Re: 32bit dev_t

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <UTC200301242204.h0OM4jU09451.aeb@smtp.cwi.nl>
By author:    Andries.Brouwer@cwi.nl
In newsgroup: linux.dev.kernel
> 
> The main point to decide would be the external dev_t format.
> Of course the format must be compatible with existing filesystems
> and binaries. For example,
> 
> #define MAJOR(dev)      ((unsigned int)(((dev) & 0xffff0000) \
> 	? ((dev) >> 16) & 0xffff : ((dev) >> 8) & 0xff))
> #define MINOR(dev)      ((unsigned int)(((dev) & 0xffff0000) \
> 	? ((dev) & 0xffff) : ((dev) & 0xff)))
> #define MKDEV(ma,mi)    ((dev_t)((((ma) & ~0xff) == 0 && ((mi) & ~0xff) == 0) \
> 	? (((ma) << 8) | (mi)) : (((ma) << 16) | (mi))))
> 
> This is 1-1 on nonzero majors (and zero major, 8-bit minor).
> 

I thought we had already decided:

	12 bits major : 20 bits minor

The zero major is used for dev_t compatibility, of course.

I personally still prefer 32:32, but I got voted down.

	-hpa
-- 
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