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Subject: media: rc: sir_ir: detect presence of port Author: Sean Young sean@mess.org Date: Wed Nov 8 16:19:45 2017 -0500
Without this test, sir_ir clumsy claims resources for a device which does not exist.
The 0-day kernel test robot reports the following errors (in a loop): sir_ir sir_ir.0: Trapped in interrupt genirq: Flags mismatch irq 4. 00000000 (ttyS0) vs. 00000000 (sir_ir)
When sir_ir is loaded with the default io and irq, the following happens: - sir_ir claims irq 4 - user space opens /dev/ttyS0 - in serial8250_do_startup(), some setup is done for ttyS0, which causes irq 4 to fire (in THRE test) - sir_ir does not realise it was not for it, and spins until the "trapped in interrupt" - now serial driver calls setup_irq() and fails and we get the "Flags mismatch" error.
There is no port present at 0x3e8 so simply check for the presence of a port, as suggested by Linus.
Reported-by: kbuild test robot fengguang.wu@intel.com Tested-by: Fengguang Wu fengguang.wu@intel.com Signed-off-by: Sean Young sean@mess.org Cc: stable@vger.kernel.org # 4.12+ Signed-off-by: Mauro Carvalho Chehab mchehab@s-opensource.com
drivers/media/rc/sir_ir.c | 40 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 36 insertions(+), 4 deletions(-)
---
diff --git a/drivers/media/rc/sir_ir.c b/drivers/media/rc/sir_ir.c index 76120664b700..9ee2c9196b4d 100644 --- a/drivers/media/rc/sir_ir.c +++ b/drivers/media/rc/sir_ir.c @@ -57,7 +57,7 @@ static void add_read_queue(int flag, unsigned long val); static irqreturn_t sir_interrupt(int irq, void *dev_id); static void send_space(unsigned long len); static void send_pulse(unsigned long len); -static void init_hardware(void); +static int init_hardware(void); static void drop_hardware(void); /* Initialisation */
@@ -263,11 +263,36 @@ static void send_pulse(unsigned long len) } }
-static void init_hardware(void) +static int init_hardware(void) { + u8 scratch, scratch2, scratch3; unsigned long flags;
spin_lock_irqsave(&hardware_lock, flags); + + /* + * This is a simple port existence test, borrowed from the autoconfig + * function in drivers/tty/serial/8250/8250_port.c + */ + scratch = sinp(UART_IER); + soutp(UART_IER, 0); +#ifdef __i386__ + outb(0xff, 0x080); +#endif + scratch2 = sinp(UART_IER) & 0x0f; + soutp(UART_IER, 0x0f); +#ifdef __i386__ + outb(0x00, 0x080); +#endif + scratch3 = sinp(UART_IER) & 0x0f; + soutp(UART_IER, scratch); + if (scratch2 != 0 || scratch3 != 0x0f) { + /* we fail, there's nothing here */ + spin_unlock_irqrestore(&hardware_lock, flags); + pr_err("port existence test failed, cannot continue\n"); + return -ENODEV; + } + /* reset UART */ outb(0, io + UART_MCR); outb(0, io + UART_IER); @@ -285,6 +310,8 @@ static void init_hardware(void) /* turn on UART */ outb(UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2, io + UART_MCR); spin_unlock_irqrestore(&hardware_lock, flags); + + return 0; }
static void drop_hardware(void) @@ -334,14 +361,19 @@ static int sir_ir_probe(struct platform_device *dev) pr_err("IRQ %d already in use.\n", irq); return retval; } + + retval = init_hardware(); + if (retval) { + del_timer_sync(&timerlist); + return retval; + } + pr_info("I/O port 0x%.4x, IRQ %d.\n", io, irq);
retval = devm_rc_register_device(&sir_ir_dev->dev, rcdev); if (retval < 0) return retval;
- init_hardware(); - return 0; }