From dd97950a4cb7218fac38570e2e12c57a2cfd8312 Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Mon, 21 Dec 2015 15:10:52 +0200 Subject: [PATCH] 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: Daniel Vetter Signed-off-by: Jani Nikula Link: http://patchwork.freedesktop.org/patch/msgid/3d826d4600688ca3518713776ab5bd8a8fc9f20f.1450702954.git.jani.nikula@intel.com --- 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 03f01e76add7..0061f22d126d 100644 --- a/Documentation/DocBook/gpu.tmpl +++ b/Documentation/DocBook/gpu.tmpl @@ -4108,6 +4108,12 @@ int num_ioctls; !Pdrivers/gpu/drm/i915/intel_csr.c csr support for dmc !Idrivers/gpu/drm/i915/intel_csr.c + + Video BIOS Table (VBT) +!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 + diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c index eba3e0f87181..b6ccba13779e 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), 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 "$VBT" signature. The VBT Header contains the offset of the + * BDB Header. The data blocks are concatenated after the BDB Header. The data + * blocks have a 1-byte Block ID, 2-byte Block Size, and Block Size bytes of + * data. (Block 53, the MIPI Sequence Block is an exception.) + * + * The driver parses the VBT during load. The relevant information is stored in + * driver private data for ease of use, and the actual VBT is not read after + * that. + */ + #define SLAVE_ADDR1 0x70 #define SLAVE_ADDR2 0x72 @@ -1285,7 +1307,7 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size) /** * intel_bios_init - find VBT and initialize settings from the BIOS - * @dev: DRM device + * @dev_priv: i915 device instance * * Loads the Video BIOS and checks that the VBT exists. Sets scratch registers * to appropriate values. diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h index 54eac1003a1e..2dc46a98c332 100644 --- a/drivers/gpu/drm/i915/intel_bios.h +++ b/drivers/gpu/drm/i915/intel_bios.h @@ -28,22 +28,40 @@ #ifndef _I830_BIOS_H_ #define _I830_BIOS_H_ +/** + * struct vbt_header - VBT Header structure + * @signature: VBT signature, always starts with "$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 */ -- 2.20.1