Moving from FreeBSD7 to FreeBSD8 (cdev, minor, dev2unit)

[Dmitry Krivenok]

Hello Hackers,

I'm working on porting some kernel modules written for FreeBSD7 to FreeBSD8.
Some of these modules contain the following code:

struct cdev *dev;
...
int dev_num = minor(dev);

This code doesn't compile on FreeBSD8.
I found that in FreeBSD7 minor() was defined as follows:

  515 int
  516 minor(struct cdev *x)
  517 {
  518         if (x == NULL)
  519                 return NODEV;
  520         return(x->si_drv0 & MAXMINOR);
  521 }

where MAXMINOR was defined as

  236 #define MAXMINOR        0xffff00ffU

But in FreeBSD8 minor() is defined as macro that takes integer as a parameter:

  323 #define minor(x)        ((int)((x)&0xffff00ff))         /* minor number */

I also found that FreeBSD8 provides dev2unit macro:

  276 #define dev2unit(d)     ((d)->si_drv0)

It looks like dev2unit is exactly what I need to fix compilation issue.
I changed the code of all modules as follows:

- int dev_num = minor(dev);
+ int dev_num = minor(dev2unit(dev));

and now it compiles and works well.

Is this the proper way of solving the problem?

Thanks in advance!

--
Sincerely yours, Dmitry V. Krivenok
e-mail: krivenok.dmitry at gmail.com
skype: krivenok_dmitry
jabber: krivenok_dmitry at jabber.ru
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