Re: [PATCH 07/32] acpi-video-detect: Rewrite backlight interface selection logic

[Aaron Lu <aaron.lu@intel.com>]

On Wed, Jun 10, 2015 at 03:01:07PM +0200, Hans de Goede wrote:
> Currently we have 2 kernel commandline options + dmi-quirks in 3 places all
> interacting (in interesting ways) to select which which backlight interface
> to use. On the commandline we've acpi_backlight=[video|vendor] and
> video.use_native_backlight=[0|1]. DMI quirks we have in
> acpi/video-detect.c, acpi/video.c and drivers/platform/x86/*.c .
> 
> This commit is the first step to cleaning this up, replacing the 2 cmdline
> options with just acpi_video.backlight=[video|vendor|native|none], and
> adding a new API to video_detect.c to reflect this.

I like backlight=[firmware|platform|raw|none] better, but that would
require to put the selection/quirk logic to backlight core. What do you
think?

Regards,
Aaron

> 
> Follow up commits will also move other related code, like unregistering the
> acpi_video backlight interface if it was registered before other drivers
> which take priority over it are loaded, to video_detect.c where this
> logic really belongs.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/acpi/video_detect.c | 172 +++++++++++++++++++++-----------------------
>  include/acpi/video.h        |  17 +++++
>  2 files changed, 100 insertions(+), 89 deletions(-)
> 
> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
> index 0bc8b98..01c8c46 100644
> --- a/drivers/acpi/video_detect.c
> +++ b/drivers/acpi/video_detect.c
> @@ -1,4 +1,6 @@
>  /*
> + *  Copyright (C) 2015       Red Hat Inc.
> + *                           Hans de Goede <hdegoede@redhat.com>
>   *  Copyright (C) 2008       SuSE Linux Products GmbH
>   *                           Thomas Renninger <trenn@suse.de>
>   *
> @@ -9,28 +11,24 @@
>   * acpi_get_pci_dev() can be called to identify ACPI graphics
>   * devices for which a real graphics card is plugged in
>   *
> - * Now acpi_video_get_capabilities() can be called to check which
> - * capabilities the graphics cards plugged in support. The check for general
> - * video capabilities will be triggered by the first caller of
> - * acpi_video_get_capabilities(NULL); which will happen when the first
> - * backlight switching supporting driver calls:
> - * acpi_video_backlight_support();
> - *
>   * Depending on whether ACPI graphics extensions (cmp. ACPI spec Appendix B)
>   * are available, video.ko should be used to handle the device.
>   *
>   * Otherwise vendor specific drivers like thinkpad_acpi, asus-laptop,
>   * sony_acpi,... can take care about backlight brightness.
>   *
> - * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
> - * this file will not be compiled, acpi_video_get_capabilities() and
> - * acpi_video_backlight_support() will always return 0 and vendor specific
> - * drivers always can handle backlight.
> + * Backlight drivers can use acpi_video_get_backlight_type() to determine
> + * which driver should handle the backlight.
>   *
> + * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
> + * this file will not be compiled and acpi_video_get_backlight_type() will
> + * always return acpi_backlight_vendor.
>   */
>  
> +#include <acpi/video.h>
>  #include <linux/export.h>
>  #include <linux/acpi.h>
> +#include <linux/backlight.h>
>  #include <linux/dmi.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> @@ -38,20 +36,24 @@
>  ACPI_MODULE_NAME("video");
>  #define _COMPONENT		ACPI_VIDEO_COMPONENT
>  
> -static long acpi_video_support;
> -static bool acpi_video_caps_checked;
> +static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
> +static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
>  
>  static char acpi_backlight_str[16];
>  module_param_string(backlight, acpi_backlight_str, 16, 0444);
>  MODULE_PARM_DESC(backlight,
> -	"Select which backlight interface to use [vendor|video]");
> +	"Select which backlight interface to use [vendor|video|native]");
>  
>  static void acpi_video_parse_cmdline(void)
>  {
>  	if (!strcmp("vendor", acpi_backlight_str))
> -		acpi_video_support |= ACPI_VIDEO_BACKLIGHT_FORCE_VENDOR;
