From: Jiri Slaby Test if base addr is non-null in ISR to prove the card has been correctly initialized. This is needed for DEBUG_SHIRQ for example. Signed-off-by: Jiri Slaby Signed-off-by: Andrew Morton --- drivers/char/cyclades.c | 4 ++++ 1 file changed, 4 insertions(+) diff -puN drivers/char/cyclades.c~char-cyclades-allow-debug_shirq drivers/char/cyclades.c --- a/drivers/char/cyclades.c~char-cyclades-allow-debug_shirq +++ a/drivers/char/cyclades.c @@ -1444,6 +1444,10 @@ static irqreturn_t cyy_interrupt(int irq card_base_addr = cinfo->base_addr; index = cinfo->bus_index; + /* card was not initialized yet (e.g. DEBUG_SHIRQ) */ + if (unlikely(card_base_addr == NULL)) + return IRQ_HANDLED; + /* This loop checks all chips in the card. Make a note whenever _any_ chip had some work to do, as this is considered an indication that there will be more to do. Only when no chip _