linux-kernel - Re: [PATCH] char: misc: Allow minors values up to MINORMASK

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Date:   Fri, 9 Sep 2022 10:42:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     D Scott Phillips <scott@...amperecomputing.com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] char: misc: Allow minors values up to MINORMASK

On Tue, Sep 06, 2022 at 12:52:13PM -0700, D Scott Phillips wrote:
> For per-cpu coresight_tmc devices, we can end up with hundreds of devices
> on large systems that all want a dynamic minor number.  Switch the dynamic
> minors allocator to an ida and add logic to allocate in the ranges [0..127]
> and [256..MINORMASK]. Allocations start from 127 growing downwards and then
> increasing from 256, so device numbering for the first 128 devices should
> be the same as before.
> 
> Signed-off-by: D Scott Phillips <scott@...amperecomputing.com>
> ---
>  drivers/char/misc.c | 41 ++++++++++++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 13 deletions(-)

So you are adding more logic to the kernel for no change at all?

Why is this needed?  What changed here except the underlying data
structure being used?

thanks,

greg k-h