> +		acpi_backlight_cmdline = acpi_backlight_vendor;
>  	if (!strcmp("video", acpi_backlight_str))
> -		acpi_video_support |= ACPI_VIDEO_BACKLIGHT_FORCE_VIDEO;
> +		acpi_backlight_cmdline = acpi_backlight_video;
> +	if (!strcmp("native", acpi_backlight_str))
> +		acpi_backlight_cmdline = acpi_backlight_native;
> +	if (!strcmp("none", acpi_backlight_str))
> +		acpi_backlight_cmdline = acpi_backlight_none;
>  }
>  
>  static acpi_status
> @@ -82,7 +84,7 @@ find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
>   * buggy */
>  static int video_detect_force_vendor(const struct dmi_system_id *d)
>  {
> -	acpi_video_support |= ACPI_VIDEO_BACKLIGHT_DMI_VENDOR;
> +	acpi_backlight_dmi = acpi_backlight_vendor;
>  	return 0;
>  }
>  
> @@ -130,99 +132,91 @@ static struct dmi_system_id video_detect_dmi_table[] = {
>  };
>  
>  /*
> - * Returns the video capabilities of a specific ACPI graphics device
> + * Determine which type of backlight interface to use on this system,
> + * First check cmdline, then dmi quirks, then do autodetect.
> + *
> + * The autodetect order is:
> + * 1) Is the acpi-video backlight interface supported ->
> + *  no, use a vendor interface
> + * 2) Is this a win8 "ready" BIOS and do we have a native interface ->
> + *  yes, use a native interface
> + * 3) Else use the acpi-video interface
>   *
> - * if NULL is passed as argument all ACPI devices are enumerated and
> - * all graphics capabilities of physically present devices are
> - * summarized and returned. This is cached and done only once.
> + * Arguably the native on win8 check should be done first, but that would
> + * be a behavior change, which may causes issues.
>   */
> -static long acpi_video_get_capabilities(acpi_handle graphics_handle)
> +enum acpi_backlight_type acpi_video_get_backlight_type(void)
>  {
> -	long caps = 0;
> -	struct acpi_device *tmp_dev;
> -	acpi_status status;
> -
> -	if (acpi_video_caps_checked && graphics_handle == NULL)
> -		return acpi_video_support;
> -
> -	if (!graphics_handle) {
> -		/* Only do the global walk through all graphics devices once */
> -		acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
> -				    ACPI_UINT32_MAX, find_video, NULL,
> -				    &caps, NULL);
> -		/* There might be boot param flags set already... */
> -		acpi_video_support |= caps;
> -		acpi_video_caps_checked = 1;
> -		/* Add blacklists here. Be careful to use the right *DMI* bits
> -		 * to still be able to override logic via boot params, e.g.:
> -		 *
> -		 *   if (dmi_name_in_vendors("XY")) {
> -		 *	acpi_video_support |=
> -		 *		ACPI_VIDEO_BACKLIGHT_DMI_VENDOR;
> -		 *}
> -		 */
> +	static DEFINE_MUTEX(init_mutex);
> +	static bool init_done;
> +	static long video_caps;
>  
> +	/* Parse cmdline, dmi and acpi only once */
> +	mutex_lock(&init_mutex);
> +	if (!init_done) {
> +		acpi_video_parse_cmdline();
>  		dmi_check_system(video_detect_dmi_table);
> -	} else {
> -		status = acpi_bus_get_device(graphics_handle, &tmp_dev);
> -		if (ACPI_FAILURE(status)) {
> -			ACPI_EXCEPTION((AE_INFO, status, "Invalid device"));
> -			return 0;
> -		}
> -		acpi_walk_namespace(ACPI_TYPE_DEVICE, graphics_handle,
> +		acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
>  				    ACPI_UINT32_MAX, find_video, NULL,
> -				    &caps, NULL);
> +				    &video_caps, NULL);
> +		init_done = true;
>  	}
> -	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "We have 0x%lX video support %s %s\n",
> -			  graphics_handle ? caps : acpi_video_support,
> -			  graphics_handle ? "on device " : "in general",
> -			  graphics_handle ? acpi_device_bid(tmp_dev) : ""));
> -	return caps;
> +	mutex_unlock(&init_mutex);
> +
> +	if (acpi_backlight_cmdline != acpi_backlight_undef)
> +		return acpi_backlight_cmdline;
> +
> +	if (acpi_backlight_dmi != acpi_backlight_undef)
> +		return acpi_backlight_dmi;
> +
> +	if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
> +		return acpi_backlight_vendor;
> +
> +	if (acpi_osi_is_win8() && backlight_device_registered(BACKLIGHT_RAW))
> +		return acpi_backlight_native;
> +
> +	return acpi_backlight_video;
>  }
