled as a kernel module, so I can't use the
> rtdm_event_wait function in the driver. That part should be in the user

Why do you think you cannot use that service? You can.

> space application which is a real-time task. The API documentation says that
> the rtdm_event_wait function can be called from an user-space task(RT). How

The documentation _means_ (but doesn't state it clearly enough, I know)
that you can call this service in the _context_ of a user space RT task
that called into your driver.

> do I have to use it in an user-space task(RT) if rtdm_event_wait is not
> defined in rtdm.h?

The applications invokes some driver services, e.g. ioctl or read, and
your driver can then block the task by calling rtdm_event_wait in the
kernel on behalf of the task, that's the idea.

> 
> For the moment I have the kernel module(driver that communicates with the
> FPGA card), 1 user space applications(real-time tasks). For example the FPGA
> implements a multiplier. The user space task sends 2 values to the driver,
> after that it should wait (rtdm_event_wait if it is possible). When the
> multiplier on the FPGA is done, it generates an interrupt. The RTDM driver
> receives this interrupt and sends a signal to the user space task that it
> can stop waiting and read the result of the multiplying.
> 
> I hope that this makes it easier to understand my problem.

Yep, and I hope the explanations above helped to clarify the situation.
If not, just tell us what remains unclear.

Jan

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