Re: [PATCH] crypto: loongson - Select CRYPTO_RNG

[Qunqin Zhao]

在 2026/5/22 下午12:03, Eric Biggers 写道:
> On Fri, May 22, 2026 at 11:41:15AM +0800, Qunqin Zhao wrote:
> > 在 2026/5/22 上午10:57, Eric Biggers 写道:
> > > On Fri, May 22, 2026 at 10:52:42AM +0800, Huacai Chen wrote:
> > > > On Fri, May 22, 2026 at 10:26 AM Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> > > > > This driver registers a rng_alg, so it requires CRYPTO_RNG.
> > > > >
> > > > > Fixes: 766b2d724c8d ("crypto: loongson - add Loongson RNG driver support")
> > > > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > > > Closes: https://lore.kernel.org/oe-kbuild-all/202605201622.qWOiiZTV-lkp@xxxxxxxxx/
> > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> > > > Reviewed-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > > > > ---
> > > > >    drivers/crypto/loongson/Kconfig | 1 +
> > > > >    1 file changed, 1 insertion(+)
> > > By the way, do any of the loongson people have any comment on what they
> > > think the point of this driver is?  It's not registered with the actual
> > To provide an AF_ALG-based random number generation interface for other
> > modules and user-space programs.
> >
> > Thanks,
> >
> > Qunqin
> AF_ALG is a userspace interface; it's not available for in-kernel use.
> If you mean using crypto_rng directly, note that no kernel code actually
> uses it other than the tests, the implementation of AF_ALG, and the
> FIPS-specific code which uses drbg.c specifically.
>
> So, the first half of your justification doesn't make any sense.
>
> As far as the second half: why would a userspace program do that instead
> of just using the regular Linux RNG (/dev/urandom)?
>
> AFAIK, the only reason to use a HW RNG directly is for certification
> reasons.
>
> However, there's also already an interface for that: /dev/hw_random.
>
> So AF_ALG seems completely redundant for this case.

To be honest, I previously assumed that the `hw_random` was designed 
strictly and exclusively for the TRNG mode.

Is it architecturally acceptable or common practice for a PRNG mode to 
utilize `hw_random` as well?

Thanks,

Qunqin

> - Eric