On Fri, Jan 13, 2017 at 09:40:08AM -0800, James Bottomley wrote:
> 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:
The TPM has always used a static major/minor for tpm0 and dynamic for
the following. Originally this used a misc_device and did:
} else if (chip->dev_num == 0)
chip->vendor.miscdev.minor = TPM_MINOR;
else
chip->vendor.miscdev.minor = MISC_DYNAMIC_MINOR;
When we moved to struct device the !0 tpms got a dynamic major as
well.
I don't really know what the broad kernel feeling is on historical
major/minor stability - this was mainly continuing what had always
been done in this code for pre-udev userspace compatibility.
Does it harm anything?
Jason
