Re: [PATCH v1 3/3] soc: aspeed: lpc-pcc: Add PCC controller support

[Andrew Jeffery]

On Mon, 2025-02-17 at 13:00 +0100, Krzysztof Kozlowski wrote:
> On 17/02/2025 12:48, Kevin Chen wrote:
> > +
> > +       pcc->mdev.parent = dev;
> > +       pcc->mdev.minor = MISC_DYNAMIC_MINOR;
> > +       pcc->mdev.name = devm_kasprintf(dev, GFP_KERNEL, "%s%d",
> > DEVICE_NAME,
> > +                                       pcc->mdev_id);
> > +       pcc->mdev.fops = &pcc_fops;
> > +       rc = misc_register(&pcc->mdev);
> > +       if (rc) {
> > +               dev_err(dev, "Couldn't register misc device\n");
> > +               goto err_free_kfifo;
> > +       }
> 
> You cannot expose user-space interfaces from SoC drivers. Use
> appropriate subsystem for this with proper ABI documentation.
> 
> See:
> https://lore.kernel.org/all/bc5118f2-8982-46ff-bc75-d0c71475e909@xxxxxxxxxxxxxxxx/
> and more discussions on LKML

Further, drivers/misc/aspeed-lpc-snoop.c already exists:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9f4f9ae81d0affc182f54dd00285ddb90e0b3ae1

Kevin: Did you consider reworking it?

Nuvoton have a similar capability in their NPCM BMC SoC(s) with the
"BPC" ("BIOS POST Code" controller). There should be some consensus on
the binding and userspace interface.

Andrew