linux-kernel - Re: [RFC PATCHv3 1/4] drivers/otp: add initial support for OTP memory

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Date:	Fri, 25 Mar 2011 18:58:50 -0400
From:	Mike Frysinger <vapier@...too.org>
To:	Jamie Iles <jamie@...ieiles.com>
Cc:	linux-kernel@...r.kernel.org, gregkh@...e.de
Subject: Re: [RFC PATCHv3 1/4] drivers/otp: add initial support for OTP memory

On Fri, Mar 25, 2011 at 18:55, Jamie Iles wrote:
> On Fri, Mar 25, 2011 at 06:50:36PM -0400, Mike Frysinger wrote:
>> On Fri, Mar 25, 2011 at 18:47, Jamie Iles wrote:
>> > On Fri, Mar 25, 2011 at 05:58:05PM -0400, Mike Frysinger wrote:
>> >> On Fri, Mar 25, 2011 at 13:14, Jamie Iles wrote:
>> >> > +static unsigned long registered_otp_map[BITS_TO_LONGS(MAX_OTP_DEVICES)];
>> >> > +static DEFINE_MUTEX(otp_register_mutex);
>> >>
>> >> do we really need this ?  if we let the minor number dictate
>> >> availability, then we can increment until that errors/wraps, and we
>> >> dont need to do any tracking ...
>> >
>> > OK, so it would be nice to get rid of this but afaict we still need to
>> > do some accounting of available minor numbers in the range that we've
>> > allocated.  We could do a simple increment % 255 for the minor number
>> > but if OTP devices are removed at runtime then that may get fragmented
>> > and we would need to do retries of device_register() which feels a bit
>> > too easy to mess up.
>> >
>> > Certainly allocating one major number for OTP devices then allocating
>> > the minors one by one would be much better than what I have now.
>> >
>> > We probably also want it so that if you remove the OTP device that has
>> > had regions called otpaN then reinsert it they doesn't suddenly become
>> > otpbN.
>>
>> yeah that's true.  guess i'll leave it be then ;).
>
> OK, but it still might be worth pruning it down to a single major number
> or is that something worth doing later on if it becomes needed?

i dont think we'll see an explosion of OTP devices where we have to
worry about major # exhaustion.  if that day comes, we'll worry about
things then.

as long as we stick to dynamic device numbers, we have the flexibility
to screw around later.
-mike
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