linux-kernel - Re: [PATCH v1 1/3] ACPI: video: Fix refcounting in apple_gmux_backlight

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Message-ID: <Y8+fWzQP87kGBuJP@smile.fi.intel.com>
Date:   Tue, 24 Jan 2023 11:05:31 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        acpica-devel@...ts.linuxfoundation.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>
Subject: Re: [PATCH v1 1/3] ACPI: video: Fix refcounting in
 apple_gmux_backlight_present()

On Mon, Jan 23, 2023 at 11:10:26PM +0100, Hans de Goede wrote:
> On 1/23/23 19:18, Andy Shevchenko wrote:
> > On Mon, Jan 23, 2023 at 06:46:44PM +0100, Hans de Goede wrote:
> >> On 1/23/23 18:10, Andy Shevchenko wrote:
> >>> acpi_dev_get_first_match_dev() gets ACPI device with the bumped
> >>> refcount. The caller must drop it when it's done.
> >>>
> >>> Fix ACPI device refcounting in apple_gmux_backlight_present().

...

> >> Thank you for your work on this, much appreciated and I like
> >> the new acpi_get_first_match_physical_node().
> >>
> >> But I don't think this patch is a good idea. There is a
> >> regression related to apple_gmux_backlight_present()
> >> with a patch-set fixing it pending.
> >>
> >> And that patch-set actually removes this function. Adding
> >> a fix for this real, but not really important leak now,
> >> will just make backporting the actual fix harder.
> >>
> >> So I would prefer for this patch to not go in and to
> >> go for (a to be submitted v2) of the patch-set fixing
> >> the regression right away instead.
> > 
> > Maybe I missed something, but I noticed that you actually moved (not killed)
> > the code which is currently in this function. If it's the case, I prefer my
> > fix to be imported first.
> 
> The code is not really moved, patch 2/3 of my patch-set factors out
> the detection code from drivers/platform/x86/apple-gmux.c's probe
> function. The new factored out code uses a similar construct as
> the apple_gmux_backlight_present() code (including the same leak).
> 
> Then patch 3/3 drops apple_gmux_backlight_present() and calls
> the new factored out probe code.
> 
> I'll fix the leak in v2 and then add the 3 patches to pdx86/fixes
> for the next pull-req to Linus (thus also fixing the leak).

As agreed with Rafael, thanks!

-- 
With Best Regards,
Andy Shevchenko