Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Does anyboy use "struct semaphore" and down(struct semaphore

Hello everyone,

I use the latest version of nios2-linux(nios2-linux-20090730),when I test the driver nios2-linux/linux-2.6/drivers/char/altera_pio_button.c,I found that the function down(struct semaphore *) never return.I think it's a serious problem,drivers can not work without semphare,wake_up(wait_queue_head_t *) seems not work too,I can not find their definitions,so I don't know why, could anybody help me.

Thank you

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Did I descript it clearly?The test process is las follows:

    1.fd=open("/dev/pio_button",O_RDONLY);

    2.ret=read(fd,&key_value,sizeof(key_value));

    I had not press any button,so it blocked itself and called schedule(),then I pressed a button,so pio_button_isr() was called,in the end it schedule work_queue,(here the handle is button_handle_event()),in button_handle_event(),so down(&dev->mutex) appears,it never return!That's the problem!

    I don't think there are any dead lock!

    I have see some source code(NIOSSerial.c,altspi.c ),they don't use down()!
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    The pio port base should remapped to uncached. Try# define PIO_BUTTON_BASE (na_button_pio | 0x80000000)

    I've never used that driver myself. It is just a personal taste. I prefer using gpio and input subsystem which supports polling instead of interrupt driven. Please see the example at linux-2.6/drivers/input/mouse/gpio_mouse.c .

    http://www.nioswiki.com/gpio (http://www.nioswiki.com/gpio)

    - Hippo