Re: [PATCH] mpc i2c driver, compare to NO_IRQ instead of zero

[Jean Delvare <khali@linux-fr.org>]

Hi Jon,

On Tue, 19 Feb 2008 17:42:21 +0100, Jean Delvare wrote:
> On Mon, 21 Jan 2008 15:07:40 -0500, Jon Smirl wrote:
> > Alter the mpc i2c driver to use the NO_IRQ symbol instead of
> > the constant zero when checking for valid interrupts. NO_IRQ=-1
> > on ppc and NO_IRQ=0 on powerpc so the checks against zero are
> > not correct.
> 
> Using NO_IRQ sounds good, just one question:
> 
> > 
> > Signed-off-by: Jon Smirl <jonsmirl@gmail.com>
> > ---
> > 
> >  drivers/i2c/busses/i2c-mpc.c |   10 +++++-----
> >  1 files changed, 5 insertions(+), 5 deletions(-)
> > 
> > 
> > diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
> > index bbe787b..d20959d 100644
> > --- a/drivers/i2c/busses/i2c-mpc.c
> > +++ b/drivers/i2c/busses/i2c-mpc.c
> > @@ -99,7 +99,7 @@ static int i2c_wait(struct mpc_i2c *i2c, unsigned timeout, int writing)
> >  	u32 x;
> >  	int result = 0;
> >  
> > -	if (i2c->irq == 0)
> > +	if (i2c->irq == NO_IRQ)
> >  	{
> >  		while (!(readb(i2c->base + MPC_I2C_SR) & CSR_MIF)) {
> >  			schedule();
> > @@ -329,7 +329,7 @@ static int fsl_i2c_probe(struct platform_device *pdev)
> >  		return -ENOMEM;
> >  
> >  	i2c->irq = platform_get_irq(pdev, 0);
> > -	if (i2c->irq < 0) {
> > +	if (i2c->irq < NO_IRQ) {
> 
> I am skeptical about this one. Can platform_get_irq() really return
> NO_IRQ? I thought that the IRQ resource would be plain missing if the
> device has no IRQ, so I would expect:
> 
>  	i2c->irq = platform_get_irq(pdev, 0);
> 	if (i2c->irq < 0)
> 		i2c->irq = NO_IRQ; /* Use polling */
> 
> Testing against NO_IRQ suggests that devices with no IRQ would still
> have an IRQ resource defined and explicitly set to NO_IRQ. Sounds weird
> to me. Can you please clarify this point?
> 
> For what it's worth, no other kernel driver checks for irq < NO_IRQ.
> They all check for irq < 0 after calling platform_get_irq().
> 
> >  		result = -ENXIO;
> >  		goto fail_get_irq;
> >  	}
> > @@ -344,7 +344,7 @@ static int fsl_i2c_probe(struct platform_device *pdev)
> >  		goto fail_map;
> >  	}
> >  
> > -	if (i2c->irq != 0)
> > +	if (i2c->irq != NO_IRQ)
> >  		if ((result = request_irq(i2c->irq, mpc_i2c_isr,
> >  					  IRQF_SHARED, "i2c-mpc", i2c)) < 0) {
> >  			printk(KERN_ERR
> > @@ -367,7 +367,7 @@ static int fsl_i2c_probe(struct platform_device *pdev)
> >  	return result;
> >  
> >        fail_add:
> > -	if (i2c->irq != 0)
> > +	if (i2c->irq != NO_IRQ)
> >  		free_irq(i2c->irq, i2c);
> >        fail_irq:
> >  	iounmap(i2c->base);
> > @@ -384,7 +384,7 @@ static int fsl_i2c_remove(struct platform_device *pdev)
> >  	i2c_del_adapter(&i2c->adap);
> >  	platform_set_drvdata(pdev, NULL);
> >  
> > -	if (i2c->irq != 0)
> > +	if (i2c->irq != NO_IRQ)
> >  		free_irq(i2c->irq, i2c);
> >  
> >  	iounmap(i2c->base);
> 
> The rest looks good.

Any news about this patch? I had a question above which is left
unanswered. If you want this patch merged in 2.6.26 you'll have to be
quick.

-- 
Jean Delvare