Re: HEADSUP: Change of makedev() semantics.

From: Greg 'groggy' Lehey <>
Date: Mon, 29 Sep 2003 09:29:06 +0930
On Sunday, 28 September 2003 at 19:46:20 -0400, Robert Watson wrote:
> On Mon, 29 Sep 2003, Greg 'groggy' Lehey wrote:
>> On Sunday, 28 September 2003 at 23:22:07 +0200, Poul-Henning Kamp wrote:
>>> Basically:
>>> 	3. If you do a "normal" device driver, cache the result
>>> 	   from when you call make_dev().
>>> ...
>>> 	./dev/vinum
>>> 		Failure to cache result of make_dev() ?
>> Where should this be cached?  Can you point to example code?
> Actually, it looks like Vinum is caching the dev_t's,

Ah, you mean saving the results rather than calling make_dev() every
time?  Yes, it only calls make_dev() once for any device.

> but it's not always using them to get back to the dev_t--sometimes
> it's invoking makedev() instead.  However, this appears to happen
> only in the vinumrevive.c code, so I'm not sure if that's a property
> of the cached reference being unavailable it looks like it should be
> available in that context though.

No, it should always be available.  I was going to say "I don't see
any references to make_dev() in vinumrevive.c, nor any references to
makedev() at all", but I see that VINUM_SD includes both.

> I.e., using sd->dev instead of VINUM_SD() -- it looks like there is
> a valid (struct sd *) reference there to follow, so you can get to
> the dev_t without doing a makedev().

Yes, this is a bug (and an indication of the dangers of using macros :-)
I'll fix it.

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Received on Sun Sep 28 2003 - 14:59:12 UTC

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