linux-kernel - RE: [PATCH v5 1/5] usb: Add support for Intel LJCA device

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Date:   Fri, 30 Jun 2023 07:40:48 +0000
From:   "Wu, Wentong" <wentong.wu@...el.com>
To:     "Ye, Xiang" <xiang.ye@...el.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Lee Jones <lee@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        "Matthias Kaehlcke" <mka@...omium.org>,
        Wolfram Sang <wsa@...nel.org>,
        Tyrone Ting <kfting@...oton.com>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
        "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>,
        "Wang, Zhifeng" <zhifeng.wang@...el.com>,
        "Zhang, Lixu" <lixu.zhang@...el.com>
Subject: RE: [PATCH v5 1/5] usb: Add support for Intel LJCA device


> -----Original Message-----
> From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Sent: Wednesday, March 15, 2023 5:10 PM
> 
> On Tue, Mar 14, 2023 at 05:52:52PM +0200, Andy Shevchenko wrote:
> > On Tue, Mar 14, 2023 at 11:38:14PM +0800, Ye, Xiang wrote:
> > > On Tue, Mar 14, 2023 at 10:36:57AM +0200, Heikki Krogerus wrote:
> > > > On Tue, Mar 14, 2023 at 04:03:26PM +0800, Ye, Xiang wrote:
> >
> > ...
> >
> > > > You don't really seem to get any benefit from MFD. Perhaps it
> > > > would be more appropriate and clear if you just registered
> > > > auxiliary devices in this driver. Check drivers/base/auxiliary.c.
> > > Yes, it should be a work. I have a question.
> > > MFD provides the ACPI binding for sub-devices through struct
> > > mfd_cell_acpi_match. But I didn't see this in drivers/base/auxiliary.c.
> > > If using auxiliary bus to implement the LJCA sub-devices, we need to
> > > do the sub-devices acpi binding manually in ljca.c.
> > >
> > > Something Like:
> > > adr = LJCA_ACPI_MATCH_GPIO
> > > adev = acpi_find_child_device(parent, adr, false);
> > > ACPI_COMPANION_SET(&pdev->dev, adev ?: parent);
> > >
> > > Is that acceptable?

This actually doesn't work, look at the acpi_find_child_device(), it compares the
bus address specified by _ADR object, but there is no _ADR object in DSDT for
these three devices because the relationship between the parent and children
isn't bus type listed in ACPI spec, so it always return NULL.

BR,
Wentong 

> 
> Looks ok to me.
> 
> > Maybe you can implement this on the level of auxiliary bus.
> 
> I would actually prefer that the auxiliary bus itself does not make any
> assumptions regarding the whereabouts of the fwnodes at this stage. Maybe
> later, when(if) there are more users.
> 
> thanks,
> 
> --
> heikki