linux-kernel - Re: [tpmdd-devel] [PATCH RFC v2 5/5] tpm2: expose resource manager via a device link /dev/tpms<n>

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Date:   Fri, 13 Jan 2017 09:40:08 -0800
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net
Subject: Re: [tpmdd-devel] [PATCH RFC v2 5/5] tpm2: expose resource manager
 via a device link /dev/tpms<n>

On Fri, 2017-01-13 at 10:25 -0700, Jason Gunthorpe wrote:
> On Thu, Jan 12, 2017 at 10:56:28PM +0200, Jarkko Sakkinen wrote:
> 
> > >  dev_t tpm_devt;
> > 
> > But they should have different major device numbers.
> 
> major/minors don't really matter these days since they are dynamic

Right, although we have this weird piece of code:


	if (chip->dev_num == 0)
		chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
	else
		chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

So the first TPM device gets the MISC_MAJOR with TPM_MINOR and the rest
get the dynamic major/minor.  It means when you do an ls on a complex
system you get something like:

crw------- 1 root root  10,   224 Jan 13 06:21 /dev/tpm0
crw------- 1 root root 246,     1 Jan 13 09:38 /dev/tpm1
crw-rw-rw- 1 root root 246, 65536 Jan 13 06:21 /dev/tpms0
crw-rw-rw- 1 root root 246, 65537 Jan 13 09:38 /dev/tpms1

Perhaps it's time just to junk the reserved misc minor?

James