> +EXPORT_SYMBOL(acpi_video_get_backlight_type);
>  
> -static void acpi_video_caps_check(void)
> +/*
> + * Set the preferred backlight interface type based on DMI info.
> + * This function allows DMI blacklists to be implemented by external
> + * platform drivers instead of putting a big blacklist in video_detect.c
> + */
> +void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
>  {
> -	/*
> -	 * We must check whether the ACPI graphics device is physically plugged
> -	 * in. Therefore this must be called after binding PCI and ACPI devices
> -	 */
> -	if (!acpi_video_caps_checked) {
> -		acpi_video_parse_cmdline();
> -		acpi_video_get_capabilities(NULL);
> -	}
> +	acpi_backlight_dmi = type;
>  }
> +EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
>  
> -/* 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
> +/*
> + * Compatiblity function, this is going away as soon as all drivers are
> + * converted to acpi_video_set_dmi_backlight_type().
> + *
> + * Promote the vendor interface instead of the generic video module.
>   * 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;
> +	acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
>  }
>  EXPORT_SYMBOL(acpi_video_dmi_promote_vendor);
>  
> -/* Returns true if video.ko can do backlight switching */
> +/*
> + * Compatiblity function, this is going away as soon as all drivers are
> + * converted to acpi_video_get_backlight_type().
> + *
> + * Returns true if video.ko can do backlight switching.
> + */
>  int acpi_video_backlight_support(void)
>  {
> -	acpi_video_caps_check();
> -
> -	/* First check for boot param -> highest prio */
> -	if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_FORCE_VENDOR)
> -		return 0;
> -	else if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_FORCE_VIDEO)
> -		return 1;
> -
> -	/* Then check for DMI blacklist -> second highest prio */
> -	if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_DMI_VENDOR)
> -		return 0;
> -	else if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_DMI_VIDEO)
> -		return 1;
> -
> -	/* Then go the default way */
> -	return acpi_video_support & ACPI_VIDEO_BACKLIGHT;
> +	/*
> +	 * This is done this way since vendor drivers call this to see
> +	 * if they should load, and we do not want them to load for both
> +	 * the acpi_backlight_video and acpi_backlight_native cases.
> +	 */
> +	return acpi_video_get_backlight_type() != acpi_backlight_vendor;
>  }
>  EXPORT_SYMBOL(acpi_video_backlight_support);
> diff --git a/include/acpi/video.h b/include/acpi/video.h
> index 843ef1a..01b5cc7 100644
> --- a/include/acpi/video.h
> +++ b/include/acpi/video.h
> @@ -16,6 +16,14 @@ struct acpi_device;
>  #define ACPI_VIDEO_DISPLAY_LEGACY_PANEL   0x0110
>  #define ACPI_VIDEO_DISPLAY_LEGACY_TV      0x0200
>  
> +enum acpi_backlight_type {
> +	acpi_backlight_undef = -1,
> +	acpi_backlight_none = 0,
> +	acpi_backlight_video,
> +	acpi_backlight_vendor,
> +	acpi_backlight_native,
> +};
> +
>  #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
>  extern int acpi_video_register(void);
>  extern void acpi_video_unregister(void);
> @@ -23,6 +31,8 @@ extern void acpi_video_unregister_backlight(void);
>  extern int acpi_video_get_edid(struct acpi_device *device, int type,
>  			       int device_id, void **edid);
>  extern bool acpi_video_verify_backlight_support(void);
> +extern enum acpi_backlight_type acpi_video_get_backlight_type(void);
> +extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);
>  #else
>  static inline int acpi_video_register(void) { return 0; }
>  static inline void acpi_video_unregister(void) { return; }
> @@ -33,6 +43,13 @@ static inline int acpi_video_get_edid(struct acpi_device *device, int type,
>  	return -ENODEV;
>  }
>  static inline bool acpi_video_verify_backlight_support(void) { return false; }
> +static inline enum acpi_backlight_type acpi_video_get_backlight_type(void)
> +{
> +	return acpi_backlight_vendor;
> +}
> +static void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
> +{
> +}
>  #endif
>  
>  #endif
> -- 
> 2.4.2
> 
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