linux-kernel - Re: [PATCH] serial: 8250_it8768e: Create iTE IT8768E specific 8250 driver

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Message-ID: <Z4Uxx-qaNDKtO9Xq@smile.fi.intel.com>
Date: Mon, 13 Jan 2025 17:31:19 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: WangYuli <wangyuli@...ontech.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
	Niklas Schnelle <schnelle@...ux.ibm.com>, pnewman@...necttech.com,
	Sunil V L <sunilvl@...tanamicro.com>,
	"Paul E. McKenney" <paulmck@...nel.org>, zhanjun@...ontech.com,
	guanwentao@...ontech.com, Zhuozhen He <hezhuozhen@...ontech.com>,
	Guowei Chen <chenguowei@...ontech.com>
Subject: Re: [PATCH] serial: 8250_it8768e: Create iTE IT8768E specific 8250
 driver

On Mon, Jan 13, 2025 at 02:12:01PM +0100, Arnd Bergmann wrote:
> On Mon, Jan 13, 2025, at 13:20, Andy Shevchenko wrote:
> > On Mon, Jan 13, 2025 at 11:36:08AM +0100, Arnd Bergmann wrote:
> >> On Mon, Jan 13, 2025, at 10:59, Andy Shevchenko wrote:
> >> > On Thu, Jan 09, 2025 at 01:40:14PM +0100, Arnd Bergmann wrote:
> >> >> On Thu, Jan 9, 2025, at 13:08, WangYuli wrote:
> >> >> 
> >> >> Can you explain why this isn't done as part of
> >> >> drivers/tty/serial/8250/8250_pnp.c?
> >> >
> >> > I assume you meant 8250_platform.c. PNP is for devices went through legacy PNP
> >> > enumeration, most likely having IOPORT instead of IOMEM.
> >> 
> >> No, I meant the 8250_pnp.c file.
> >
> > I am puzzled then. How should it work? PNP ID != ACPI HID that's provided in
> > this patch commit message. On top of that, PNP driver uses _legacy_ PMP bus
> > and infrastructure.
> 
> I guess I don't understand enough about ACPI then, I always
> assumed these were the same identifiers. I do see that
> CONFIG_ACPI force-enables CONFIG_PNP, and I see the examples in
> https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/ evice_Configuration.html
> refer to _HID values in the form of "PNP####". 

Check the implementation of the pnp_add_id(), for example.

Besides that PNP device has only 24-bit DMA mask by default,
which is due to legacy DMA controllers.

In any case the differences between PNP IDs and ACPI IDs
are described in the specification.

-- 
With Best Regards,
Andy Shevchenko