linux-kernel - Re: [PATCH 1/7] acpi: add a way to promote/demote vendor backlight drivers

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Message-ID: <20120626221907.GC26614@kamineko.org>
Date:	Wed, 27 Jun 2012 07:19:08 +0900
From:	Mattia Dongili <malattia@...ux.it>
To:	Corentin Chary <corentin.chary@...il.com>
Cc:	Len Brown <lenb@...nel.org>, Matthew Garrett <mjg59@...f.ucam.org>,
	linux-acpi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] acpi: add a way to promote/demote vendor backlight
 drivers

Hi Corentin,

On Wed, Jun 13, 2012 at 09:32:01AM +0200, Corentin Chary wrote:
...
> +/* Promote the vendor interface instead of the generic video module.
> + * This function allow DMI blacklists to be implemented by externals
> + * platform drivers instead of putting a big blacklist in video_detect.c
> + * After calling this function you will probably want to call
> + * acpi_video_unregister() to make sure the video module is not loaded
> + */
> +void acpi_video_dmi_promote_vendor(void)
> +{
> +	acpi_video_caps_check();
> +	acpi_video_support |= ACPI_VIDEO_BACKLIGHT_DMI_VENDOR;
> +}
> +EXPORT_SYMBOL(acpi_video_dmi_promote_vendor);

I think having the promote_vendor() function do the sanity check on the
acpi_backlight parameter and the unregistering of the acpi_video device
may make the code cleaner and more acpi_video-agnostic in the drivers.
I.e. (untested sample code):

bool acpi_video_promote_vendor(void)
{
	if (acpi_video_backlight_support())
		return false;

	acpi_video_support |= ACPI_VIDEO_BACKLIGHT_DMI_VENDOR;
	pr_info("Disabling ACPI video driver\n");
	acpi_video_unregister();
	return true;
}
EXPORT_SYMBOL(acpi_video_promote_vendor);

and in the drivers you do

	if (my_drv->broken_acpi_video) {
		if (acpi_video_promote_vendor())
			do_backlight_init();
	} else if (!acpi_video_backlight_support())
		do_backlight_init();

or something along these lines.
If you give a boolean parameter to acpi_video_promote_vendor to force
vendor backlight we could make the drivers' code even simpler but that
would change the semantics of the "promotion" to something more of a
"take-over".

PS: I will need to promote backlight control in sony-laptop.ko
eventually as well but I don't have a DMI based list but rather I should
look at a specific handle (or say Method) presence in the SNC Device.
I guess I'm just bothered by the function naming here but not a big
deal. :)
-- 
mattia
:wq!
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