Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit dd97950a authored by Jani Nikula's avatar Jani Nikula
Browse files

drm/i915/bios: add proper documentation for the Video BIOS Table (VBT) 



Add an overview and documentation for the VBT/BDB header structures.

Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/3d826d4600688ca3518713776ab5bd8a8fc9f20f.1450702954.git.jani.nikula@intel.com
parent 0bff4858

Documentation/DocBook/gpu.tmpl

+6 −0
Original line number Diff line number Diff line
@@ -4108,6 +4108,12 @@ int num_ioctls;</synopsis> 
!Pdrivers/gpu/drm/i915/intel_csr.c csr support for dmc

!Idrivers/gpu/drm/i915/intel_csr.c

      </sect2>

      <sect2>

	<title>Video BIOS Table (VBT)</title>

!Pdrivers/gpu/drm/i915/intel_bios.c Video BIOS Table (VBT)

!Idrivers/gpu/drm/i915/intel_bios.c

!Idrivers/gpu/drm/i915/intel_bios.h

      </sect2>

    </sect1>



    <sect1>

drivers/gpu/drm/i915/intel_bios.c

+23 −1
Original line number Diff line number Diff line
@@ -31,6 +31,28 @@ 
#include "i915_drv.h"

#include "intel_bios.h"



/**

 * DOC: Video BIOS Table (VBT)

 *

 * The Video BIOS Table, or VBT, provides platform and board specific

 * configuration information to the driver that is not discoverable or available

 * through other means. The configuration is mostly related to display

 * hardware. The VBT is available via the ACPI OpRegion or, on older systems, in

 * the PCI ROM.

 *

 * The VBT consists of a VBT Header (defined as &struct vbt_header), a BDB

 * Header (&struct bdb_header), and a number of BIOS Data Blocks (BDB) that

 * contain the actual configuration information. The VBT Header, and thus the

 * VBT, begins with "$VBT" signature. The VBT Header contains the offset of the

 * BDB Header. The data blocks are concatenated after the BDB Header. The data

 * blocks have a 1-byte Block ID, 2-byte Block Size, and Block Size bytes of

 * data. (Block 53, the MIPI Sequence Block is an exception.)

 *

 * The driver parses the VBT during load. The relevant information is stored in

 * driver private data for ease of use, and the actual VBT is not read after

 * that.

 */



#define	SLAVE_ADDR1	0x70

#define	SLAVE_ADDR2	0x72
@@ -1285,7 +1307,7 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size) 


/**

 * intel_bios_init - find VBT and initialize settings from the BIOS

 * @dev: DRM device

 * @dev_priv: i915 device instance

 *

 * Loads the Video BIOS and checks that the VBT exists.  Sets scratch registers

 * to appropriate values.

drivers/gpu/drm/i915/intel_bios.h

+28 −10
Original line number Diff line number Diff line
@@ -28,22 +28,40 @@ 
#ifndef _I830_BIOS_H_

#define _I830_BIOS_H_



/**

 * struct vbt_header - VBT Header structure

 * @signature:		VBT signature, always starts with "$VBT"

 * @version:		Version of this structure

 * @header_size:	Size of this structure

 * @vbt_size:		Size of VBT (VBT Header, BDB Header and data blocks)

 * @vbt_checksum:	Checksum

 * @reserved0:		Reserved

 * @bdb_offset:		Offset of &struct bdb_header from beginning of VBT

 * @aim_offset:		Offsets of add-in data blocks from beginning of VBT

 */

struct vbt_header {

	u8 signature[20];		/**< Always starts with 'VBT$' */

	u16 version;			/**< decimal */

	u16 header_size;		/**< in bytes */

	u16 vbt_size;			/**< in bytes */

	u8 signature[20];

	u16 version;

	u16 header_size;

	u16 vbt_size;

	u8 vbt_checksum;

	u8 reserved0;

	u32 bdb_offset;			/**< from beginning of VBT */

	u32 aim_offset[4];		/**< from beginning of VBT */

	u32 bdb_offset;

	u32 aim_offset[4];

} __packed;



/**

 * struct bdb_header - BDB Header structure

 * @signature:		BDB signature "BIOS_DATA_BLOCK"

 * @version:		Version of the data block definitions

 * @header_size:	Size of this structure

 * @bdb_size:		Size of BDB (BDB Header and data blocks)

 */

struct bdb_header {

	u8 signature[16];		/**< Always 'BIOS_DATA_BLOCK' */

	u16 version;			/**< decimal */

	u16 header_size;		/**< in bytes */

	u16 bdb_size;			/**< in bytes */

	u8 signature[16];

	u16 version;

	u16 header_size;

	u16 bdb_size;

} __packed;



/* strictly speaking, this is a "skip" block, but it has interesting info */