Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from in-kernel API

[PrasannaKumar Muralidharan]

Hi Jason,

On 24 October 2017 at 23:16, Jason Gunthorpe
<jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Oct 24, 2017 at 09:44:30PM +0530, PrasannaKumar Muralidharan wrote:
>
>> I am wondering why it is wrong. Isn't the chip id valid till it is
>> unregistered? If so the rfc is correct. Please explain, may be I am
>> missing something.
>
> The lifetime is a bit complicated, but the general rule in the kernel
> for things like this it to use pointers, not ids, and certainly not
> string ids.
>
> For that patch it could just use container_of to get the chip..
>
> Jason

hwrng requires a unique name for every device. In that patch
"tpm-rng-<chip_num>" is used. chip_num is nothing but dev->dev_num.
This way more than 1 tpm chip can be used as rng provider.
tpm_get_random uses chip_num as its parameter. This is why
chip->dev_num was used.

Is that reasoning correct?

Please feel free to correct me if I am wrong.

Thanks,
PrasannaKumar