Re: [PATCH] i2c driver fixes for 2.6.0-test5

[Greg KH <greg@kroah.com>]

On Tue, Sep 23, 2003 at 05:22:58PM +0100, Christoph Hellwig wrote:
> On Tue, Sep 23, 2003 at 09:19:29AM -0700, Greg KH wrote:
> > Ok, from my reading of this horrible chunk of code it does the
> > following:
> > 	- if this is a isa based controller, then we check the region
> > 	  that is to be used.
> > 	- If it is already in use by someone else, then we skip it, and
> > 	  move on to the next address.
> > 	- If it is not in use, then we pass the address down to the chip
> > 	  driver and let it try to find the chip at this address (it
> > 	  will do the reserving of the address space on its own.)
> > 
> > So basically, check_region is pretty valid here, as we are trying to see
> > if something else is already at this address, to try to prevent i2c
> > drivers from stomping on each other.  I replaced this with a
> > request_region()/release_region() pair to get rid of the compiler
> > warning.
> > 
> > Is this your understanding too?  Or do you think we should just get rid
> > of the request_region() check here all together?
> 
> Yes, either we should get rid of it or move claiming the address to
> the i2c midlayer (not sure whether that's a good idea).  But an
> opencoded check_region doesn't make any more sense than an explicit
> one.  And you're also looking at the pointer it returned after it's
> already invalid again..

Heh, good point.  Ok, I dug out a box that uses a isa i2c adapter and
tested the patch below.  As the chip drivers are using request_region
properly, taking this check out of i2c-sensor.c makes sense.

thanks,

greg k-h


diff -Nru a/drivers/i2c/i2c-sensor.c b/drivers/i2c/i2c-sensor.c
--- a/drivers/i2c/i2c-sensor.c	Tue Sep 23 12:03:13 2003
+++ b/drivers/i2c/i2c-sensor.c	Tue Sep 23 12:03:13 2003
@@ -50,10 +50,7 @@
 		return -1;
 
 	for (addr = 0x00; addr <= (is_isa ? 0xffff : 0x7f); addr++) {
-		void *region_used = request_region(addr, 1, "foo");
-		release_region(addr, 1);
-		if ((is_isa && (region_used == NULL)) ||
-		    (!is_isa && i2c_check_addr(adapter, addr)))
+		if (!is_isa && i2c_check_addr(adapter, addr))
 			continue;
 
 		/* If it is in one of the force entries, we don't do any