linux-kernel - Re: [PATCH ]:Staging: hv: Allocate the vmbus irq dynamically

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Message-ID: <20110215155954.GA32313@suse.de>
Date:	Tue, 15 Feb 2011 07:59:54 -0800
From:	Greg KH <gregkh@...e.de>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
	virtualization@...ts.osdl.org,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Hank Janssen <hjanssen@...rosoft.com>
Subject: Re: [PATCH ]:Staging: hv: Allocate the vmbus irq dynamically

On Tue, Feb 15, 2011 at 07:15:37AM -0800, K. Y. Srinivasan wrote:
> 
> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> Signed-off-by: Hank Janssen <hjanssen@...rosoft.com>
> 
> ---
>  drivers/staging/hv/vmbus_drv.c |   49 +++++++++++++++++++++++++++------------
>  1 files changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/staging/hv/vmbus_drv.c b/drivers/staging/hv/vmbus_drv.c
> index 459c707..f279e6a 100644
> --- a/drivers/staging/hv/vmbus_drv.c
> +++ b/drivers/staging/hv/vmbus_drv.c
> @@ -36,9 +36,7 @@
>  #include "vmbus_private.h"
>  
>  
> -/* FIXME! We need to do this dynamically for PIC and APIC system */
> -#define VMBUS_IRQ		0x5
> -#define VMBUS_IRQ_VECTOR	IRQ5_VECTOR
> +static int vmbus_irq;
>  
>  /* Main vmbus driver data structure */
>  struct vmbus_driver_context {
> @@ -57,6 +55,25 @@ struct vmbus_driver_context {
>  	struct vm_device device_ctx;
>  };
>  
> +/*
> + * Find an un-used IRQ that the VMBUS can use. If none is available; return -1.
> + */
> +
> +static int vmbus_get_irq(void)

No extra blank line between function comment and function.

> +{
> +	unsigned int avail_irq_mask;
> +	int irq = -1;
> +	/*

Put an extra blank line after your variables please.

> +	 * Pick the first unused interrupt. HyperV can
> +	 * interrupt us on any interrupt line we specify.
> +	 */
> +	avail_irq_mask = probe_irq_on();
> +	if (avail_irq_mask != 0)
> +		irq = ffs(avail_irq_mask);
> +	probe_irq_off(avail_irq_mask);
> +	return irq;
> +}
> +
>  static int vmbus_match(struct device *device, struct device_driver *driver);
>  static int vmbus_probe(struct device *device);
>  static int vmbus_remove(struct device *device);
> @@ -80,7 +97,6 @@ EXPORT_SYMBOL(vmbus_loglevel);
>  	/* (ALL_MODULES << 16 | DEBUG_LVL_ENTEREXIT); */
>  	/* (((VMBUS | VMBUS_DRV)<<16) | DEBUG_LVL_ENTEREXIT); */
>  
> -static int vmbus_irq = VMBUS_IRQ;
>  
>  /* Set up per device attributes in /sys/bus/vmbus/devices/<bus device> */
>  static struct device_attribute vmbus_device_attrs[] = {
> @@ -466,7 +482,7 @@ static int vmbus_bus_init(void)
>  	struct hv_driver *driver = &vmbus_drv.drv_obj;
>  	struct vm_device *dev_ctx = &vmbus_drv.device_ctx;
>  	int ret;
> -	unsigned int vector;
> +	unsigned int vector, prev_irq = ~0;
>  
>  	DPRINT_INFO(VMBUS, "+++++++ HV Driver version = %s +++++++",
>  		    HV_DRV_VERSION);
> @@ -518,19 +534,23 @@ static int vmbus_bus_init(void)
>  	}
>  
>  	/* Get the interrupt resource */
> -	ret = request_irq(vmbus_irq, vmbus_isr, IRQF_SAMPLE_RANDOM,
> -			  driver->name, NULL);
> -
> -	if (ret != 0) {
> -		DPRINT_ERR(VMBUS_DRV, "ERROR - Unable to request IRQ %d",
> -			   vmbus_irq);
> -
> +get_irq_again:
> +	vmbus_irq = vmbus_get_irq();
> +	if ((vmbus_irq < 0) || (prev_irq == vmbus_irq)) {
> +		printk(KERN_WARNING "VMBUS_DRV: Failed to allocate IRQ\n");
>  		bus_unregister(&vmbus_drv_ctx->bus);
> -
>  		ret = -1;

Please provide a "real" error code.

>  		goto cleanup;
>  	}
> -	vector = VMBUS_IRQ_VECTOR;
> +	prev_irq = vmbus_irq;
> +
> +	ret = request_irq(vmbus_irq, vmbus_isr, IRQF_SAMPLE_RANDOM,
> +			  driver->name, NULL);
> +
> +	if (ret != 0)
> +		goto get_irq_again;

You just set up the potential for an endless loop.  You almost _never_
want to goto backwards in a function.  Please don't do this.

> +
> +	vector = IRQ0_VECTOR + vmbus_irq;

What's this for?

>  	DPRINT_INFO(VMBUS_DRV, "irq 0x%x vector 0x%x", vmbus_irq, vector);

And why are you still printing this out for the whole world to see?

thanks,

greg k-h
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