netdev - Re: [PATCH net-next] ptp: dynamic allocation of PHC char devices

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Date:	Wed, 10 Apr 2013 13:49:27 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	bhutchings@...arflare.com
Cc:	jbenc@...hat.com, netdev@...r.kernel.org, richardcochran@...il.com
Subject: Re: [PATCH net-next] ptp: dynamic allocation of PHC char devices

From: Ben Hutchings <bhutchings@...arflare.com>
Date: Wed, 10 Apr 2013 18:37:16 +0100

> On Wed, 2013-04-10 at 12:47 +0200, Jiri Benc wrote:
>> As network adapters supporting PTP are becoming more common, machines with
>> many NICs suddenly have many PHCs, too. The current limit of eight /dev/ptp*
>> char devices (and thus, 8 network interfaces with PHC) is insufficient. Let
>> the ptp driver allocate the char devices dynamically.
>> 
>> The character devices are allocated in chunks. idr is used for tracking
>> minor numbers allocation; the mapping from index to pointer is not used, as
>> it is not needed for posix clocks.
> [...]
> 
> I don't understand why you want to dynamically allocate chunks of minor
> numbers, rather than the full range.  Unused minors don't seem to cost
> anything.

Can't multiple (unrelated) devices carve out minor space in the same
major?  Isn't that why it's designed this way?

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