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

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Date:   Mon, 23 Jan 2023 23:10:26 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.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()

Hi,

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).

Regards,

Hans