Add an overview and documentation for the VBT/BDB header structures.
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
Documentation/DocBook/gpu.tmpl | 6 ++++++
drivers/gpu/drm/i915/intel_bios.c | 24 +++++++++++++++++++++++-
drivers/gpu/drm/i915/intel_bios.h | 38 ++++++++++++++++++++++++++++----------
3 files changed, 57 insertions(+), 11 deletions(-)
diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
index 6c6e81a9eaf4..f96a5d467f84 100644
--- a/Documentation/DocBook/gpu.tmpl
+++ b/Documentation/DocBook/gpu.tmpl
@@ -3507,6 +3507,12 @@ 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>
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index eba3e0f87181..d487f602a10e 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -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), 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 "$VBT" signature. The VBT Header contains the offset of the BDB
+ * Header. The data blocks are concatenated after the BDB Header. The data
+ * blocks have a 1-byte Block ID, 2-byte Block Size, and Block Size bytes of
+ * data. (Block 53, the MIPI Sequence Block is an exception.)
+ *
+ * The driver parses the VBT during load. The relevant information is stored in
+ * driver private data for ease of use, and the actual VBT is not read after
+ * that.
+ */
+
#define SLAVE_ADDR1 0x70
#define SLAVE_ADDR2 0x72
@@ -1285,7 +1307,7 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
/**
* intel_bios_init - find VBT and initialize settings from the BIOS
- * @dev: DRM device
+ * @dev_priv: i915 device instance
*
* Loads the Video BIOS and checks that the VBT exists. Sets scratch registers
* to appropriate values.
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index 54eac1003a1e..2dc46a98c332 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -28,22 +28,40 @@
#ifndef _I830_BIOS_H_
#define _I830_BIOS_H_
+/**
+ * struct vbt_header - VBT Header structure
+ * @signature: VBT signature, always starts with "$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 */
--
2.1.4
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